COSE H. Tschofenig Internet-Draft H-BRS Intended status: Standards Track O. Steele, Ed. Expires: 6 August 2026 Tradeverifyd D. Ajitomi bibital L. Lundblade Security Theory LLC M. Jones Self-Issued Consulting 2 February 2026 Use of Hybrid Public-Key Encryption (HPKE) with CBOR Object Signing and Encryption (COSE) draft-ietf-cose-hpke-21 Abstract This specification defines hybrid public-key encryption (HPKE) for use with CBOR Object Signing and Encryption (COSE). HPKE offers a variant of public-key encryption of arbitrary-sized plaintexts for a recipient public key. HPKE is a general encryption framework utilizing an asymmetric key encapsulation mechanism (KEM), a key derivation function (KDF), and an Authenticated Encryption with Associated Data (AEAD) algorithm. This document defines the use of HPKE with COSE. Authentication for HPKE in COSE is provided by COSE-native security mechanisms or by the pre-shared key authenticated variant of HPKE. Discussion Venues This note is to be removed before publishing as an RFC. Discussion of this document takes place on the CBOR Object Signing and Encryption Working Group mailing list (cose@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/cose/. Source for this draft and an issue tracker can be found at https://github.com/cose-wg/draft-ietf-cose-hpke. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Tschofenig, et al. Expires 6 August 2026 [Page 1] Internet-Draft COSE HPKE February 2026 Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 6 August 2026. Copyright Notice Copyright (c) 2026 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4 3. HPKE for COSE . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4 3.2. HPKE Integrated Encryption Mode . . . . . . . . . . . . . 5 3.3. HPKE Key Encryption Mode . . . . . . . . . . . . . . . . 7 3.3.1. Recipient_structure . . . . . . . . . . . . . . . . . 7 3.3.2. COSE-HPKE Recipient Construction . . . . . . . . . . 8 Tschofenig, et al. Expires 6 August 2026 [Page 2] Internet-Draft COSE HPKE February 2026 3.4. Key Representation . . . . . . . . . . . . . . . . . . . 10 4. Ciphersuite Registration . . . . . . . . . . . . . . . . . . 10 4.1. COSE_Keys for COSE-HPKE Ciphersuites . . . . . . . . . . 13 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.1. COSE HPKE Integrated Encryption Mode . . . . . . . . . . 13 5.2. COSE HPKE Key Encryption Mode . . . . . . . . . . . . . . 15 5.3. Key Representation . . . . . . . . . . . . . . . . . . . 16 5.3.1. Public Key for HPKE-0 . . . . . . . . . . . . . . . . 16 5.3.2. Private Key for HPKE-0 . . . . . . . . . . . . . . . 17 5.3.3. KEM Public Key for HPKE-4 . . . . . . . . . . . . . . 17 6. Security Considerations . . . . . . . . . . . . . . . . . . . 18 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 7.1. COSE Algorithms Registry . . . . . . . . . . . . . . . . 19 7.1.1. HPKE-0 . . . . . . . . . . . . . . . . . . . . . . . 19 7.1.2. HPKE-1 . . . . . . . . . . . . . . . . . . . . . . . 19 7.1.3. HPKE-2 . . . . . . . . . . . . . . . . . . . . . . . 19 7.1.4. HPKE-3 . . . . . . . . . . . . . . . . . . . . . . . 20 7.1.5. HPKE-4 . . . . . . . . . . . . . . . . . . . . . . . 20 7.1.6. HPKE-5 . . . . . . . . . . . . . . . . . . . . . . . 20 7.1.7. HPKE-6 . . . . . . . . . . . . . . . . . . . . . . . 21 7.1.8. HPKE-7 . . . . . . . . . . . . . . . . . . . . . . . 21 7.1.9. HPKE-0-KE . . . . . . . . . . . . . . . . . . . . . . 21 7.1.10. HPKE-1-KE . . . . . . . . . . . . . . . . . . . . . . 22 7.1.11. HPKE-2-KE . . . . . . . . . . . . . . . . . . . . . . 22 7.1.12. HPKE-3-KE . . . . . . . . . . . . . . . . . . . . . . 22 7.1.13. HPKE-4-KE . . . . . . . . . . . . . . . . . . . . . . 23 7.1.14. HPKE-5-KE . . . . . . . . . . . . . . . . . . . . . . 23 7.1.15. HPKE-6-KE . . . . . . . . . . . . . . . . . . . . . . 24 7.1.16. HPKE-7-KE . . . . . . . . . . . . . . . . . . . . . . 24 7.2. COSE Header Parameters . . . . . . . . . . . . . . . . . 24 7.2.1. ek Header Parameter . . . . . . . . . . . . . . . . . 24 7.2.2. psk_id Header Parameter . . . . . . . . . . . . . . . 25 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 8.1. Normative References . . . . . . . . . . . . . . . . . . 25 8.2. Informative References . . . . . . . . . . . . . . . . . 26 Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 26 Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 27 Appendix C. Testvectors . . . . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 75 1. Introduction Hybrid public-key encryption (HPKE) [RFC9180] is a scheme that provides public key encryption of arbitrary-sized plaintexts given a recipient's public key. Tschofenig, et al. Expires 6 August 2026 [Page 3] Internet-Draft COSE HPKE February 2026 This document defines the use of HPKE with COSE ([RFC9052], [RFC9053]) with the single-shot APIs defined in Section 6 of [RFC9180]. Multiple invocations of Open() / Seal() on the same context, as discussed in Section 9.7.1 of [RFC9180] are not supported. 2. Conventions and Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. This specification uses the following abbreviations and terms: * Content-encryption key (CEK), a term defined in CMS [RFC5652]. * Hybrid Public Key Encryption (HPKE) is defined in [RFC9180]. * pkR is the public key of the recipient, as defined in [RFC9180]. * skR is the private key of the recipient, as defined in [RFC9180]. * Key Encapsulation Mechanism (KEM), see [RFC9180]. * Key Derivation Function (KDF), see [RFC9180]. * Authenticated Encryption with Associated Data (AEAD), see [RFC9180]. * Additional Authenticated Data (AAD), see [RFC9180]. 3. HPKE for COSE 3.1. Overview This specification supports two modes of using HPKE in COSE, namely: * HPKE Integrated Encryption mode, where HPKE is used to encrypt the plaintext. This mode can only be used with a single recipient. Section 3.2 provides the details. * HPKE Key Encryption mode, where HPKE is used to encrypt a content encryption key (CEK) and the CEK is subsequently used to encrypt the plaintext. This mode supports multiple recipients. Section 3.3 provides the details. Tschofenig, et al. Expires 6 August 2026 [Page 4] Internet-Draft COSE HPKE February 2026 Distinct algorithm identifiers are defined and registered that are specific to each COSE HPKE mode so that they are fully specified, as required by [RFC9864]. Algorithm identifiers MUST only be used in the COSE HPKE mode that is specified for them. In both cases, the new COSE header parameter 'ek' MUST be present. It contains the encapsulated KEM shared secret. The value of this parameter MUST be the 'enc' value output by the HPKE Seal() operation, as defined in Section 6.1 of [RFC9180]. The 'ek' header parameter MUST be encoded as a CBOR byte string. HPKE defines several authentication modes, as described in Table 1 of [RFC9180]. In COSE HPKE, only 'mode_base' and 'mode_psk' are supported. The mode is 'mode_psk' if the 'psk_id' header parameter is present; otherwise, the mode defaults to 'mode_base'. 'mode_base' is described in Section 5.1.1 of [RFC9180], which only enables encryption to the holder of a given KEM private key. 'mode_psk' is described in Section 5.1.2 of [RFC9180], which authenticates using a pre-shared key. 3.2. HPKE Integrated Encryption Mode This mode applies if the COSE_Encrypt0 structure uses a COSE-HPKE algorithm and has no recipient structure(s). Because COSE-HPKE supports header protection, if the 'alg' parameter is present, it MUST be included in the protected header and MUST be a COSE-HPKE algorithm. Although the use of the 'kid' parameter in COSE_Encrypt0 is discouraged by RFC 9052, this document RECOMMENDS the use of the 'kid' parameter (or other parameters) to explicitly identify the static recipient public key used by the sender. If the COSE_Encrypt0 structure includes a 'kid' parameter, the recipient MAY use it to select the corresponding private key. When encrypting, the inputs to the HPKE Seal operation are set as follows: * kem_id: Depends on the COSE-HPKE algorithm used. * pkR: The recipient public key, converted into an HPKE public key. * kdf_id: Depends on the COSE-HPKE algorithm used. * info: Defaults to the empty string; externally provided information MAY be used instead. Tschofenig, et al. Expires 6 August 2026 [Page 5] Internet-Draft COSE HPKE February 2026 * aad: MUST contain the byte string for the authenticated data structure according to the steps defined in Section 5.3 of RFC 9052. For the Integrated Encryption mode the context string will be "Encrypt0". Externally provided AAD information MAY be provided and MUST be passed into the Enc_structure via the external_aad field. * aead_id: Depends on the COSE-HPKE algorithm used. * pt: The raw message plaintext. The outputs are used as follows: * enc: MUST be placed raw into the 'ek' (encapsulated key) parameter in the unprotected bucket. * ct: MUST be used as layer ciphertext. If not using detached content, this is directly placed as ciphertext in COSE_Encrypt0 structure. Otherwise, it is transported separately and the ciphertext field is nil. See Section 5 of [RFC9052] for a description of detached payloads. If 'mode_psk' has been selected, then the 'psk_id' parameter MUST be present. If 'mode_base' has been chosen, then the 'psk_id' parameter MUST NOT be present. When decrypting, the inputs to the HPKE Open operation are set as follows: * kem_id: Depends on the COSE-HPKE algorithm used. * skR: The recipient private key, converted into an HPKE private key. * kdf_id: Depends on the COSE-HPKE algorithm used. * aead_id: Depends on the COSE-HPKE algorithm used. * info: Defaults to the empty string; externally provided information MAY be used instead. * aad: MUST contain the byte string for the authenticated data structure according to the steps defined in Section 5.3 of RFC 9052. For the Integrated Encryption mode the context string will be "Encrypt0". Externally provided AAD information MAY be provided and MUST be passed into the Enc_structure via the external_aad field. Tschofenig, et al. Expires 6 August 2026 [Page 6] Internet-Draft COSE HPKE February 2026 * enc: The contents of the layer 'ek' parameter. * ct: The contents of the layer ciphertext. The plaintext output is the raw message plaintext. The COSE_Encrypt0 MAY be tagged or untagged. An example is shown in Section 5.1. 3.3. HPKE Key Encryption Mode This mode is selected if the COSE_recipient structure uses a COSE- HPKE algorithm. In this approach the following layers are involved: * Layer 0 (corresponding to the COSE_Encrypt structure) contains the content (plaintext) encrypted with the CEK. This ciphertext may be detached, and if not detached, then it is included in the COSE_Encrypt structure. * Layer 1 (corresponding to a recipient structure) contains parameters needed for HPKE to generate a shared secret used to encrypt the CEK. This layer conveys the encrypted CEK in the COSE_recipient structure using a COSE-HPKE algorithm. The unprotected header MAY contain the kid parameter to identify the static recipient public key that the sender has been using with HPKE. This two-layer structure is used to encrypt content that can also be shared with multiple parties at the expense of a single additional encryption operation. As stated above, the specification uses a CEK to encrypt the content at layer 0. 3.3.1. Recipient_structure This section defines the Recipient_structure, which is used in place of COSE_KDF_Context for COSE-HPKE recipients. It MUST be used for COSE-HPKE recipients, as it provides integrity protection for recipient-protected header parameters. The Recipient_structure is modeled after the Enc_structure defined in [RFC9052], but is specific to COSE_recipient structures and MUST NOT be used with COSE_Encrypt. Furthermore, the use of COSE_KDF_Context is prohibited in COSE-HPKE; it MUST NOT be used. Tschofenig, et al. Expires 6 August 2026 [Page 7] Internet-Draft COSE HPKE February 2026 Recipient_structure = [ context: "HPKE Recipient", next_layer_alg: int/tstr, recipient_protected_header: empty_or_serialize_map, recipient_extra_info: bstr ] * "next_layer_alg" is the algorithm ID of the COSE layer for which the COSE_recipient is encrypting a key. It is the algorithm that the key MUST be used with. This value MUST match the alg parameter in the next lower COSE layer. (This serves the same purpose as the alg ID in the COSE_KDF_Context. It also mitigates attacks where the attacker manipulates the content-encryption algorithm identifier. This attack has been demonstrated against CMS and the mitigation can be found in [I-D.ietf-lamps-cms-cek-hkdf-sha256]. * "recipient_protected_header" contains the protected header parameters from the COSE_recipient CBOR-encoded deterministically with the "Core Deterministic Encoding Requirements", specified in Section 4.2.1 of [RFC8949]. * "recipient_extra_info" contains any additional context the application wishes to include in the key derivation via the HPKE info parameter. If none, it is a zero-length string. 3.3.2. COSE-HPKE Recipient Construction Because COSE-HPKE supports header protection, if the 'alg' parameter is present, it MUST be in the protected header parameters and MUST be a COSE-HPKE algorithm. The protected header MAY contain the kid parameter to identify the static recipient public key that the sender used. Use of the 'kid' parameter is RECOMMENDED to explicitly identify the static recipient public key used by the sender. Including it in the protected header parameters ensures that it is input into the key derivation function of HPKE. When encrypting, the inputs to the HPKE Seal operation are set as follows: * kem_id: Depends on the COSE-HPKE algorithm used. * pkR: The recipient public key, converted into HPKE public key. * kdf_id: Depends on the COSE-HPKE algorithm used. Tschofenig, et al. Expires 6 August 2026 [Page 8] Internet-Draft COSE HPKE February 2026 * aead_id: Depends on the COSE-HPKE algorithm used. * info: Deterministic encoding of the Recipient_structure. Externally provided context information MAY be provided and MUST be passed into the Recipient_structure via the recipient_extra_info field. * aad: Defaults to the empty string; externally provided information MAY be used instead. * pt: The raw key for the next layer down. The outputs are used as follows: * enc: MUST be placed raw into the 'ek' (encapsulated key) parameter in the unprotected bucket. * ct: MUST be placed raw in the ciphertext field in the COSE_recipient. When decrypting, the inputs to the HPKE Open operation are set as follows: * kem_id: Depends on the COSE-HPKE algorithm used. * skR: The recipient private key, converted into HPKE private key. * kdf_id: Depends on the COSE-HPKE algorithm used. * aead_id: Depends on the COSE-HPKE algorithm used. * info: Deterministic encoding of the Recipient_structure. Externally provided context information MAY be provided and MUST be passed into the Recipient_structure via the recipient_extra_info field. * aad: Defaults to the empty string; externally provided information MAY be used instead. * ct: The contents of the layer ciphertext field. The plaintext output is the raw key for the next layer down. Tschofenig, et al. Expires 6 August 2026 [Page 9] Internet-Draft COSE HPKE February 2026 It is not necessary to populate recipient_aad, as HPKE inherently mitigates the classes of attacks that COSE_KDF_Context, and SP800-56A are designed to address. COSE-HPKE use cases may still utilize recipient_aad for other purposes as needed; however, it is generally intended for small values such as identifiers, contextual information, or secrets. It is not designed for protecting large or bulk external data. Any bulk external data that requires protection should be handled at layer 0 using external_aad. The COSE_recipient structure is computed for each recipient. When encrypting the content at layer 0, the instructions in Section 5.3 of [RFC9052] MUST be followed, including the calculation of the authenticated data structure. An example is shown in Section 5.2. 3.4. Key Representation The COSE_Key with the existing key types can be used to represent KEM private or public keys. When using a COSE_Key for COSE-HPKE, the following checks are made: * If the "kty" field is "AKP", then the public and private keys SHALL be the raw HPKE public and private keys (respectively) for the KEM used by the algorithm. * Otherwise, the key MUST be suitable for the KEM used by the algorithm. In case the "kty" parameter is "EC2" or "OKP", this means the value of "crv" parameter is suitable. The valid combinations of KEM, "kty" and "crv" for the algorithms defined in this document are shown in Figure 1. * If the "key_ops" field is present, it MUST include only "derive bits" for the private key and MUST be empty for the public key. Examples of the COSE_Key for COSE-HPKE are shown in Section 5.3. 4. Ciphersuite Registration A ciphersuite is a group of algorithms, often sharing component algorithms such as hash functions, targeting a security level. A COSE-HPKE algorithm is composed of the following choices: * COSE HPKE Mode Tschofenig, et al. Expires 6 August 2026 [Page 10] Internet-Draft COSE HPKE February 2026 * KEM Algorithm * KDF Algorithm * AEAD Algorithm The "KEM", "KDF", and "AEAD" values are chosen from the HPKE IANA registry [HPKE-IANA]. The HPKE mode is determined by the presence or absence of the 'psk_id' parameter and is therefore not explicitly indicated in the ciphersuite. For a list of ciphersuite registrations, please see Section 7. The following table summarizes the relationship between the ciphersuites registered in this document and the values registered in the HPKE IANA registry [HPKE-IANA]. +-------------------+-----------------------+-------------------+ | COSE-HPKE | COSE HPKE Mode | HPKE | | Ciphersuite Label | | KEM | KDF | AEAD | +-------------------+-----------------------+------+-----+------+ | HPKE-0 | Integrated Encryption | 0x10 | 0x1 | 0x1 | | HPKE-1 | Integrated Encryption | 0x11 | 0x2 | 0x2 | | HPKE-2 | Integrated Encryption | 0x12 | 0x3 | 0x2 | | HPKE-3 | Integrated Encryption | 0x20 | 0x1 | 0x1 | | HPKE-4 | Integrated Encryption | 0x20 | 0x1 | 0x3 | | HPKE-5 | Integrated Encryption | 0x21 | 0x3 | 0x2 | | HPKE-6 | Integrated Encryption | 0x21 | 0x3 | 0x3 | | HPKE-7 | Integrated Encryption | 0x10 | 0x1 | 0x2 | | HPKE-0-KE | Key Encryption | 0x10 | 0x1 | 0x1 | | HPKE-1-KE | Key Encryption | 0x11 | 0x2 | 0x2 | | HPKE-2-KE | Key Encryption | 0x12 | 0x3 | 0x2 | | HPKE-3-KE | Key Encryption | 0x20 | 0x1 | 0x1 | | HPKE-4-KE | Key Encryption | 0x20 | 0x1 | 0x3 | | HPKE-5-KE | Key Encryption | 0x21 | 0x3 | 0x2 | | HPKE-6-KE | Key Encryption | 0x21 | 0x3 | 0x3 | | HPKE-7-KE | Key Encryption | 0x10 | 0x1 | 0x2 | +-------------------+-----------------------+------+-----+------+ The following list maps the ciphersuite labels to their textual description. * HPKE-0: Integrated Encryption with DHKEM(P-256, HKDF-SHA256) KEM, HKDF-SHA256 KDF, and AES-128-GCM AEAD. * HPKE-1: Integrated Encryption with DHKEM(P-384, HKDF-SHA384) KEM, HKDF-SHA384 KDF, and AES-256-GCM AEAD. Tschofenig, et al. Expires 6 August 2026 [Page 11] Internet-Draft COSE HPKE February 2026 * HPKE-2: Integrated Encryption with DHKEM(P-521, HKDF-SHA512) KEM, HKDF-SHA512 KDF, and AES-256-GCM AEAD. * HPKE-3: Integrated Encryption with DHKEM(X25519, HKDF-SHA256) KEM, HKDF-SHA256 KDF, and AES-128-GCM AEAD. * HPKE-4: Integrated Encryption with DHKEM(X25519, HKDF-SHA256) KEM, HKDF-SHA256 KDF, and ChaCha20Poly1305 AEAD. * HPKE-5: Integrated Encryption with DHKEM(X448, HKDF-SHA512) KEM, HKDF-SHA512 KDF, and AES-256-GCM AEAD. * HPKE-6: Integrated Encryption with DHKEM(X448, HKDF-SHA512) KEM, HKDF-SHA512 KDF, and ChaCha20Poly1305 AEAD. * HPKE-7: Integrated Encryption with DHKEM(P-256, HKDF-SHA256) KEM, HKDF-SHA256 KDF, and AES-256-GCM AEAD. * HPKE-0: Key Encryption with DHKEM(P-256, HKDF-SHA256) KEM, HKDF- SHA256 KDF, and AES-128-GCM AEAD. * HPKE-1: Key Encryption with DHKEM(P-384, HKDF-SHA384) KEM, HKDF- SHA384 KDF, and AES-256-GCM AEAD. * HPKE-2: Key Encryption with DHKEM(P-521, HKDF-SHA512) KEM, HKDF- SHA512 KDF, and AES-256-GCM AEAD. * HPKE-3: Key Encryption with DHKEM(X25519, HKDF-SHA256) KEM, HKDF- SHA256 KDF, and AES-128-GCM AEAD. * HPKE-4: Key Encryption with DHKEM(X25519, HKDF-SHA256) KEM, HKDF- SHA256 KDF, and ChaCha20Poly1305 AEAD. * HPKE-5: Key Encryption with DHKEM(X448, HKDF-SHA512) KEM, HKDF- SHA512 KDF, and AES-256-GCM AEAD. * HPKE-6: Key Encryption with DHKEM(X448, HKDF-SHA512) KEM, HKDF- SHA512 KDF, and ChaCha20Poly1305 AEAD. * HPKE-7: Key Encryption with DHKEM(P-256, HKDF-SHA256) KEM, HKDF- SHA256 KDF, and AES-256-GCM AEAD. As the list indicates, the ciphersuite labels have been abbreviated at least to some extent to strike a balance between readability and length. Tschofenig, et al. Expires 6 August 2026 [Page 12] Internet-Draft COSE HPKE February 2026 The ciphersuite list above is a minimal starting point. Additional ciphersuites can be registered into the already existing registry. For example, once post-quantum cryptographic algorithms have been standardized it might be beneficial to register ciphersuites for use with COSE-HPKE. Additionally, ciphersuites utilizing the compact encoding of the public keys, as defined in [I-D.irtf-cfrg-dnhpke], may be standardized for use in constrained environments. As a guideline for ciphersuite submissions to the IANA COSE algorithm registry, the designated experts must only register combinations of (KEM, KDF, AEAD) triple that constitute valid combinations for use with HPKE, the KDF used should (if possible) match one internally used by the KEM, and components should not be mixed between global and national standards. 4.1. COSE_Keys for COSE-HPKE Ciphersuites The COSE-HPKE algorithm uniquely determines the KEM for which a COSE_Key is used. The following mapping table shows the valid combinations of the KEM used, COSE_Key type, and its curve/key subtype. This holds for COSE algorithms using either of the COSE HPKE modes (Integrated Encryption and Key Encryption). +---------------------+--------------+ | HPKE KEM id | COSE_Key | | | kty | crv | +---------------------+-----+--------+ | 0x0010, 0x0013 | EC2 | P-256 | | 0x0011, 0x0014 | EC2 | P-384 | | 0x0012, 0x0015 | EC2 | P-521 | | 0x0020 | OKP | X25519 | | 0x0021 | OKP | X448 | +---------------------+-----+--------+ Figure 1: COSE_Key Types and Curves for COSE-HPKE Ciphersuites 5. Examples This section provides a set of examples that show the HPKE Integrated Encryption Mode and the HPKE Key Encryption Mode, and illustrates the use of key representations for HPKE KEM. 5.1. COSE HPKE Integrated Encryption Mode This example assumes that a sender wants to communicate an encrypted payload to a single recipient, named "bob". Tschofenig, et al. Expires 6 August 2026 [Page 13] Internet-Draft COSE HPKE February 2026 An example of the HPKE Integrated Encryption Mode is shown in Figure 3. Line breaks and comments have been inserted for better readability. This example uses the following: * Suite: HPKE-0 (P-256 / HKDF-SHA256 / AES-128-GCM) * Plaintext: "This is the content." * External AAD: empty * External Info: empty * Recipient kid: "bob" The ciphertext (hex) transmitted to "bob" is: d08344a1011823a20443626f622358410457229bdd99407b384a9e59fa15 53224d58b106e9ebebdaa06d2126bd96757674847669966ecb0dcdf21af5 623f19f0b799b0cddf3ee930b739dd474f6282de0158253f3c1595e9d252 e816215a9ce73f47ba4b57acb06ecc39ca5a03a14108bbe7807af5688d61 Figure 2: Hex-Encoding of COSE_Encrypt0 COSE_Encrypt0 pretty-printed: 16([ h'A1011823', { 4: 'bob', -4: h'0457229BDD99407B384A9E59FA1553224D58B106E9EBEBDA A06D2126BD96757674847669966ECB0DCDF21AF5623F19F0B799B0 CDDF3EE930B739DD474F6282DE01' }, h'3F3C1595E9D252E816215A9CE73F47BA4B57ACB06ECC39CA5A03A1 4108BBE7807AF5688D61' ]) Figure 3: COSE_Encrypt0 Example for HPKE The following COSE Key was used in this example: Tschofenig, et al. Expires 6 August 2026 [Page 14] Internet-Draft COSE HPKE February 2026 { 1 /kty/: 2, 2 /kid/: h'626f62', 3 /alg/: 35 /HPKE-0 (P-256 + HKDF-SHA256 + AES-128-GCM)/, -1 /crv/: 1 /P-256/, -2 /x/: h'02a8e3315f96bc7355dbf85740c6d8e53fb070cd8ba5c419be49a91d789ef55c', -3 /y/: h'96b6621abf5ca532e042dc5c346c1ef0c9186b83cb122e50a46f1458de023d35', -4 /d/: h'eca39300147c91a2a65d17e00ea278b57a14178245bf5686d9a404cca1816b8e' } Figure 4: COSE Key 5.2. COSE HPKE Key Encryption Mode An example of key encryption using the COSE_Encrypt structure using HPKE is shown in below. Line breaks and comments have been inserted for better readability. This example uses the following input parameters: * Content encryption algorithm: AES-128-GCM * plaintext: "This is the content." * kid:"bob" * alg: HPKE-0-KE (assumed 46) - Key Encryption, DHKEM(P-256, HKDF- SHA256), KDF: HKDF-SHA256, AEAD: AES-128-GCM * external aad and info are empty The following COSE Key is used: a701020243626f6203182e2001215820d832916778598ea6203af974c97b 45970ac0266fc6a3b7f213ba9f8b591b92972258208d9410599a8e83d00e b46d67b34d4dac8fbd4b8b1f08864599659cee9ef09184235820b1162c56 8efcba91c8e4e82f66e36b45aa10bc55228cf65ecd3bb29cfb09f989 As a pretty-printed version: Tschofenig, et al. Expires 6 August 2026 [Page 15] Internet-Draft COSE HPKE February 2026 { 1 /kty/: 2, 2 /kid/: h'626f62' /"bob"/, 3 /alg/: 46 /HPKE-0-KE/, -1 /crv/: 1 /P-256/, -2 /x/: h'd832916778598ea6203af974c97b45970ac0266fc6a3b7f213ba9 f8b591b9297', -3 /y/: h'8d9410599a8e83d00eb46d67b34d4dac8fbd4b8b1f08864599659c ee9ef09184', -4 /d/: h'b1162c568efcba91c8e4e82f66e36b45aa10bc55228cf65ecd3bb2 9cfb09f989' } As a result, the following COSE_Encrypt payload is produced: d8608443a10101a1055089115f10ecc1c7fd834442cb87929bc15825534d b92f5366e3cadd096774a9576bb8d8867e75ea38c329ecfc7b8793c5a4ae 9603e5b0b6818349a201182e0443626f62a12358410417cd85837981ddb1 4963061ab5fb7308988eb922f87cf6cf6ef83556f7657922c9815947e41b 9bc932e48c6f1c4677d9a5506a30d694587628b5193a4cde2f3f58204b50 8a340e463c317f4e62fb8d08c887cac4788087ad022562d05855a50ca4a0 Pretty-printed, this hex-sequence has the following content: 96([ h'A10101', {5: h'89115F10ECC1C7FD834442CB87929BC1'}, h'534DB92F5366E3CADD096774A9576BB8D8867E75EA38C329ECFC7B87 93C5A4AE9603E5B0B6', [ [ h'A201182E0443626F62', {-4: h'0417CD85837981DDB14963061AB5FB7308988EB922F87CF6C F6EF83556F7657922C9815947E41B9BC932E48C6F1C4677D9A5506A3 0D694587628B5193A4CDE2F3F'}, h'4B508A340E463C317F4E62FB8D08C887CAC4788087AD022562D058 55A50CA4A0']] ]) 5.3. Key Representation Examples of private and public KEM key representation are shown below. 5.3.1. Public Key for HPKE-0 Tschofenig, et al. Expires 6 August 2026 [Page 16] Internet-Draft COSE HPKE February 2026 { / kty = 'EC2' / 1: 2, / kid = '01' / 2: h'3031', / alg = HPKE-0 (Assumed: 35) / 3: 35, / crv = 'P-256' / -1: 1, / x / -2: h'65eda5a12577c2bae829437fe338701a10aaa375 e1bb5b5de108de439c08551d', / y / -3: h'1e52ed75701163f7f9e40ddf9f341b3dc9ba860af 7e0ca7ca7e9eecd0084d19c' } Figure 5: Public Key Representation Example for HPKE-0 5.3.2. Private Key for HPKE-0 { / kty = 'EC2' / 1: 2, / kid = '01' / 2: h'3031', / alg = HPKE-0 (Assumed: 35) / 3: 35, / key_ops = ['derive_bits'] / 4: [8], / crv = 'P-256' / -1: 1, / x / -2: h'bac5b11cad8f99f9c72b05cf4b9e26d244dc189f7 45228255a219a86d6a09eff', / y / -3: h'20138bf82dc1b6d562be0fa54ab7804a3a64b6d72 ccfed6b6fb6ed28bbfc117e', / d / -4: h'57c92077664146e876760c9520d054aa93c3afb04 e306705db6090308507b4d3', } Figure 6: Private Key Representation Example for HPKE-0 5.3.3. KEM Public Key for HPKE-4 Tschofenig, et al. Expires 6 August 2026 [Page 17] Internet-Draft COSE HPKE February 2026 { / kty = 'OKP' / 1: 1, / kid = '11' / 2: h'3131', / alg = HPKE-4 (Assumed: 42) / 3: 42, / crv = 'X25519' / -1: 4, / x / -2: h'cb7c09ab7b973c77a808ee05b9bbd373b55c06eaa 9bd4ad2bd4e9931b1c34c22', } Figure 7: Public Key Representation Example for HPKE-4 6. Security Considerations This specification is based on HPKE and the security considerations of [RFC9180] are therefore applicable also to this specification. Both HPKE and HPKE COSE assume that the sender possesses the recipient's public key. Therefore, some form of public key distribution mechanism is assumed to exist, but this is outside the scope of this document. HPKE relies on a source of randomness to be available on the device. Additionally, with the two layer structure the CEK is randomly generated and it MUST be ensured that the guidelines in [RFC8937] for random number generation are followed. HPKE in Base mode does not offer authentication as part of the HPKE KEM. In this case COSE constructs like COSE_Sign, COSE_Sign1, COSE_Mac, or COSE_Mac0 can be used to add authentication. If COSE_Encrypt or COSE_Encrypt0 is used with a detached ciphertext then the subsequently applied integrity protection via COSE_Sign, COSE_Sign1, COSE_Mac, or COSE_Mac0 does not cover this detached ciphertext. Implementers MUST ensure that the detached ciphertext also experiences integrity protection. This is, for example, the case when an AEAD cipher is used to produce the detached ciphertext but may not be guaranteed by non-AEAD ciphers. 7. IANA Considerations This document requests IANA to add new values to the 'COSE Algorithms' and to the 'COSE Header Parameters' registries. Tschofenig, et al. Expires 6 August 2026 [Page 18] Internet-Draft COSE HPKE February 2026 7.1. COSE Algorithms Registry 7.1.1. HPKE-0 * Name: HPKE-0 * Value: TBD1 (Assumed: 35) * Description: COSE HPKE Integrated Encryption using DHKEM(P-256, HKDF-SHA256) KEM, HKDF-SHA256 KDF, and AES-128-GCM AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.2. HPKE-1 * Name: HPKE-1 * Value: TBD3 (Assumed: 37) * Description: COSE HPKE Integrated Encryption using DHKEM(P-384, HKDF-SHA384) KEM, HKDF-SHA384 KDF, and AES-256-GCM AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.3. HPKE-2 * Name: HPKE-2 * Value: TBD5 (Assumed: 39) * Description: COSE HPKE Integrated Encryption using DHKEM(P-521, HKDF-SHA512) KEM, HKDF-SHA512 KDF, and AES-256-GCM AEAD. * Capabilities: [kty] * Change Controller: IESG Tschofenig, et al. Expires 6 August 2026 [Page 19] Internet-Draft COSE HPKE February 2026 * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.4. HPKE-3 * Name: HPKE-3 * Value: TBD7 (Assumed: 41) * Description: COSE HPKE Integrated Encryption using DHKEM(X25519, HKDF-SHA256) KEM, HKDF-SHA256 KDF, and AES-128-GCM AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.5. HPKE-4 * Name: HPKE-4 * Value: TBD8 (Assumed: 42) * Description: COSE HPKE Integrated Encryption using DHKEM(X25519, HKDF-SHA256) KEM, HKDF-SHA256 KDF, and ChaCha20Poly1305 AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.6. HPKE-5 * Name: HPKE-5 * Value: TBD9 (Assumed: 43) * Description: COSE HPKE Integrated Encryption using DHKEM(X448, HKDF-SHA512) KEM, HKDF-SHA512 KDF, and AES-256-GCM AEAD. * Capabilities: [kty] Tschofenig, et al. Expires 6 August 2026 [Page 20] Internet-Draft COSE HPKE February 2026 * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.7. HPKE-6 * Name: HPKE-6 * Value: TBD10 (Assumed: 44) * Description: COSE HPKE Integrated Encryption using DHKEM(X448, HKDF-SHA512) KEM, HKDF-SHA512 KDF, and ChaCha20Poly1305 AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.8. HPKE-7 * Name: HPKE-7 * Value: TBD13 (Assumed: 45) * Description: COSE HPKE Integrated Encryption using DHKEM(P-256, HKDF-SHA256) KEM, HKDF-SHA256 KDF, and AES-256-GCM AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.9. HPKE-0-KE * Name: HPKE-0-KE * Value: TBD14 (Assumed: 46) * Description: COSE HPKE Key Encryption using DHKEM(P-256, HKDF- SHA256) KEM, HKDF-SHA256 KDF, and AES-128-GCM AEAD. Tschofenig, et al. Expires 6 August 2026 [Page 21] Internet-Draft COSE HPKE February 2026 * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.10. HPKE-1-KE * Name: HPKE-1-KE * Value: TBD15 (Assumed: 47) * Description: COSE HPKE Key Encryption using DHKEM(P-384, HKDF- SHA384) KEM, HKDF-SHA384 KDF, and AES-256-GCM AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.11. HPKE-2-KE * Name: HPKE-2-KE * Value: TBD16 (Assumed: 48) * Description: COSE HPKE Key Encryption using DHKEM(P-521, HKDF- SHA512) KEM, HKDF-SHA512 KDF, and AES-256-GCM AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.12. HPKE-3-KE * Name: HPKE-3-KE * Value: TBD17 (Assumed: 49) Tschofenig, et al. Expires 6 August 2026 [Page 22] Internet-Draft COSE HPKE February 2026 * Description: COSE HPKE Key Encryption using DHKEM(X25519, HKDF- SHA256) KEM, HKDF-SHA256 KDF, and AES-128-GCM AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.13. HPKE-4-KE * Name: HPKE-4-KE * Value: TBD18 (Assumed: 50) * Description: COSE HPKE Key Encryption using DHKEM(X25519, HKDF- SHA256) KEM, HKDF-SHA256 KDF, and ChaCha20Poly1305 AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.14. HPKE-5-KE * Name: HPKE-5-KE * Value: TBD19 (Assumed: 51) * Description: COSE HPKE Key Encryption using DHKEM(X448, HKDF- SHA512) KEM, HKDF-SHA512 KDF, and AES-256-GCM AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes Tschofenig, et al. Expires 6 August 2026 [Page 23] Internet-Draft COSE HPKE February 2026 7.1.15. HPKE-6-KE * Name: HPKE-6-KE * Value: TBD20 (Assumed: 52) * Description: COSE HPKE Key Encryption using DHKEM(X448, HKDF- SHA512) KEM, HKDF-SHA512 KDF, and ChaCha20Poly1305 AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.1.16. HPKE-7-KE * Name: HPKE-7-KE * Value: TBD21 (Assumed: 53) * Description: COSE HPKE Key Encryption using DHKEM(P-256, HKDF- SHA256) KEM, HKDF-SHA256 KDF, and AES-256-GCM AEAD. * Capabilities: [kty] * Change Controller: IESG * Reference: [[TBD: This RFC]] * Recommended: Yes 7.2. COSE Header Parameters 7.2.1. ek Header Parameter * Name: ek * Label: TBD11 (Assumed: -4) * Value type: bstr * Value Registry: N/A * Description: HPKE encapsulated key Tschofenig, et al. Expires 6 August 2026 [Page 24] Internet-Draft COSE HPKE February 2026 * Reference: [[TBD: This RFC]] 7.2.2. psk_id Header Parameter * Name: psk_id * Label: TBD12 (Assumed: -5) * Value type: bstr * Value Registry: N/A * Description: A key identifier (kid) for the pre-shared key as defined in Section 5.1.2 of [RFC9180] * Reference: [[TBD: This RFC]] 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", STD 94, RFC 8949, DOI 10.17487/RFC8949, December 2020, . [RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE): Structures and Process", STD 96, RFC 9052, DOI 10.17487/RFC9052, August 2022, . [RFC9053] Schaad, J., "CBOR Object Signing and Encryption (COSE): Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053, August 2022, . [RFC9180] Barnes, R., Bhargavan, K., Lipp, B., and C. Wood, "Hybrid Public Key Encryption", RFC 9180, DOI 10.17487/RFC9180, February 2022, . Tschofenig, et al. Expires 6 August 2026 [Page 25] Internet-Draft COSE HPKE February 2026 8.2. Informative References [HPKE-IANA] IANA, "Hybrid Public Key Encryption (HPKE) IANA Registry", October 2023, . [I-D.ietf-lamps-cms-cek-hkdf-sha256] Housley, R., "Encryption Key Derivation in the Cryptographic Message Syntax (CMS) using HKDF with SHA- 256", Work in Progress, Internet-Draft, draft-ietf-lamps- cms-cek-hkdf-sha256-05, 19 September 2024, . [I-D.irtf-cfrg-dnhpke] Harkins, D., "Deterministic Nonce-less Hybrid Public Key Encryption", Work in Progress, Internet-Draft, draft-irtf- cfrg-dnhpke-07, 16 October 2025, . [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, DOI 10.17487/RFC5652, September 2009, . [RFC8937] Cremers, C., Garratt, L., Smyshlyaev, S., Sullivan, N., and C. Wood, "Randomness Improvements for Security Protocols", RFC 8937, DOI 10.17487/RFC8937, October 2020, . [RFC9864] Jones, M.B. and O. Steele, "Fully-Specified Algorithms for JSON Object Signing and Encryption (JOSE) and CBOR Object Signing and Encryption (COSE)", RFC 9864, DOI 10.17487/RFC9864, October 2025, . Appendix A. Contributors We would like to thank the following individuals for their contributions to the design of embedding the HPKE output into the COSE structure following a long and lively mailing list discussion: * Richard Barnes * Ilari Liusvaara Tschofenig, et al. Expires 6 August 2026 [Page 26] Internet-Draft COSE HPKE February 2026 Finally, we would like to thank Russ Housley and Brendan Moran for their contributions to the draft as co-authors of initial versions. Appendix B. Acknowledgements We would like to thank John Mattsson, Mike Prorock, Michael Richardson, Thomas Fossati, and Göran Selander for their contributions to the specification. Appendix C. Testvectors The testvectors use the following input: * Plaintext: "hpke test payload" * AAD: "external-aad" * Info: "external-info" * HPKE AAD: "external-hpke-aad" AAD is the COSE Enc_structure.external_aad. It is used as AAD for the COSE AEAD in Encrypt0/Encrypt (Layer 0). HPKE AAD is the HPKE AAD for CEK wrap/unwrap in Key Encryption (Layer 1). It is only passed to the HPKE Seal/Open of the CEK. =============== NOTE: '\' line wrapping per RFC 8792 ================ HPKE-0-KE COSE_Key:: \ a70102024d626f622d68706b655f305f6b6503182e200121582064ea61f745f7deed\ 186d697a4c89715932755017766348b0443a60aac450b5a622582088f53a4cbbcfcc\ 1bf0b33d5dc60f789a7f495244f57c158a8ceed5179639152b235820e8de39325f3c\ 0be02442076c470a46bca742de9bc2be453ec1dc049dda1f6ca3 HPKE-0-KE with default aad, default info, default hpke aad Ciphertext: \ d8608443a10101a105507af5398f1827c014f68bdb9fe84152eb5821d25b7b5eb83d\ c30f3a4d9ddadd9bd2726e88c621182d88ff53b39c5688c558f732818353a201182e\ 044d626f622d68706b655f305f6b65a1235841040189cdaf807a039007db9e298471\ 7cff68554f1bbe372d73a7af89cad1b3b1ecdcfca75e2c3786ac3a7f61bf303395e2\ 768b114ded2f4be39d40fff7917bb987582011a6de6b6c1e5240a1035c1239c7a8b3\ 000e7dc383818a97099f19b6c2b73b1b HPKE-0-KE with default aad, default info, external hpke aad Tschofenig, et al. Expires 6 August 2026 [Page 27] Internet-Draft COSE HPKE February 2026 Ciphertext: \ d8608443a10101a10550d68d7921fc2bf04d033edc091c7045f2582167788960ecb8\ 6bc44a71b67d4fffabaa94c032e7b7f639cd28574b9080b817e324818353a201182e\ 044d626f622d68706b655f305f6b65a123584104c73249f22b8c4171fecb3bd1093d\ 3c6a1288aab904db50cb7c688a5dcb02ef22fc734d6091472016fe087bd0eaa71694\ 821314321c6d193d842c220c7f58d819582075ea467d773d97db62deb5fd1507607e\ e7ca47e467cedcd79f16a4072678713a HPKE-0-KE with external aad, default info, default hpke aad Ciphertext: \ d8608443a10101a105506a6c63e17b739c728d65b66d39e85174582118b37ca471a5\ 306ba4745b9578e6a8cf618bc01d7f4f9f16c28049dcb12027677d818353a201182e\ 044d626f622d68706b655f305f6b65a1235841048115885e297b224f955c5ee9344c\ 944801e8633e9305763125bd0739656f6f0495af6bccb2c1e34d06ae586b186bdb61\ 8913e718456be702c2c84196ffee06245820e62641de898fa0534bfbaa671949554f\ 6d9db266270b0cdd8b53ff4255353a1b HPKE-0-KE with external aad, default info, external hpke aad Ciphertext: \ d8608443a10101a10550f07d00afe300fe71beb752cadca5bb245821beed09dcab8c\ 16c6ac26ddf5df3d47c6638467cb231ba934882499db30a5073d7b818353a201182e\ 044d626f622d68706b655f305f6b65a123584104b1d54393905a8551df3a675032b5\ 97ce40fa18dee7a4b11fe0ca93524e4f20cd6de652360acc99e72f8b620039d33a9a\ 1bdd542158a1a16b6d152264ddb701f95820602d1e4fac1cd619fd5f54bd625dd186\ 1d80ddf6f4e220922616a05cc86018cc HPKE-0-KE with default aad, external info, default hpke aad Ciphertext: \ d8608443a10101a1055089035dbd98078aac856737fc9ce06eba58210c356b57b017\ 0d371bf2cfc4c5d648164036726f33498ff2c99b1cee42257a197a818353a201182e\ 044d626f622d68706b655f305f6b65a1235841047ef0f70acf119a83c24b967af181\ 514fae47996bd0eafb4d8641e967802f28d58940fcfb4d28b4df4745a30700036b3b\ ccc2ced18c1375865f421e583fb0a77958202f93933dd09fb3db2cd287b738664d34\ bc263c89fab8aa6d46fa1d431814cd5f HPKE-0-KE with default aad, external info, external hpke aad Ciphertext: \ d8608443a10101a10550edb91df2666a50b438779cbcd25ab4b158212b48ca390e8e\ 5903e467390347a8f4da0710ae6c66d90693083d8d62265b72fd5a818353a201182e\ 044d626f622d68706b655f305f6b65a1235841041fb11d2984ca125db16fd99fd8c3\ Tschofenig, et al. Expires 6 August 2026 [Page 28] Internet-Draft COSE HPKE February 2026 f64862daee939a212fc68ddd275ee75b5c25a4b71c73d9620951d9897410c2a9f2f1\ 9aa5932446ac9b36b0ae1e913fe7bcc458200eec5d2195d413e32a60b593008a85a0\ cc1ae74c63823feadd35eca3aba3786b HPKE-0-KE with external aad, external info, default hpke aad Ciphertext: \ d8608443a10101a105509ab67637694ffe1f4420ededf9a3e4ed582110b9cfa11046\ c75524433a693b8bcafea8522939afa042519495e46e1c40996869818353a201182e\ 044d626f622d68706b655f305f6b65a123584104ae1c16e230410ce4f385288a7d83\ ebd0d12fa6760362e98c2c42dde16f8caaea74971025d8b39bae72a127fd795068d7\ f3447a282d37295609e9b60dfa1a672958207ddfc787b9372d6ec0215a8504765947\ 271074e6e81c48e2c6d5de95ac306526 HPKE-0-KE with external aad, external info, external hpke aad Ciphertext: \ d8608443a10101a1055012c4d08a6cb6da8dff2c072a152858875821064264f2652b\ 166a88373bd9cedd96d38cb65c650726578910ae6e6e6313258f94818353a201182e\ 044d626f622d68706b655f305f6b65a1235841043bf1b7f2d106d364416c27f3d7cc\ d03c3d803b9bd473c521456c51f8c1a37b917584b861c100c42eb0eb048519bc10d6\ 75ac8013174e669af6bed0f814cb614e58205c9e7e8f86b7ef1ba9f94425c9b0d8a7\ f43fc56df49da6b414629c2b7c96f489 HPKE-1-KE COSE_Key:: \ a70102024d626f622d68706b655f315f6b6503182f200221583003fcd256d1fd79ce\ 8d6d29e3cb72a823380e1c655aa2ce211721245873bacb76eacd6e28f4557fed2552\ 46a76fdd61b82258304dd4aa71088792b44e00970c2f269c1eb546e848a6df2946e4\ 409777deb6d7b77803a383c9e87757cef9f18910a1f76423583035172a2ccec0f1d1\ af547b811754e01de5406257ca808f2fabcbca5cbf7a4d22b951fc1d4da0e89e8608\ fde30d2f6706 HPKE-1-KE with default aad, default info, default hpke aad Ciphertext: \ d8608443a10103a1055820aac05a4dcbdd92e82befd10b4724ef077579404dd106c4\ bc33c69cb549cac1ed58214597a425b09b4ab5f169143378a5ff92169be65260098c\ 5ae834659444d753f672818353a201182f044d626f622d68706b655f315f6b65a123\ 586104bc7ed2fa3f73a546de2bae35fee30c39cad00e7883f85f2670a9eceb547262\ dfb8f676f701b7143a6ff693380b397c23572dd677fc7bd6a5de005662ef9f8a3c33\ 5c81b69b59fa585a70e449ae581421ead6f7a0a6d9c05e9fdcac0db1f60605583008\ e7f0466569e452d0f3e45aa99aa9dddeb04de6398fd55100578046c27e15ba13fd2c\ abc5a33202ecd547a4c7b0c99e Tschofenig, et al. Expires 6 August 2026 [Page 29] Internet-Draft COSE HPKE February 2026 HPKE-1-KE with default aad, default info, external hpke aad Ciphertext: \ d8608443a10103a1055820c8ee79fb915867c74d950d05f6ca9d43d47f714936684c\ a7f0254d7df92ba68f5821e74e07295b12fc4a8e518c5cff4d05df0bcfe55d29804c\ 6eaf2a176ddec72249f4818353a201182f044d626f622d68706b655f315f6b65a123\ 58610463a670ebf1628d5a6238c131aa98bee619c1d007aa703e3312eff22c2145a9\ 1f0dcb1e4787082e81720649780786e409fb9be9b7589d9d78e1d735cf1c664d4721\ 4bc1d4dfd06216c07a8ada1b3fe0f41fb759965d65755dd59e74247561b19a583021\ 15a5dcd6d165a7b30736723a4da24df149a89c0decde47e554abfc995b55a3eb89dd\ 52d5059b96449ccd243fd93665 HPKE-1-KE with external aad, default info, default hpke aad Ciphertext: \ d8608443a10103a1055820ac71a5659fe597a604fcc77a3d5b2b52bcd0d7d00fc5e1\ 57caf21ea9666a1f685821052f34eacd31e88626a199ac533fd0308b74268a3cd320\ df3e8697e5cc9ec6d211818353a201182f044d626f622d68706b655f315f6b65a123\ 586104639aaa2fe678c4186e9578c16dc72d6006ca8f7df7946b67843d7c4248da84\ d6a8ebb0f58fb84689c54b1f23c8390b41e77d4bc4c93159ebc3a7810316ce505544\ ac2d81309fb45eb64a3401558921e37cd861aeaf895e9606b066be1a609bea5830bb\ 266370fdb5c56669e4c88c86329ea9a84dde052c9482e4c6b305945d7c27e081b1d7\ cd5cd39c65ad4a4bd4bbeee875 HPKE-1-KE with external aad, default info, external hpke aad Ciphertext: \ d8608443a10103a1055820172e4e1b4df69bb472d261bfb43c78433c330625eae7f4\ a4e31cf10b2ceeb94d5821ebfa1a3352ed030fc5fef08ae1c1066bc7d9108fd45def\ 05396a6b4cd3401af48d818353a201182f044d626f622d68706b655f315f6b65a123\ 586104a355c7e5fa4a166ff68825bf094e81b9744aa2518ce381721c329952f26bbd\ de60f5fbde96fa47258684bd7277e545d3320b367ca06f42a56f6cf0afaaf1cb8ea9\ 6e4fa46b9db1dca72fd19988d9af9234d2b02a251eee800fcc03c260fa23205830d5\ f92ee2d4eff9323732c0fa70a071fa068c1572188b67ce1401657ff32c1cf4d3bcb7\ 0d2144ba4cfc323e4f93d8b8bf HPKE-1-KE with default aad, external info, default hpke aad Ciphertext: \ d8608443a10103a1055820393f4c0886145f63d4de2012757a496b46f80da705c4fc\ 7f045618b2b1bbe74d5821a580ae1f89bd1b84e546d94628c97c3548118e74c5026e\ ec543442b0bdf92f1d01818353a201182f044d626f622d68706b655f315f6b65a123\ 58610483ad6cd4932f0fc73a7e0640b5db583082b0d741b64a948404adc5624e67e9\ 167e9d81fd8d98e47afc006c2a366ff8f1c4062565c8b1e9a2cfe791120addfa86ef\ 6b444e957982a3f194fa2e932f6987b8ebf674b8a96d5ebdde8a4edcd1fefd583088\ Tschofenig, et al. Expires 6 August 2026 [Page 30] Internet-Draft COSE HPKE February 2026 f136f57fa98c10df0b8a09d1ed6833a25e197ee653652f104265e20acf723bb2ff7d\ aefc9db56f2120186c1d991978 HPKE-1-KE with default aad, external info, external hpke aad Ciphertext: \ d8608443a10103a105582086dbfa77caffcdcbc96b45ba891dd2b61a88ad0940ce5f\ dadf44526eb3b043ac5821a558899a7bc196b4b252f5cbf13a6d1ab2b45a083719ae\ 0bcd3ac3cf16a45f911a818353a201182f044d626f622d68706b655f315f6b65a123\ 5861045cd0a1afae98177f0f2fc52d75eb0acc5b4b8464ef7f14e8b0d90410f88449\ 6f21747e0b589b1fba09b0da8312476cfa7492e4dff1258128b9be4cf6d8e94e9725\ 75935075767d186029a34d19115d4fd908565389ecfd21a4a528eeecb1a704583095\ 8ff6ee18bd7aca20198ba18b220658c1db5c67a2251600c1eb698fd85812c271a5ec\ 61be430a8c985c9d0922815e3a HPKE-1-KE with external aad, external info, default hpke aad Ciphertext: \ d8608443a10103a1055820d19b7e6c324f92b83ee77477d5a646cd88b986b8c6f83c\ dec36c7d4892f7ba7958212d06813db517713f343ff5125ef2ac14c41b574b931cce\ 50bd48b4ed3e2c5dc8e8818353a201182f044d626f622d68706b655f315f6b65a123\ 58610499890247ae97c42ff00408e71396e17ff114ac35f35849da6452c1cab3cc78\ 186a65bfbf7a7c79e12c78f7c562af7ab5c06ac4066f175c49d5992efab2c521c5d2\ 90549caee7d175e32d3f9bf1212b438c61eb8a010ea5956ff51d207d197fbb583064\ b27d50df0f0305c139c7545bb339b4341c099d40294b55fe31ffd10d53ea9c6a58ad\ a98a89b5b7a2419434df7e6f16 HPKE-1-KE with external aad, external info, external hpke aad Ciphertext: \ d8608443a10103a10558209f03b841a61b17bf41e3afb0109933abc9750cf9a5f6d6\ 90a96283c9a8b30cf05821613a6eda5df30ef01a9d5974dd0f28598f587803a0e644\ cf22f5b78e42f38a9259818353a201182f044d626f622d68706b655f315f6b65a123\ 586104f85e706f0b1469fcc2bad6a25cb801418954d78344bf56e855e4d0241dc654\ d4050e224480e99644949875243cdb0cce4ab352e6e9ff3106fec195fa4bebe994da\ 650208b34b55b2f6a433609d6343d43e5a8abe8db28dc06f665cdef59984a15830a8\ 17dd751be11ed8596225bed31887383299ee632cbe319443a2b6f3bab515884c423e\ 0af2a29e7db0ee13daad9d69f8 HPKE-2-KE COSE_Key:: \ a70102024d626f622d68706b655f325f6b6503183020032158420033db899e500ac6\ f1fb7a9e23f16a363e41b6d1f6dd5562c4faaa0491f1a74cbdbd039ff2b5824842d4\ da26c36173bc31ba2d1672699d871fdca27b9af0020bb580225842012ecb4d569869\ 085618ce0a4e0f82fe9b618dae8b678e26e7a1ed8d8b9bdf7ffcd32dfdee1bd85ee5\ Tschofenig, et al. Expires 6 August 2026 [Page 31] Internet-Draft COSE HPKE February 2026 2097866c4f493a3174e6abb6b365057d212ce3d84a5010a6df235842019f28872f68\ 9d9c3a8018712e453a23beac37cb86c87e2c5a99d7e3901f2e4f4995fae274ca0774\ 8a7076d0ecae6466a7c3cdbc55d233544a59d22d3e4dde1d4b5f HPKE-2-KE with default aad, default info, default hpke aad Ciphertext: \ d8608443a10103a105582036694bc81347438c501dc55add947708ba52ce8bb52aa7\ b2878d26a0b9878d855821e6032422deb9c62db49d50c0011197c39b586660b7a018\ 443f1ab285f707019f69818353a2011830044d626f622d68706b655f325f6b65a123\ 58850400d55b883bb4f6f54cb0f147826fb706f01ccb19d67a8df4ce4bdf451f39ae\ 2c4e77370558c529c2022dd39e07f36e315705cafe57249ac9abd1fe0fd821a366bc\ e6013a2b390c1d3bf50f47cf19df06ee0564716dbc589c325a46fb66526167710a82\ a4e40c55629fb48619dde005fa002b994b240ab481c37aa4170f7d38c61674eee958\ 30933543fd556de228367ef1d4b1b6407461bd4a7acede97d25ebf67590078cc3fe4\ 9408300ed29d23be1c27b2902317a8 HPKE-2-KE with default aad, default info, external hpke aad Ciphertext: \ d8608443a10103a10558201d84edbb7cdff030f465bfce04a1e69e888bb092d660fc\ 7837754591aef06e4158218fdcf224296ba502062f6029071f5f120ce2f8f3ba20e8\ 1052a9e34dbda21026ec818353a2011830044d626f622d68706b655f325f6b65a123\ 58850400c2d331ea52e37a71ca3b32abf85f25ef92ac398c806de067fa344a97b111\ f00677a62ed2eac2d540e5685279ec03ee69a6b23ed78baf8229b7aa83d76318d86b\ 7a0142ad7baf09f065fafa8c887a5151272fd219d9c0b7caebf4f4e1532e261b5df4\ e5ce1b6ccb5dbfd86f5a6d7f0c34eb7f2da17b89831ebbf56791d18fb305c0197f58\ 3076cf3e4a3ff03606752d6b7e09806c02aa35a4677452bfd0dbd1a8abb9de682978\ a6d0ae2be5685d4ca48c85b5b2c0e4 HPKE-2-KE with external aad, default info, default hpke aad Ciphertext: \ d8608443a10103a1055820ef1d313af4d977ec69da4dec5fb387920fb5f0e1843dab\ 998a24ee94aa47a119582186a225225aadeed9ed918e6d1f48c4697e10a07085aa6f\ cbc0fdff18189b85f361818353a2011830044d626f622d68706b655f325f6b65a123\ 588504004074fd0f72b7237966abf252c0e41a21c5566e0f8c94c2a86c6d21e16035\ c57a887e5f69a3adf44a1580992bac716f2693a8fd3771043b022d016771b0498569\ 390168f4cd133158b2da000169f8676e3499161f35be790f7c26bd984b339b00ce50\ 5c18b3470f0e159741d63a1fe106eb1ecb6ca50c8130670f28c97bfc625ff33eaf58\ 30935ea79f6e36fd6785bcdbcdcfc737f01400d1262aadf8f2814a123cbd5a498550\ f3f30978aad8c71b5dec58238e9d61 HPKE-2-KE with external aad, default info, external hpke aad Tschofenig, et al. Expires 6 August 2026 [Page 32] Internet-Draft COSE HPKE February 2026 Ciphertext: \ d8608443a10103a105582050ffa1a4eddc067fa06db21366dc53f4746d1d7b4f9fdb\ 9e02532c80591e621258217c27fb226998f944de516cd7a13509aed1070e72bd4639\ f955efe6626a202ec97f818353a2011830044d626f622d68706b655f325f6b65a123\ 588504004a73a294d7a1c96685a9ca89dd657afddb2fd8263474d5d020d46a59ed66\ 290770b6e7989c60f800eeef64de8f823c9e40c99b5deee652b5c5d450b9ea127dc0\ 06009e49e147db35cae26ab891572765c4fc588962d0f71c046c3f7f627f09a41e9e\ 682d0d1740720ee8b73adb777c44fdcf4c343b08aaf01849c32ae4cdaa56e04a8958\ 30609a822ab35ac0e183c1049d0e80556d443c8a6f80a27da55f8c34605c240b720d\ beafe4961fd95eac09dafa4c090de0 HPKE-2-KE with default aad, external info, default hpke aad Ciphertext: \ d8608443a10103a10558208abd74a6f6494dca72c2dbdbd5f7771a508fb43adf7772\ 08e7dc828a9ccf024d582133db1cbe20bb05829a6f1a2d4bdad78d4b3c9e10dd9d3d\ e106454fbd6b967361ee818353a2011830044d626f622d68706b655f325f6b65a123\ 588504012af1fa72a02b73aa86229266d417f82dc19c55ff550f122e354dc3c7866a\ ef669f26cf2b57f9b9d3f373903dd1d0ef0c5189d41aa7cbfd4bfc4c955e5727420b\ 980076484702ecfbf448298ffa72d1d31f36d9dfd629104e5bd5f226c6fb992fa754\ 51d0114144b1908e93a3d5c5db83064bf973c9ae2f7876b669a55e49a3dc9bab2158\ 3040424efb8c1c3827fe491bc7e426dff929402372dcb44e5b29103ab7254204367d\ 72f56df75003b07fe4294b93fdc2a6 HPKE-2-KE with default aad, external info, external hpke aad Ciphertext: \ d8608443a10103a10558203099a01f838a003fc9119ee15835749011e099d23026f1\ 34a96b0ec2a99711005821aa17b650a15695339c627f95080f37b0e27bdd56d75863\ 6cedf5ffa1028490f407818353a2011830044d626f622d68706b655f325f6b65a123\ 588504015b3422b8aa732b57dba50e817eacef848ac0f6f9d41fe2496512442044cf\ 5cea24778deff337c76b26fe23f7f3820d95e22766d72e2ddfc54750c6c1089b585e\ 250043c612eeaf05c49b1df18066f8b4925d287c3b36b6177206b8964bcb9d2aab62\ c77117444ccb4164c7e60e07df0a00ccd28f19747c3d1b4999055a215e06dd0efc58\ 3046501065f28c600ff9872eadec2c958d4435edbf3c6aef7fe8b01b6b7fe625e53e\ 0186a9d52b26573031b49009ae1808 HPKE-2-KE with external aad, external info, default hpke aad Ciphertext: \ d8608443a10103a1055820d6571aef69ca1d95c29f8e32138f3b4cf73d6de02bd42f\ 21c5c245dd1281e95d5821aaeb110acefa649d60730cdf59fdfbfe99d4cd468f0af7\ 9912a996d6fc62946107818353a2011830044d626f622d68706b655f325f6b65a123\ 58850401a18bb1ccfe76360447ac01c17cfef513f41ab8a9d621aac0c3f1cd523fc1\ 5748ba0aa4526745260f918826fac568c9c1788db3ef20cabcb60d057ec4d01f7146\ Tschofenig, et al. Expires 6 August 2026 [Page 33] Internet-Draft COSE HPKE February 2026 cd005e52a1743fce60440f6a7e630165bee4bd7059ea01781488bf397416920d33f5\ 5f1cf0d01c89a90611c5a5a07cf493d693b02266d743a972652ca94e8652fa52ef58\ 3011f8320f59b91a8aee140d2edf61e0da9db310e42759577c3254f927b7d83d85d2\ 632a955ab4e1bb2c5093b37a8ea138 HPKE-2-KE with external aad, external info, external hpke aad Ciphertext: \ d8608443a10103a1055820ebd94a697400c2eb88607a0bc538915e63f5fdbe4f528a\ 11e559244b773da7115821af4eb2942d7596739651bb60b4de3c456cf74296af3cf0\ 665de158cfaabba1b188818353a2011830044d626f622d68706b655f325f6b65a123\ 58850401db35d812f17987c11a82fcc40bb40c540a7ace9c35b4da9b65dc03ef67e2\ 199b066a3ce082f9da9f596b73daf89b643756f8e29df45d0b78b002ba1d96f2661b\ 78005472f944fd1172c93c04df2e8a6452ddf5ba4c932d17604b58591903de3f60c2\ 8557a781269ce31779c1f2d752ec1fe9fc6ffdcdb6f21a71e6ae5969d07fffc0fe58\ 30d96f3bf5629c8c9cf315cac23cdf75c72c013df31434f9999eb2852111faa0d3c3\ 6c5e7f1b5ebd81b0644c38ee8e3bec HPKE-3-KE COSE_Key:: \ a60101024d626f622d68706b655f335f6b6503183120042158202d925acfd0ee359a\ 68565b619165985a7108f7b1771131e26f11d24177dc9a3c23582060cb9ff63744ac\ dac02a48527dfc2810fc49bc1223a240d870fa2d668c891155 HPKE-3-KE with default aad, default info, default hpke aad Ciphertext: \ d8608443a10101a1055057c9f2b6225deca6982d8f501953628a582168e4b863ae09\ e0179dfe7368d92c0e998ba891791004ac55f05b81fca899dcb975818353a2011831\ 044d626f622d68706b655f335f6b65a123582071075e8a1b304ef9edbc2936f6e5be\ 4ac2e4e7ad59ad37d748fb580bb5fc5c5858205b3704e4c7fd8f05c51fde7f159e70\ 1aeba21c55b82dec0e42b9bf9a6a9634c4 HPKE-3-KE with default aad, default info, external hpke aad Ciphertext: \ d8608443a10101a10550320b164a39702b84ad08f8e9b741445658210a1cda2aa5fa\ b6fde7026ef7fbef3faab763d7e3ef2b06aa09ca08b4de09a15d84818353a2011831\ 044d626f622d68706b655f335f6b65a12358209e0d94bb2d354bd6a83b9374d9984b\ e125bde4ae96230eff1d10d0254e96a97d5820b3aee0a1d634043403d61ba332ddf8\ fa899430e0221ba127eec76399a026a359 HPKE-3-KE with external aad, default info, default hpke aad Tschofenig, et al. Expires 6 August 2026 [Page 34] Internet-Draft COSE HPKE February 2026 Ciphertext: \ d8608443a10101a105508c0eca59bd53bffe5ef3b539c4ea5d6b5821e60895c561cf\ c588bbd124dbdab7bd2a19590f93e712f6bb3f745c6c8912366ce2818353a2011831\ 044d626f622d68706b655f335f6b65a1235820a141613c5ce54168fc1b9d76a4a28b\ 6461c8b65a14220086c3da2704ca0406695820bdd73f84ffb4d11d4d92391dbb34fa\ 8db2ee4f81299203f529f98ce52e49de86 HPKE-3-KE with external aad, default info, external hpke aad Ciphertext: \ d8608443a10101a105502ff672957f5586fd4a08d0fb045c6639582122758f93e861\ 925e3e40dab68a550046043c0b6183690696116b93093888e52ed1818353a2011831\ 044d626f622d68706b655f335f6b65a1235820a95c290e4366159abd514194334177\ 5f58521efc1ab15015bd368f10bbd5a53f5820c540b2af48b165f272a72d3a133846\ d6915627cbf3a37db34a312cd86cb5a9f7 HPKE-3-KE with default aad, external info, default hpke aad Ciphertext: \ d8608443a10101a105503a42e93d02472760b51fb62b464b4b9a5821ac8e71b022b2\ 4b2288579ef0c1c854afd28b74e9e784fa5d2f1528c477a0c90740818353a2011831\ 044d626f622d68706b655f335f6b65a12358203c9268ad53ea237b648a1806d667a4\ 5f74dcb725c7777fc558d4566cdeaadf605820dd50847d57ba2906c45b3365153bf9\ 3cad6dc9dc049fca46d91ac07a5354c069 HPKE-3-KE with default aad, external info, external hpke aad Ciphertext: \ d8608443a10101a10550dc32f24a9fcb7dd8da12372b7ccdf3505821ad11bf317640\ a6c1051ac0453ef9994a9a8a21dc34f2bb8ad17ac17bd902dc420c818353a2011831\ 044d626f622d68706b655f335f6b65a1235820bbca5f776f840f0c4eb5f1994c9989\ 2fd595f9df6e45787550a1624d3a3468255820140a9c10b359b476982d18f7f0fe38\ 63845501a020fc311b8a8a513df115acd6 HPKE-3-KE with external aad, external info, default hpke aad Ciphertext: \ d8608443a10101a10550b224ec850a723d60cd6fade231f03a7058210e151c37f85b\ ff7b382fd4158339d10bc1746a7d26dccf21d37e122f45456641a0818353a2011831\ 044d626f622d68706b655f335f6b65a123582056e5dc366ead34698fc0b4071a7406\ c6910beb1e8292b3dd9436ae34b653a0055820edd2498d3dae8e148360ea18f07d59\ e0adb4d283519d9d4b3820c9148f5bcd5f Tschofenig, et al. Expires 6 August 2026 [Page 35] Internet-Draft COSE HPKE February 2026 HPKE-3-KE with external aad, external info, external hpke aad Ciphertext: \ d8608443a10101a1055062670829c5fc6f5cdc48faab828dc09e58211ed421e07f98\ eca98f1155790c790e6710a53484310a47f3b7afdbc77b5a7cb5a4818353a2011831\ 044d626f622d68706b655f335f6b65a12358204370a8614e9d71a82998498493fedb\ d974def1ba2f3ff34feb5c8bbb1898484c58201e284bb8a5f35206429c5326036316\ a4c4dcd5772b7ed9dffdd1e3cfe02ad9fb HPKE-4-KE COSE_Key:: \ a60101024d626f622d68706b655f345f6b650318322004215820a5922a701eebdf66\ 5a7877e32b0651db5d3ad8eb4be792f2dfd9d9ac5d04956123582000f28ee18a4ddc\ dd4f318dd88ba71efe0bb68002015e9c4879e99edf4e9c4b60 HPKE-4-KE with default aad, default info, default hpke aad Ciphertext: \ d8608444a1011818a1054c06361aad32854c99401d9613582107f6ed7364a443fab2\ dc1710de081e8e535d621ab98d45e92cd15ecfac213dff6d818353a2011832044d62\ 6f622d68706b655f345f6b65a1235820ba1cbbf9ccacde066147b54ea4c28806c41a\ dd5495c37295d520d5332d247102583022d9d848d1e3603de56c4a3a0ece5ca75e6a\ 51b929d28142a53067f6169001da5320bbe23facb5c4f6f428f35c4af1cb HPKE-4-KE with default aad, default info, external hpke aad Ciphertext: \ d8608444a1011818a1054c9c4cbe7dc327ce468d50bd9e58216f145b2851c502d5b0\ c3ce4bcd99e96299e2aba606e2af70338c91b31c68a7613b818353a2011832044d62\ 6f622d68706b655f345f6b65a1235820e1e167e1917be9aa3090108e145a03d0fd20\ 4242800da4cab096573fb5f4f164583071397ad12d2a974dd23eaa363f40d3c59c6e\ 706b6b4c8d2a4ec4a6de92e860c30552336591bec0a8e51fe293bca83740 HPKE-4-KE with external aad, default info, default hpke aad Ciphertext: \ d8608444a1011818a1054c3d211831f229feb2b70db089582105a0acb03ea75dd18d\ 53bf05e648260c91c890355985a11d527eb8c4189590b08d818353a2011832044d62\ 6f622d68706b655f345f6b65a1235820c18fb4814d1f116b82836aeb213bd3528ae6\ a2417da08cc5abb6b15575217b345830ec408b0789d9097e9be5101e9e84a3076089\ 55570547964d2d840aecef45909361477ce85b012d4ad0d3bd9b2fad9101 HPKE-4-KE with external aad, default info, external hpke aad Tschofenig, et al. Expires 6 August 2026 [Page 36] Internet-Draft COSE HPKE February 2026 Ciphertext: \ d8608444a1011818a1054ca3a0a911408279f90ca90b0858214cbe2773a824c0e526\ c75dfd20285b2cef1d39605ff9b64e4f3e16ba943e237263818353a2011832044d62\ 6f622d68706b655f345f6b65a1235820e2d8f154d1a40c518058770f0f345b9d448b\ 418397ccc42d2af887ae9c137210583016932c4f4a574d2ab03dc02729dbaf404330\ a21df11e1ebc2e52c462e48fed0a0cd3219bff3e9eef5fdc19d92aad161c HPKE-4-KE with default aad, external info, default hpke aad Ciphertext: \ d8608444a1011818a1054cd7ab613f6cc110a022aaba5958210a1b3f842a6c339bc9\ 39bea0ec5a0f265777f67d8bb4b826252b6252ba4cdfc6db818353a2011832044d62\ 6f622d68706b655f345f6b65a1235820f8fec4f5ada1c6f6a6b1ee9b89092200c8a4\ 81daccfb51fd47b4fa99709427465830cd5b8342f3727d7afa5b981c7be6edeaada7\ 28833f801ec658cc77763d6de36af71122a250c5edf7df853c54dc486fe9 HPKE-4-KE with default aad, external info, external hpke aad Ciphertext: \ d8608444a1011818a1054cff6ec38f45005c1d36229a2858212291e110fe7cca10f0\ 258abfa31dbb9c8d019f88dc297f7a1641474650db40ec82818353a2011832044d62\ 6f622d68706b655f345f6b65a1235820e6fec434687bc3b5cd0597c4a56d76c325fb\ 8c21d4dfe8e7aaa47b4572c58f4a5830167720e484a884f32f961544bc2fa865cbbe\ e622c73bc98424871e7dcc9e7dbeb8b50edc8f6bd499a0e08b9bdb916841 HPKE-4-KE with external aad, external info, default hpke aad Ciphertext: \ d8608444a1011818a1054cbde082e4f5995e02d5ecfa6d582116efe45e6ac45104ad\ f41a3d46a627ad743f8178a0a326ddc1431d030172bcd35e818353a2011832044d62\ 6f622d68706b655f345f6b65a1235820a7252d0db32722de877846fefc59ceadd29e\ 698db423ebe3577cd6c0af195f675830520b088ea067725bfeb093abd31bb7516423\ 3a499171855f3d68cd93cad466d56fc29119c475b10e29a69951163383a1 HPKE-4-KE with external aad, external info, external hpke aad Ciphertext: \ d8608444a1011818a1054c2bf44cdd95f7de613426342c58210fee2d9d95bf69355f\ f885451849a0dad422dcb3cac652e11413bb87a16da8c333818353a2011832044d62\ 6f622d68706b655f345f6b65a123582063915e953e2d4a681251ae4e19fb61d4d059\ 1cb6cba32d989ec97d0d9c65841a5830c8fc0abec5ee853241c63be826b682119856\ d9dcc511a0aa4ae5121555afe61980716cd793312fa52ca130649e8b69f9 Tschofenig, et al. Expires 6 August 2026 [Page 37] Internet-Draft COSE HPKE February 2026 HPKE-5-KE COSE_Key:: \ a60101024d626f622d68706b655f355f6b6503183320052158384489c1479ccd3534\ 3a90b3e1cb4922f73d9d611f12bf4abe9f76fcac6a6a974c0941fa602dfc29fb5c52\ b3191ea896162718d2ddbc97097e235838785cb877d73f034edaaa14d66dc3e10bc2\ 8d3ee5a290310c89eab7e347a82218874963600cf36850a389325fcbb6e4477dcc0f\ 1b65e860d9 HPKE-5-KE with default aad, default info, default hpke aad Ciphertext: \ d8608443a10103a10558204ff93b1cf652bd6b3a78aa66aff3cf0763c4607fec098d\ 0ca74a6036f299ebb2582146d06eb19d65874a09970bcd52bca5d1ae70aef68302b9\ 5771ca57914b3100bcd4818353a2011833044d626f622d68706b655f355f6b65a123\ 58384099e311ea6ecb8c1bb579b3192634863e32c15374551b7cd76f38278cb25065\ 4fc7bd8d5d10d3bf020f5338fc89cb27b1be472ef2687617583092b0973eecebaefc\ 480ad5e606d6def1e78d22ee546831e49df7b91382b5d34e41e9262303525bbbe921\ afce1d3b4c25 HPKE-5-KE with default aad, default info, external hpke aad Ciphertext: \ d8608443a10103a1055820ee0407489df27075ea6c15d2c798ea0610e969b18d3d30\ 1867abfc60d14c571f582102485c143d33f60e3e3e6bf52e24a317991ef505085bee\ 6b593d85bfd763dc7593818353a2011833044d626f622d68706b655f355f6b65a123\ 58381e027e0f01b9ce80513f2945e81582922f593186a4ba6f015bea962a5856e321\ 00552f29a141e7ea288f379a2a3e6a6204ee5cbc37970c955830082a8b17e3e65548\ 20c31107b8b50d97caca42f6fde213a4c7494257d019e7d3bb00410301d3113d8114\ 6f64b1d649f7 HPKE-5-KE with external aad, default info, default hpke aad Ciphertext: \ d8608443a10103a1055820add0563a9487a69fd84c520c1b403ca469bfd31b3888a7\ badf1ace338489cc9e5821e5f53fb6e1baeb79c1e42bc88e414d25bb0deecb3fb75b\ 5e5ccc71a5c514b1b33c818353a2011833044d626f622d68706b655f355f6b65a123\ 5838a1cb8855ddead0ae82b4e87df4b399b7197b2f06d5ba0f4b053b104b760db9e9\ b2d53d924d403bb243cc2fa51d9d0eabf20150db69ad419b583014330834835b5951\ ee83fd58ebea9bb375ec5df0b373eec65c15a1f59ae7fddc8d16eaf11f67d98dcf4a\ b833b21e2669 HPKE-5-KE with external aad, default info, external hpke aad Ciphertext: \ d8608443a10103a10558204427ccf295f6163509a646b90fd9c40ed7a0fe9384cb10\ Tschofenig, et al. Expires 6 August 2026 [Page 38] Internet-Draft COSE HPKE February 2026 36a17b813b237524f2582103723c06533e16224e98d151063d708c7dc4c09b53b872\ 346c6083adee8b2fb43f818353a2011833044d626f622d68706b655f355f6b65a123\ 5838d6b7013b4c9f9b44ea55d9edaec03be7591cda435670066f3878c89ea5d49005\ f683d0dc1a8c85dddd9a79c8ff5993876b25dbc5e1231b275830ddafd2a0712a6845\ f11970adaf619f844eff75c8a381f80533c393fc5dc114b83a902c672af3d5390a4e\ 478ec6897ede HPKE-5-KE with default aad, external info, default hpke aad Ciphertext: \ d8608443a10103a10558208919fd6f31b0cbbdda4875af585af67e0c0823cef6d0be\ cd6802ea3ecef0c9a55821fb88175fd00fdda16def7f4110899c4f9017c63ec4b375\ 73f0dc4a97b6d9527b22818353a2011833044d626f622d68706b655f355f6b65a123\ 5838203f42bbdb8cfeb59f7c05a1580a885554f5ef8848c76a04a011b2b9521f08a4\ bf7d159b8f01762ab304ff57637400acc22d62746a942ffa5830ad7cb3c1c79711a1\ 1aff71f09a29228341485376d569fae65673c5a0ba0a4dbd5b7904ad2cea0ce1aa2d\ af37adc25e73 HPKE-5-KE with default aad, external info, external hpke aad Ciphertext: \ d8608443a10103a105582085aa9e38bdbf1f258426becc819a929c55e719cc75227b\ a515ae09a8267bf4925821f5d3bd70c82cdcd96595efbc671919c2698af5ef96667a\ b16894f6dd7ec5dc6a95818353a2011833044d626f622d68706b655f355f6b65a123\ 58384d97b5bc0f662d782b9122f113ca655d156674d3381b45f61a55f6f670771bba\ eff2187824469740f49ed0ec5bcebcf991851bd41fa95d5858306e0bd0c92cd5e4f6\ c74a34319a4738051e96cc3ddb69b6ef8dc0710918d02940c10688cd828b303b4b35\ 95d8bf2c0056 HPKE-5-KE with external aad, external info, default hpke aad Ciphertext: \ d8608443a10103a10558201806b9f94e356ed2f2c10b0822ff35b1504dba0b5a1db8\ af9b8e0d5c3792068058210a5eabd5d60b81eeff382c7598898e4fca0efcad5b27b3\ cdc05ae412b771495d4f818353a2011833044d626f622d68706b655f355f6b65a123\ 5838e3fbd237c85215a1d247176714e27f198a0f7a76e83f5116c97b218b5204c300\ 06dd08abf94892a44bf00a358f67822d3bf92d331b6430ba58307fd5803d162ea9ea\ adb8fc37b327d6b4a526a07ce4a13697195579ba6d7230f444568d1b731443f3bf6f\ f5d4f2c4e375 HPKE-5-KE with external aad, external info, external hpke aad Ciphertext: \ d8608443a10103a1055820de43c2aa8af6fcaf531231f6403cee6800fe1e3d0fc614\ Tschofenig, et al. Expires 6 August 2026 [Page 39] Internet-Draft COSE HPKE February 2026 7e090c1595fe8467ae5821f29e9f566935b3ef34e043891c935094dc1fe4984dd30a\ ac5877f98b0759055303818353a2011833044d626f622d68706b655f355f6b65a123\ 583803884f02e4d336a193959844a73db0b95f2511121886dc7bf82b945f8337c025\ 56efa96811b63cba029b13c60e9581a38366d6366177db4e5830eb8e0f189adaaf28\ 7119963680320da63ee1dc219982e7145cbef6437472b977344bdf141ceac4c4521b\ cd971c154ee1 HPKE-6-KE COSE_Key:: \ a60101024d626f622d68706b655f365f6b650318342005215838253b435291775cff\ 909b2227b8bd6f539f521368b33871022f95713b4433df21becfffeaba9d63e839e4\ 3413e92689ead254feae3d7aa8e72358382c6894f63ec5d05047370d9415d4c0cd53\ ee2633926596788a41b5ff5368733b7d9499c391b08ed7c1c3d750c4c5af2ff03a44\ 278c7c40b6 HPKE-6-KE with default aad, default info, default hpke aad Ciphertext: \ d8608444a1011818a1054cdc91705d85a0564634c28b9458210a72029b5ce3c44b85\ 28862f5f5764e438c7d723cd412bf65f681f7382b2084ecc818353a2011834044d62\ 6f622d68706b655f365f6b65a1235838e2d1ffe83d043f7fde6f14658e6ea3827e57\ 8bd060def6491ada7311a260c4b3f0734b97d3c3b8cd50c6f667df518c3d6a9d60c1\ d2563e8058300dc6bf0ce7314032e954f5eac21d5646b3d8a0f50a1beb3414da3e60\ 333d15b9edc7b8f9615bbb411b053268968b0be3 HPKE-6-KE with default aad, default info, external hpke aad Ciphertext: \ d8608444a1011818a1054c161f8d0c535147d452345f7b582105686a0762c213b2ab\ 775b71f5752e91a14ea742afc9be7d4dcef77408cbb3b474818353a2011834044d62\ 6f622d68706b655f365f6b65a1235838a06b9b5d98702887a49304d2cd174da29014\ 08c3a012cbc97c8548afd5e113a8fbbafa02df731f4f9ec314aacb389766defccbe5\ 087da31d5830395054dceb31dbac2381c37bf04f1db0f79b184482fba8f92a7ce31c\ b4fae7ebd9c4f52a1730ca3cb76695af047ff6cc HPKE-6-KE with external aad, default info, default hpke aad Ciphertext: \ d8608444a1011818a1054c2eaa13b8a25bf8e0971fbaaa5821abe79da1ef9aa997ec\ 00bcfbad70283b1c82874557c74f6d411742f0f35534c232818353a2011834044d62\ 6f622d68706b655f365f6b65a1235838c88eb6e1e4a8901cdda6340b0f6f0a22aef1\ eb93b8c9b0396e0390e4e11ceace150773c38614076b4a65890cfd87376117e92925\ 80ce9ba55830a1fc1274c68b001884bcc2c0bacfcd1c16ae3bd12366edf28da11adc\ ede0a5ba7b02550ac305f74e0c2e6993eb980617 Tschofenig, et al. Expires 6 August 2026 [Page 40] Internet-Draft COSE HPKE February 2026 HPKE-6-KE with external aad, default info, external hpke aad Ciphertext: \ d8608444a1011818a1054c777589e4029d40667c3f5113582178d2b8e3a9b4b7a676\ 0a5d442476370bb171134189415ce45957c2325ad5e6e8fa818353a2011834044d62\ 6f622d68706b655f365f6b65a123583805ab0e5f240b5a0add796adcf658a865eac3\ b661b19b45ec84d19d87eb4ce789f11e51a6641907d71a79a7e9e00372f8b03185a0\ aaafc23158303e0e1cf5cbe04cd7c99c804ab120374f4a53aa31cf867cdc6222e1c3\ 3329e271e2b10723e09c3e58e0d5440ff1674877 HPKE-6-KE with default aad, external info, default hpke aad Ciphertext: \ d8608444a1011818a1054c79c3898eee0f5d0c139ea9d1582122c443c0fb066dddd0\ 05678ab35d2409e37145f3a2c660212b307c567107d481e8818353a2011834044d62\ 6f622d68706b655f365f6b65a1235838c0d3df69fd572cc5b4ea701c50d3251b9aa2\ 8620a0885b9377b2287c52ac6a25381921c735c82f0d471ccf8eff4f7096336db9d7\ 6231c8fd5830152b3a5f3833c4aed2d9d5a8e15b782543dc84709ac4706379eee3e5\ e334b0b9f56aec8770765c7b26bde266af673208 HPKE-6-KE with default aad, external info, external hpke aad Ciphertext: \ d8608444a1011818a1054c342275d497bd01b56282649c58219cedf5c89b5f3e1bca\ d64725c0d90a2184eedd1e8b7138b80d8c0f5cc1abf89e33818353a2011834044d62\ 6f622d68706b655f365f6b65a12358386e741c2825336f78c666cc7ad296920b25c1\ 1b6d482b235ad243172ce301dcbcaee23a076beabc6c282f2ba757d50fec9c6af0d0\ 706d98275830e89f61c2fbdafb5573cfd12220dbd4545fa54b4d1412833db1b56ab4\ 84f486164138d9b84a2b16bdba3c7993ed8bd4a6 HPKE-6-KE with external aad, external info, default hpke aad Ciphertext: \ d8608444a1011818a1054ca9fa34a4e5f1846e9afeb0a258219e4b6d9512d4d4fde5\ c5ca94d3babd478132a1ba3f92448fd25dcd26a483c2cb25818353a2011834044d62\ 6f622d68706b655f365f6b65a1235838a23c08691c61200eb23cf535ba0f0252f7f0\ 09f9ce24f7df7ad71a974536a01ff52d2ba12345d74bf751fd5382166aed53b2a786\ 35d4aa7d5830691f2d587f1748e87ba11dc1c10dd7602712789e85eaf63990d36a00\ 5ceb9041c119c8629d0cb366a8aafe0473a56b4f HPKE-6-KE with external aad, external info, external hpke aad Ciphertext: \ d8608444a1011818a1054c226a8d618d7ce2f1a116e7a8582120c2989b87f908e508\ Tschofenig, et al. Expires 6 August 2026 [Page 41] Internet-Draft COSE HPKE February 2026 443d80c3c7d35c3860da0fdf77edd51846874e38153d9b43818353a2011834044d62\ 6f622d68706b655f365f6b65a1235838ae833f2ab29229c1fe66f025d30facde2e87\ 71940275f0b67934cad41822a7325ae9669f3cf8dc11c034c9105d67188a40d0343b\ ce70bcdd58301e78d4468b91719a6f1e6f6a2e98efa55f92a0713984e4fa677f44f3\ 9acacf65559af142b5216786588123e8fa3d73d8 HPKE-7-KE COSE_Key:: \ a70102024d626f622d68706b655f375f6b65031835200121582055137ef3179b4bba\ 4326a5e73ae0966d92d2ccc7e1714a66fba562a1c597a08d2258201daa17ff95d717\ 128dc944069f4060af5981575734f1f847e6bd6bc30603cd6123582073294f0f394f\ 08becf7358ea89c0cda596cbd9705a6b7c6f0ae8d70a9a85a913 HPKE-7-KE with default aad, default info, default hpke aad Ciphertext: \ d8608443a10103a1055820b4ad67bdb6937286a5983cc45f54b41e3c7a0df82e12f1\ b7e7925bde628eca6a582142b48f53df1fcc1caf84bc4820476082e55146a04e1726\ aabea65114de8329bda5818353a2011835044d626f622d68706b655f375f6b65a123\ 58410433c37c35e3c3c333aff1bc62edfa2765518c7cd4e025a8b23ffb3fcf78f13d\ 051cdb830d89f97e1567f27362420b63d0cbc4c1dcf6df18f2c599e763c575c3f058\ 3029ee7739a3699d79e1ffbb652f99741a1e2d15cc05bf68d8a9f55bf3b77e33c22f\ 5c7bdd3a842031325f385f6ed972c4 HPKE-7-KE with default aad, default info, external hpke aad Ciphertext: \ d8608443a10103a10558208123621364280f31244476af7ba86971aee01f51ec197f\ 63127acc2845c1c23e5821f71f66a19a63bf08eeae9cab07ab5c8454816f7370a6c4\ f58630647a5988d5b823818353a2011835044d626f622d68706b655f375f6b65a123\ 584104ba669a6cdf24f9eb902c0647fa7011c764d210f10c4de956188b2137829b73\ 6b1d0ec5e6d71ca286d279391a4d129ba3cd904edc3d61ee98cf45528b81e3f9db58\ 30b2e8ad669f478914862185c6ec6f70593d29b8e2ec523b7d89f9cd914ad34ca775\ 2fe3629b4680c8466942adf7a14ac2 HPKE-7-KE with external aad, default info, default hpke aad Ciphertext: \ d8608443a10103a105582073a819dcb519a63355b711e7ba4bd278a25a5065983b94\ 90f0169c3ca1a6c446582159ef651b16dd3eccb599906d27a3f3d06e09efeb0bae14\ 7f5cc3cd8ad876697401818353a2011835044d626f622d68706b655f375f6b65a123\ 5841044fd069ae9dc9a029979615eddba8e946dc4087817c8e02680dce2b0415fa88\ 39904afe73c3c045f32a010603ee158deb96e3c5a97c501fecf9b29b8914d4a71658\ 304c694a5e09eecc922621d3dfe02b7e5dd0ff7c174ad6001f24a0764867f8a3c18d\ ad15a51d85542ef85b0753f4654cee Tschofenig, et al. Expires 6 August 2026 [Page 42] Internet-Draft COSE HPKE February 2026 HPKE-7-KE with external aad, default info, external hpke aad Ciphertext: \ d8608443a10103a1055820bd1930d292a90e8c717057f53fa6bf9058e0b9d3e6c013\ c6e19061ad839a47cd58215bc9e46ef5be53dea520078ae2e41ccd5b9b5419f273b5\ dd8c35459184eb8a8512818353a2011835044d626f622d68706b655f375f6b65a123\ 58410438bd711f6e6cea92c0008fa4b6e6874d6466ed63ae3031a87ed03d074b236f\ 1b07526363c63f5d90ef5ee45a41e00f726f3bf1c61a0de461f1da41545f055c2558\ 30795f8c1b78115df8af58f49b8f5fd94df744f50f6f36836cd15441dceb88c196d0\ a4014ac8ed81832a6a106dc974591f HPKE-7-KE with default aad, external info, default hpke aad Ciphertext: \ d8608443a10103a1055820921ada478a6296b81674ec480e27ff77ef0cc691967b23\ 5920c45be58079f1fb5821bc50d6b7348a33fac2aff9d9b289dce83c8a60050309fb\ 6f432d564a6e6b909366818353a2011835044d626f622d68706b655f375f6b65a123\ 5841046d92481c24059c5d5ae998048868ac975a2d87136c62dd53fca5cce700f45c\ 2c7da093dbf84545880f8f81fd51b9d73622153324ffe35ff80ab9edc828b6db9458\ 30f6c919e08dc6f0dddb0bec457ceb6726f5a3c18d97389d96d894b553e602f0d484\ 49740735f900b1d6fd7e4003457ee8 HPKE-7-KE with default aad, external info, external hpke aad Ciphertext: \ d8608443a10103a105582003a092a86b3432027f1eff4e1cad509aa786f73a5148a1\ 7d0071b7798a5b2206582153bbf01e70aaec7dfddea48b28dd511afadc6edc7524bb\ e449ac677c2136c994a5818353a2011835044d626f622d68706b655f375f6b65a123\ 58410481bc8c8fd41e43207e76e38a808c04c69ac716e4e95d712732df1bfacaf548\ 039db70e5ec9374f6744eb88b8d4480de1caa03f6fb7a3c9ae7b60f7715e4bada858\ 309d22782eedf0f851fa507b74fd05d1bd7d995e15bbd5162ef0ab08840cda5b6b55\ a7ed79500990cefe94a8f312518bb0 HPKE-7-KE with external aad, external info, default hpke aad Ciphertext: \ d8608443a10103a10558208e23d1384869e09d81b29aca4a6c914f5b6e1fab762986\ 00146e7b82bcd3349558218784389faa384d51bb2488fa493d63f2e3fe72634c9994\ 4c5a8b7bb32e6ad4b5fa818353a2011835044d626f622d68706b655f375f6b65a123\ 5841041542669339ff82f8c64acb331de9103d339042bf8bd61d75056cd05d70d136\ c2b481b1dd2b220196228a1f4a8f70991176deb68ca4900a698878900cd3bf763958\ 30f611c9c31785c2d7bcca2638da2375131fe2287b72f4b4b93ba1d8424ba12fe6a4\ 8bb8ac5d0bad1cf7b8f81cf9d11bcc Tschofenig, et al. Expires 6 August 2026 [Page 43] Internet-Draft COSE HPKE February 2026 HPKE-7-KE with external aad, external info, external hpke aad Ciphertext: \ d8608443a10103a10558200014fd43c613aaa6578d3001abeef3c028cb1c3079f21f\ f6da777a9c586b985f5821333e109d32d4cb58224e3cc3958b0696233e4a824586fc\ 953056b55fb0f988f9e3818353a2011835044d626f622d68706b655f375f6b65a123\ 584104cfd2686a4ab624d792050d5fefd9f128467196fc437fccc02643ed770b1944\ 502d9515c98bad76e6b4c3c982ea8192124bc3dfd61901af0bd9676e5e189a93a158\ 30334cdf07561053063f668bb025f4d46cbab5202de419d34ce5e49290c886763b17\ 0fcc5586f9eec223a6a94ae484542c HPKE-0 COSE_Key: \ a70102024e626f622d68706b655f302d696e7403182320012158206699b067898b7d\ 2d37db0da3aecad4bdac1558870b47d67d080d6049fb81752f225820b01b6da1f210\ f46e20e2b552a80f4f6b9a3adad34a6701f73fbbeffb174cf7412358206716e93d65\ 94fbfd27016daada9ccc8e6ba2eea0e103e3d7ae22278f6dfe124a HPKE-0 Encrypt0 with default aad and default info Ciphertext: \ d08344a1011823a2044e626f622d68706b655f302d696e7423584104bb6385b1cd50\ 09597006380ba2de0f66d293007755640f57b13a234bbe7241cf6f91f45469f85e99\ a13b9567257b7025298bcf6e7f4c1f29ab5229381f4b99e65821ed584cb52cb37201\ 35d1aed21adeca560e00effb931cf17f9b60542abc92e80b63 HPKE-0 Encrypt0 with external aad and default info Ciphertext: \ d08344a1011823a2044e626f622d68706b655f302d696e74235841040c483c4a0f7e\ 41e98c585fdb19ab95789ec6f7f6fe3e7e4943e3e0ce147e42c0688808a3284f779b\ d374d2a83e72d0248e3c6339a932cabb35c084071b75670a58218c9fd85ac5f111b2\ ef077872bcf72a7222a8ed8bdcf6f4036f304eb03c75450067 HPKE-0 Encrypt0 with default aad and external info Ciphertext: \ d08344a1011823a2044e626f622d68706b655f302d696e74235841048ab08975a473\ b7e85a8796479a986b1d57270074ab819bbea2eb48a666c78fd4cfa1558f56dbde81\ 848b19b1a2bf9a8438dcf8e4a2d800bb155cbb6e9b41956e58217a8a794081022469\ dab987927fff8e642d7f2f44b96eab7bb5b78b8fe7b5e6f2a5 HPKE-0 Encrypt0 with external aad and external info Tschofenig, et al. Expires 6 August 2026 [Page 44] Internet-Draft COSE HPKE February 2026 Ciphertext: \ d08344a1011823a2044e626f622d68706b655f302d696e74235841049d1716049cee\ 3aa5f23d2b3bbc96fd251262a97d3b0dbc53eac742b8c89fe887af7ab816ca8aee7a\ bacacd1a2ab0495e57aeff22611139d1cf894a666529b1615821590565fd461c31ed\ bfb529c208c29b87c7c924b9c570d8308cb006f1c86b646544 HPKE-1 COSE_Key: \ a70102024e626f622d68706b655f312d696e7403182520022158308309a370b333f9\ 56c1cff9d94e1ef8aacc2808ca898fec0476d9c132893704a2a4ecc88bd002e2c713\ 83b97bb3ab65822258304b2a3e1b2fc832c136aee1632f967b31f5afd0a32c8c9766\ d0e9d0e4e2560a905278b0d9965898b3fe4d2165cfa1b1c0235830bde0361bbbf278\ ff3286a36897b2e674286870981ef471c2c81b55a3b82827800d32b34da68993cd59\ 0ff06e0788aeaf HPKE-1 Encrypt0 with default aad and default info Ciphertext: \ d08344a1011825a2044e626f622d68706b655f312d696e7423586104652d74d6ded6\ 32be58dfdf81aeb3e7f365f86ad170c509dac27c2107551538c5b4ea89f36b6aa431\ 5b39ec96528c7b0d049f5c70d801e6d522e7a91f559b52eb2b706d93f3f11d1cfbd1\ 906a5c4c3380150d46926c3f469526389ecd0e1f9db6582144c5fd46930ccf302b53\ 15faa3337d76c8622fe8ec6df824ad7e376007d52e02ac HPKE-1 Encrypt0 with external aad and default info Ciphertext: \ d08344a1011825a2044e626f622d68706b655f312d696e7423586104106388d784f2\ cdaab13c77b6f67d0229d552ce2e7707dc5a17ec01f74637d4275ad2a931ca7d0062\ f7bf45be096cc29b7b2ba96efc974ce673c29d47a7a2db63eb0a5c55aa6c5abf9f72\ 8f7b4f29435437c59409584a61cbcd4a83a1f876fe1c582174d9cbc04fd6fcc0ad6a\ a587a38f21be70e381f4b8de184c4e7e3fffa246418ac6 HPKE-1 Encrypt0 with default aad and external info Ciphertext: \ d08344a1011825a2044e626f622d68706b655f312d696e7423586104fdd2d7553bc3\ 1201851cacb28ec135df4ba6f4cbc92362a18d3024ba3944a74ff46bad3cedca9721\ 5c8e5c337aee23a04bf42d777fc2a38e14ffb0337a983de8e6fdc28714b527180733\ 33aa374bca263d1b270bb61098be1032271cf5e166fd5821124c3c9acc6700f6faab\ 0503ea8306ccafa6ad341e69017b5d57877bba7c8d7c4c HPKE-1 Encrypt0 with external aad and external info Tschofenig, et al. Expires 6 August 2026 [Page 45] Internet-Draft COSE HPKE February 2026 Ciphertext: \ d08344a1011825a2044e626f622d68706b655f312d696e74235861047a2c8b275dd4\ 8bba7666452c6ee4db7e4d9c53790344b446223753d4fd6c15b6a513cf223af09355\ 62820f9336396edd5a096498dd7c49cd7dab87a86cfa03ef507bdfc3de2403569cf0\ 2bd702afd76c756d9aae114ba4dc5b94ecd29f62d383582171c1a6219cf72d7446a5\ 9c00c5fa692d17c0efc3b92c34a2ff0cc56adcea9b65e7 HPKE-2 COSE_Key: \ a70102024e626f622d68706b655f322d696e740318272003215842003c20a6d2990d\ ac871dec57d8f31283ca99b9958a00e92ba43b1ff9186813f750b01333ef1f311960\ 1875065599aa48884425480a4d20e8e39bc84e98f745d91ed72258420058edb9dbcc\ ddc1594dc9003ab39886babd7ef7d0046aa72eae0f9c67b794c251c8a2309ae05f6f\ 1cf4ac06045ecd45bc335d5c316936e3968e6ed42211bfdaa859235842010c50be4e\ 0322d8bcb1424750f6ed3b22bcbe25ae9745a868688dcbbab97f522f5a95d0712b8d\ 9ff48a5be6650179fd4e59913c76b1b28af9605ddb294756c2effd HPKE-2 Encrypt0 with default aad and default info Ciphertext: \ d08344a1011827a2044e626f622d68706b655f322d696e7423588504009a6b229af0\ 1086f3d269bc53e80af50c51fa34d7919137f7ee341773859909eb8a42d528d3cb4a\ a8d11e2b0456a1eea80b77a5ac960c22899e96bcd5a41b57277101eb8043867d62f6\ 4de2c6400d5239b17d5fc1c1544eba22ee4c2f464fbb88a0b24d532b7587727cca8d\ 93f5a39997a3cb9ef2490ea1d1fe46a45fa96fb2b26bf6ec582199e3fd2ccf2add11\ cd4be8ea6819e00af7b3a37d46e674ab6028376ff99125ce2e HPKE-2 Encrypt0 with external aad and default info Ciphertext: \ d08344a1011827a2044e626f622d68706b655f322d696e7423588504008f1fbff7e1\ c3960d04ed74bdd86b19c995af96468008b7ad62e9ca2d060c222fda6bd30831e04f\ e797b6a87f7b0eb325a2b0b0e5331d302aaf69aa386ec9276fa901dc4056f6331d58\ 093273ed605c1e1e32b2e368afe71390246f8fa20d7ffc6e790a06d86e588f658bb0\ bee30c523101b351433ea1c611cd0d2fdf6e924fce55eed2582120bb19765d3444e4\ 3325d1c8a7d4a510c4a85a88cf3b9a2763e477f9e064e08510 HPKE-2 Encrypt0 with default aad and external info Ciphertext: \ d08344a1011827a2044e626f622d68706b655f322d696e7423588504006dba8c9caa\ d42c743aebca073875e1e5780c828162072850df9a8c83975f64dc4466152a8bbd12\ d7bef79c00a589a0b8bced83b8fa82fbc1a50a33e0a54a1420ae010b5dd6dcc9bd0b\ af5101485f37d011fdd902dad39843343bb57be244e566047a60d54a15ec9c8d25d9\ 1b97ea7be7a1ae118898ec8c273d88198ba4d0f5e74ec14b58218e160a01123c22b9\ Tschofenig, et al. Expires 6 August 2026 [Page 46] Internet-Draft COSE HPKE February 2026 a4f4859a9d101bdad6ce576c6cc68343ec54f32f644facdba2 HPKE-2 Encrypt0 with external aad and external info Ciphertext: \ d08344a1011827a2044e626f622d68706b655f322d696e74235885040100fffac417\ f1ddde4c2f9316e7031d73aeb7e21e2223da751c310971d8d78861fe437facaad58c\ 2a72abc8ffd5c9c052ce345c7dd7a871204f8d90669bc8a3679f016ef52865c7bc9a\ 221dc67c1a9c12405943772a7db4658c8855b80b6883812ba92017f8fb98bf9bad12\ ac14a7e2eaea2c7fb3a9513e117ccf69c3e6998abd0e3e2a5821657d17e9ca01ee51\ f7a88a870ac0719e2c1ae8d0881e6e9c03ffb4834d586aa98a HPKE-3 COSE_Key: \ a60101024e626f622d68706b655f332d696e74031829200421582085eb6351a4e93a\ 49953e1e23ade9504af68a73196a823c9a0654bf98c7536a7f235820f0b8ece6e393\ 8430f36798eeea8206d0ac5e0577349ad63843cbbb63bc90b849 HPKE-3 Encrypt0 with default aad and default info Ciphertext: \ d08344a1011829a2044e626f622d68706b655f332d696e742358200a97fc27b9542a\ 666479ad6635d9d5988e2bb187db4f8b3b48f60f2d06bac46b5821f058dcbad9bad8\ 553fd6cbccfd50486e33dd96557d5805c6327af6624760bc7a1b HPKE-3 Encrypt0 with external aad and default info Ciphertext: \ d08344a1011829a2044e626f622d68706b655f332d696e7423582093a055592c2978\ fe4c7424e649938700ead043668b0a12c4233350f7927a250958216ec61f83f6fab2\ 79d636bbc78bccaf9d06d34b9f39b0d615b26066c1c584fc05e4 HPKE-3 Encrypt0 with default aad and external info Ciphertext: \ d08344a1011829a2044e626f622d68706b655f332d696e74235820b9a5e203033c7c\ 5d15bce2c35cd59e24db38db2114b9c5d16edc5d7ec4cfb54f5821807a3046ee8c72\ 5701d5e9bf5472772e84b5a2cffbd4b296d55af264da8b14b87e HPKE-3 Encrypt0 with external aad and external info Ciphertext: \ d08344a1011829a2044e626f622d68706b655f332d696e742358201d6124b3462a25\ Tschofenig, et al. Expires 6 August 2026 [Page 47] Internet-Draft COSE HPKE February 2026 d3ed374b88a4702afa7831aafd81af5c8774eceef569f0234658210fcbc960c3f6a0\ 49cbff49d881fff00a86152cfbbeccdeec111fdadc848665b9f0 HPKE-4 COSE_Key: \ a60101024e626f622d68706b655f342d696e7403182a20042158200191a45e724023\ 3a4bda72ac8b38283aea336c863c7d5856b7df263038bc69072358200838e90c3407\ 649faf0bd7eeb3e5a9fd7c643e4cb72b91997fc81d26d2f1de49 HPKE-4 Encrypt0 with default aad and default info Ciphertext: \ d08344a101182aa2044e626f622d68706b655f342d696e7423582081cbeefeef0b8a\ 8b736f700fe52ff25f0cfc7302e5075a44b95e7cf5a82a96775821e5c0ebf3de1016\ b0fd33f41c0774d6b283dd494537c729ad7decab64bd5c1f43e5 HPKE-4 Encrypt0 with external aad and default info Ciphertext: \ d08344a101182aa2044e626f622d68706b655f342d696e742358204c41250100e5f5\ 05dd0acf8830ff1d22e7954d8f6d88d59c809c95d903849c4658218c99cbbe71f8f6\ 95e6e79dc6f412793c3ea9d1464066e2d08aaa27b5fef24ec144 HPKE-4 Encrypt0 with default aad and external info Ciphertext: \ d08344a101182aa2044e626f622d68706b655f342d696e7423582004aa6884ce80e1\ 88a0ef5496c24f6798afde8c8dc623bc2654ce836bb2b9be4158211bc91f4db16f81\ fdab012e74c00ae5353eb258e433b8ea4b28893d7436fe7615f2 HPKE-4 Encrypt0 with external aad and external info Ciphertext: \ d08344a101182aa2044e626f622d68706b655f342d696e74235820bcf1e847f43e3f\ 4244751ce5e4ac782fc5270310590a3cf8fb825e5ad6be54145821e9c1313608956f\ 65a12558a94ce3fa04ec84ecdeb2eed4eee2a4fbbe783cfcfdd7 HPKE-5 COSE_Key: \ a60101024e626f622d68706b655f352d696e7403182b2005215838fa09d4a5d1fa3a\ 7b2b6de43b08c715283d7425b80bf8b628b07d0d077283aa9c1507354e98c087688e\ 8cfe7220be5e2d44509b2fd53b24e9235838b07f1d8cb1d2f3d5ba62c0ad5a1791e0\ fe79f6fdb9f49910274aa184855b67850ab2a53b39b131d07bc3d4e80a4f83b1c9f8\ f5f97f1fa598 Tschofenig, et al. Expires 6 August 2026 [Page 48] Internet-Draft COSE HPKE February 2026 HPKE-5 Encrypt0 with default aad and default info Ciphertext: \ d08344a101182ba2044e626f622d68706b655f352d696e74235838a7887685085eef\ bcf8230ce60ab6d18c01044807413f38ef1203b73b8083d37c3474fe2e822945c77f\ a011a4c808f55fbed005c8e90a90e4582101dd9b944c4e051fa9214aa99296a83f81\ c04642f1f6aecd6f9304bbe5a92954f8 HPKE-5 Encrypt0 with external aad and default info Ciphertext: \ d08344a101182ba2044e626f622d68706b655f352d696e742358388cde9ba79de945\ 37b33e121f3c8d3c5a720c9d3e5eaad0f0e0f84e323d592d20afa87a09657765d5ea\ 57b27659366cfde26a80d817e5b6ed58213794aa4fbbc9807f953c23eed30e575d16\ e83b488a521b03a7e737ce9a6f7e90e4 HPKE-5 Encrypt0 with default aad and external info Ciphertext: \ d08344a101182ba2044e626f622d68706b655f352d696e74235838ca713a0271741c\ ac564ae35b5278b343ce9b3f0f2a5379a0f20f6f759b682ad9884926185e7f2fb9db\ a541bc2a41034392e430c3f429f16a58211b393d9ba77bf79efa231d87033cf8a407\ ba249891c098abf834b63e222aa744b3 HPKE-5 Encrypt0 with external aad and external info Ciphertext: \ d08344a101182ba2044e626f622d68706b655f352d696e742358388c4b45493d8b3a\ 5cd88bb3022e3e0a3777ac3b5f480e448b509089bb801608654a984e85200a70476f\ 206b0bdf045063a57f472d63c69b1a58212a35247d2dd06d3bcdf02f6d26e751420e\ a966907612e4431f44d7f792e91818a2 HPKE-6 COSE_Key: \ a60101024e626f622d68706b655f362d696e7403182c20052158380aff5f4a86fc46\ 8a25b7715d066628125dad13e4243f242cd6585f89f7371a55cfc3cf42cd3405a78d\ d380b4e9f4d47880c684deaa3f8aa923583898b6c98f0d48162ecc4c0f5e09c97246\ b03564a2672e12496f0f7a0d0576fbbdfb287b5a868e5b569a55b7d3765e5685feb7\ 270471b13392 HPKE-6 Encrypt0 with default aad and default info Ciphertext: \ d08344a101182ca2044e626f622d68706b655f362d696e74235838a17baa842458b4\ Tschofenig, et al. Expires 6 August 2026 [Page 49] Internet-Draft COSE HPKE February 2026 d082f042e5598e072bbe19b9970963ca0428a577add73c7a8d275e63f53971f4ba96\ bf842201d1c4776122dfffbc04e6cc582157e46f77fd6c2f2cab3d0810d67b7eac73\ 41c0726ebaf978a8fafda78f295fad0e HPKE-6 Encrypt0 with external aad and default info Ciphertext: \ d08344a101182ca2044e626f622d68706b655f362d696e7423583851e914d34210e5\ fe233283c2755b6a42cfb1ada1139d9ece7664e57336b03892bdc67cec396c13dae4\ 37801cca5c885901fb616a96166ce75821fb3979eea60600d09bb76b4f3a5596ad5b\ 194b21e713070fe7b0fa1443b809f65d HPKE-6 Encrypt0 with default aad and external info Ciphertext: \ d08344a101182ca2044e626f622d68706b655f362d696e7423583842ad024c1f764c\ bb797b3558d9c8ed9c3559c65870620c7b56f3367fdc65bc7b696d96411b57cd47a1\ 56fb945a939aca63f1a168f1a7d96a582197c449697f868ac6a708a8f9a1b1c32537\ 2edf6333c87e8d5f1853e8599a7848d2 HPKE-6 Encrypt0 with external aad and external info Ciphertext: \ d08344a101182ca2044e626f622d68706b655f362d696e742358380a100686fd1f04\ 0155a64da572a9e9109487a55c7fed63c68c7bb38311a7b9c48d1555e006f0db2884\ bb4306703a9c5cb7c4a0e4afd1297b582199c40b5fcba3fa474ebd9f44326e308b46\ 2a2171a5c50294329284f0e333ed5f15 HPKE-7 COSE_Key: \ a70102024e626f622d68706b655f372d696e7403182d2001215820df717fb8deae1b\ 58b754487c5432c8ec9a140dd11bcc7cd65cbe4b728e9263d6225820a8528d614367\ 3203144a9636ea065c60761390916f2218c8db958a64e263d3e02358202343a73ed3\ dc2b5e110d734c8d5e7a8b7fea63849e78a8db3da48a65ecdb720e HPKE-7 Encrypt0 with default aad and default info Ciphertext: \ d08344a101182da2044e626f622d68706b655f372d696e74235841040ae250a36575\ d60ebcd50444d99d1f1546438585fc807338d0a69cffad14d45b28047e5e4d7429f6\ 28e9f8313058535375dcf1ce1804a83b8745b2d63064cf6b5821847f648fbeb8e386\ 89248933366fe6929e36843d7855e318c48383f54022b7bac7 Tschofenig, et al. Expires 6 August 2026 [Page 50] Internet-Draft COSE HPKE February 2026 HPKE-7 Encrypt0 with external aad and default info Ciphertext: \ d08344a101182da2044e626f622d68706b655f372d696e74235841046a563d7eea74\ 4ccbacc9ea6df50e002d8b235fabc7023d51c75e5ba22af4102c1c20954d6cc1b2b6\ 3f893d504301c94fc37ba89084d04ca59f96581d87435f215821d619e5c0189533c3\ 9c353cab4db8a939225c170e840915b27503b9de88f5451beb HPKE-7 Encrypt0 with default aad and external info Ciphertext: \ d08344a101182da2044e626f622d68706b655f372d696e7423584104e5f56b98441f\ 710117e3d9019b5d09cde61b1d4f228353062b8a7667aa58dab2e511b922f740eb7b\ 8850a5a838bcb6c16ddc1cb6d7000e7d2e2d69867e11d73a582107834d1f44591c01\ db20acb0d7f71faa793e11f7c83619a9410a97991eef3a56eb HPKE-7 Encrypt0 with external aad and external info Ciphertext: \ d08344a101182da2044e626f622d68706b655f372d696e742358410472587451cdc6\ 5749b6724a78484c69e4a7092edec45c31aaf13a1b725b388820efb2b381bab4b52e\ feb9d6d65ff69c49b765426a6a4fd7872b3691149069394a582142a32c0ba176b205\ 3b114682189982e07506a4ac383067aa9920552e452be123b8 HPKE-0-KE COSE_Key: \ a70102024d626f622d68706b655f305f6b6503182e2001215820f135aa53a7b8d080\ 1eefc6545a8b6262d74b74015f246c11b37762767ef201ff225820ed6afc34bc882d\ 17d025cc79723caaec97006411b6b975add484362196948c4e235820182a2a509e56\ 778bf678dbc5ca76cc18fce47300815540c82d4a624b17bbe437 HPKE-0-KE KE+PSK with default aad, default info, default hpke aad Ciphertext: \ d8608443a10101a1055055ef57a8c8f1e2cd792f9e9c253a7adb5821e7dde67c8df6\ 36eb9b2349527a6bab7bd575e46995b3cb45b7edfb339ef6dbd903818353a201182e\ 044d626f622d68706b655f305f6b65a1235841042436c6d0ff2176e1a1a808737781\ a7fc7376014919b539aace84114fe6dccfb82c327719721efc5e8df87cebe7d0c28b\ 74770a2c816781a5c88f8b6ef83110a158204ca4cc64d178000d42aa6092f7c8ef5b\ d5995a33ef7c4b6d9490b105215d6293 HPKE-0-KE KE+PSK with default aad, default info, external hpke aad Ciphertext: \ Tschofenig, et al. Expires 6 August 2026 [Page 51] Internet-Draft COSE HPKE February 2026 d8608443a10101a10550ca918484db7e57fcd6a451579d04a91058218f4e49d4242d\ 4b03092402de93ba613f64d3546334581d75f09781a917eb64b5c9818353a201182e\ 044d626f622d68706b655f305f6b65a1235841043f245ce79f1a6674314e44010377\ c817b3e52e31767c45143824ebdd4275a8c02f6037267b7de937ef1e3d5331000305\ 0311b33826469b3f7213a7d3a518d1b95820efe256263376b60f788d17a590b31464\ 903587f5ef8708016697bdd27e793424 HPKE-0-KE KE+PSK with external aad, default info, default hpke aad Ciphertext: \ d8608443a10101a1055008d4b4ba3a6b7fab94fea740ddfea6ae582145dfe705c3a8\ 85a23c92abce2e9a4ceee4913ca54c12e3c7df39a5239012ce15a1818353a201182e\ 044d626f622d68706b655f305f6b65a1235841043e734095428789dee24b83790686\ 3ad7bcef86c3fb6c4839eb76463a081dc0b1c64c504ecb319ae0c64f6a6a8b7294a5\ b7d68c2cd12493673ecb9719a01343e7582061aa26e99c15baa82edd40265236cad4\ 511aa05519617cc0c22f56d455ec7e26 HPKE-0-KE KE+PSK with external aad, default info, external hpke aad Ciphertext: \ d8608443a10101a10550db52db662f81a9ae2c1cec60b79abb125821ff4bf2e65f87\ d17e74432da6da46f264543c5662a34da8b1d63c7a04f92cf4a2e3818353a201182e\ 044d626f622d68706b655f305f6b65a123584104ac44c7268c1790ef423d607b2ff7\ 5320667e20695387db9c1fe7ec4bb97b74001f33dc58c9e56353bc67a4d6820226cc\ 36e98452e912a325755537a6429c65e9582043c8fcd50f343797fc2350b7e22476a3\ 9b6370fa338a7f8cb90df438409b407c HPKE-0-KE KE+PSK with default aad, external info, default hpke aad Ciphertext: \ d8608443a10101a10550b0d6c7caf307e05561f106e44a54742f582143713d533c1f\ b2c96071d30efd30633d18ed3891e3cc6338d05fdf922a1fc82ff3818353a201182e\ 044d626f622d68706b655f305f6b65a123584104212d6e5b8b376b279515d1337519\ 7b64d18b311d1adad0df5c72480ac5b4ce87c68016824b2a952c745132132d417498\ 15d7696a117d77384188fdd7cc6176f9582059ed1ddcfd922588e541aaaf4bd89f70\ a360adfd109da2a83c5eb7b20732579c HPKE-0-KE KE+PSK with default aad, external info, external hpke aad Ciphertext: \ d8608443a10101a105506024ab7fed3cf00950e794951efbfe415821eced08e89a89\ e6184147e56c1650fd57ff514233042b6e9001170dbc060a66ab89818353a201182e\ 044d626f622d68706b655f305f6b65a1235841047aab9097da3d4c17f4bb5504d8d4\ 5f4c28ebbeccccb77b2f7a4f8f3674700554578c7a0f19586a2cf4fb0cd5926eb0e9\ Tschofenig, et al. Expires 6 August 2026 [Page 52] Internet-Draft COSE HPKE February 2026 db6733752e4f43dd9bd5996554e522ba5820839a506ff751227d9ec4db931f73517f\ 65a3ccc9d84a9595c06f7cf07fc6bd19 HPKE-0-KE KE+PSK with external aad, external info, default hpke aad Ciphertext: \ d8608443a10101a10550fda46441c4560291a6eec9da655289de5821a6b9b3342ee5\ 49f2f6dee9ab165d7631cb2a29f0d923378638cb7f5c8e648a193f818353a201182e\ 044d626f622d68706b655f305f6b65a123584104b378a7e3362bb1becf24ae2e8562\ 66da9784e20f7aaddda2a536cc355595d888e9737891b32e29c3ab5c07eb55e4f44a\ 2631529f9a2dadbcd1c5e32d8fa46ddc58203b391f81a9aabb2683dc6a371d6824d7\ 8812595cba6c97fb83798fd87eef75c7 HPKE-0-KE KE+PSK with external aad, external info, external hpke aad Ciphertext: \ d8608443a10101a105507a78d1bfef768bd0739fad341f49039658210a5f55ba415f\ a3c240ef60eab590bd91cce926c92a8762e9362bca167fd8fad844818353a201182e\ 044d626f622d68706b655f305f6b65a123584104df01fe0e86de46fcbdf83569d3be\ 4892fcbf66172b953fa5af4a4da3175b825a0a68a2497f779dae5430522942e77518\ 4c0403b6a3f57b5c49ea93775667c86c58204f835e149377345d40bddfd3e7e24793\ 19518a11b44ede7f24cfd059652094cd HPKE-1-KE COSE_Key: \ a70102024d626f622d68706b655f315f6b6503182f20022158304f65f3e8ce5db1ff\ 24f49fe236ffdcfba3214bde3c1c0bdec78d6e35b0d59d15edb4f497a1b440c7e37a\ 29f99de5bfb922583076653c742f9eb5a42d6d4f88a01ba09cb8cadad0eb570b312f\ 60ea5ff6aec15c927af3fa6976c77dec3141b893a9a697235830ec601bec4dffc923\ 9b6a0bbcdf52c9acf322a125af9658b4d145a0d2738229f21f4454e4f4a18e5c2240\ 437e66d0f6bb HPKE-1-KE KE+PSK with default aad, default info, default hpke aad Ciphertext: \ d8608443a10103a10558203f9020bb7917aad988ac4ce28ba557125cbca073f47b92\ d62ac626faea8e99d358219db8e5036cc04c9c1fdca5193d326bd865c2cf17f26a9c\ 7389e8f3db5d48753896818353a201182f044d626f622d68706b655f315f6b65a123\ 586104b224dde0932ad62723c9e8898a4c1559aaae3a6b13ebad3e39f956219a98b4\ 25430f04b20c91d206e09fc2444f9052f5683f37ee65fd3848fe7a4dc1f76add725e\ 3017e83c8d12a84845cd1d2d82d1166ee680a1bacf199a73031111d84e948858302e\ 5d980137bc7495b6a0d6b71601c1a1e75256df9d629fe05fa6e62d42e17ddcb008f3\ 62b52c2febd892232e16c2497c Tschofenig, et al. Expires 6 August 2026 [Page 53] Internet-Draft COSE HPKE February 2026 HPKE-1-KE KE+PSK with default aad, default info, external hpke aad Ciphertext: \ d8608443a10103a105582037216bdf248d82945b87a3c84435f20301e9df3b374406\ 88d24b21679a7a0ab85821a931981ba8d07236e891fbb39c0618999e67c80f6a2628\ 23a6d129c56aaf4d508c818353a201182f044d626f622d68706b655f315f6b65a123\ 5861048cd2c5b128525c051760ca792ae38c60f5d9be83091d4e904eaca8e0075df6\ d8f30738de090c203535bebcf1a6e9b6bf36e224bcd8fb5967e0a0eca0a0fbfdf5b3\ 5da3a69e3c7caac50f266a3fc11e42d087511f1b0fad6d523ae53a0bfe604c5830cc\ cd606f644126bc917ae03ba7cefb34a38a8a4e00f51b830fb459018b009c78348094\ 1f73800fc8e0b112002a07fc52 HPKE-1-KE KE+PSK with external aad, default info, default hpke aad Ciphertext: \ d8608443a10103a105582066815f04df75e4baa646152f2460695b200df8a50bbd0e\ 299dafefaf15c0532a58212dc67fc86f0206f279930dced3b6dfe726250cff8354c0\ b657fe6bcdaa6488daa9818353a201182f044d626f622d68706b655f315f6b65a123\ 5861047c52bead4335a216813ae6e4dee2659ca7105ea850317c25b0cea602c8f3f2\ 2e0141b58893ec356f33c20d6330bbaf836f158ba1ed714a04847a7813c64ac6c702\ 9674035b6bca9c78f558746e669627970d8ac3b87800e4afe2d64db3dcb57f5830b6\ 6689f6f4d536439d6b2e3f8240ae704c17679f94c63590fd6a29a03b1e32d40e2af8\ e664f622d0e5877f002882d558 HPKE-1-KE KE+PSK with external aad, default info, external hpke aad Ciphertext: \ d8608443a10103a10558209eddef4455129ccbc494aff056fe52b251224e272da90c\ 7ecd54ce94c7d45169582188ace3811de11efcd2085d7ae48ffeaa7ce401e9c991e2\ 25044c8359190d997283818353a201182f044d626f622d68706b655f315f6b65a123\ 5861046ed1710cfe5f23c768f69ae5124ea8baa65b18a1981c64e157e8f324619215\ c7878a697c004a612fe20f66c89b7b2af741cfb7e867b7c2a1b35273c2bc947ecbfc\ 868377795c296592759d3bc722bcd62bd1ca6e9fd0c70a9b16908da9b2c8445830c6\ 199481077ac37f2ec1d4b1ef1fef392e4fb9141df4293dafb794b54bdc4064a81d8d\ 8e373ad1d3e92e246066d5738f HPKE-1-KE KE+PSK with default aad, external info, default hpke aad Ciphertext: \ d8608443a10103a1055820f47c3ba696c350eaf5dfe64827bf68b315ef8cdd02f6eb\ 79b86c025f16c9b4a1582197c7f2ecf7c3f2b716ab7d4b73f97b481b222e60716210\ 534f78016c9b03413f38818353a201182f044d626f622d68706b655f315f6b65a123\ 586104507accfed015dcf0df6d1306def2ceb0452ba174ecd3e06b9d30e347e07364\ b3235ddd156f6501ab8f96a27ddd65fa2b0d54326b38c3bc6ccb592bb72a41561fea\ fa7ba3d707a9f8723c96c0c849fac454603f148c45525dfa19582e76c9a0c3583003\ Tschofenig, et al. Expires 6 August 2026 [Page 54] Internet-Draft COSE HPKE February 2026 caa89c05e657bc89efbad8e98477e85fb02ec395c0afc94547ebdca64d653e80923b\ 95fca02adf07a7e017693e68e5 HPKE-1-KE KE+PSK with default aad, external info, external hpke aad Ciphertext: \ d8608443a10103a105582018e63fad49110f7ca669baa530a3ec034c2f1770d1eaa2\ ce2a341f217d896bb558211815fb8683836dfb3704d766cb4b40dc4b1fd3ac1b2d24\ 9f8bf391d3a555169506818353a201182f044d626f622d68706b655f315f6b65a123\ 586104a4f4e17c89b7c0b522e8ec28bd24c0bab416f94b30c5fe34ac861dfb25235b\ 67aa6e5b3a9ae6e716165091f673b89e42d34c159d3017dc6278c94552927b864c18\ 918855547bd105e52143bf40d918ace0909d175c4762e0148a160db874ca0a5830aa\ 4d85b740d6f6374b5e2badfee77f4785b09fb924f08e66f5fefe36475452c4afd6b8\ 21d2709f5475a4f2e4e425757c HPKE-1-KE KE+PSK with external aad, external info, default hpke aad Ciphertext: \ d8608443a10103a1055820ef49dff5d5ba7d895181eb84e0559e17064ff6149bc74b\ 3b1cc707edffb10ed058218b25783a9d5efebf68c9a32535d50dea5335af4b28683d\ ddea0238b7ac864efe65818353a201182f044d626f622d68706b655f315f6b65a123\ 586104acb79124f34d2f82b6816d4ef4f835f6ac056fa3ed49b631136e416de1a7da\ 5b13d77ef3e99b5c3af89c4335fcec4d0b52063e3669de03469d8f65069dae4484cf\ 58027f0d1c0414575db5e4ae47d302f49aad5d6efb7eb1c827502688f245af58306c\ ca7863e2e0b35193bad7c08677f15c9497ed073df29ff1c7acb784a2d9d5c5184d9c\ 8ef64218d1561a9f36b7c38d09 HPKE-1-KE KE+PSK with external aad, external info, external hpke aad Ciphertext: \ d8608443a10103a1055820b6813d3b91fd420ce0fbb282282a0781e928bba1f2ed65\ 55ac3876ccb79139605821278ef63f7bef40a20188e88d8072a35fa49b421dfc7106\ 9a0f01abf8632b5a188f818353a201182f044d626f622d68706b655f315f6b65a123\ 5861046f6718ba3d9581817b7d6e8ba572577ca2b4c426db2e83273af0b8bbf1ee33\ d54afd913c341bbb8d3115d7b6d08b6d1fee711131c1c908877accc0214cb2c86670\ cfb647cedc0d3de474397691ff71a9f72ddfd0d8a7bea15c6ab8b1035fb723583013\ 444234c83126f8a62772aa4b9a6e7a702255557cd726a740ee18a1766ad48148d00f\ 87f6e9d418d3c68f8f8411b77a HPKE-2-KE COSE_Key: \ a70102024d626f622d68706b655f325f6b65031830200321584200d79ba4c6f1f0cf\ b40eb165353f19725907afc3d302e466f937fcd14fb3be4eb50e2d13502642e691ee\ 2f9a6ff8f9639f2af3291fdb7c3b4c2d48b9ba6963d7762e22584201d842560d1937\ 0441abf9819003efbe8ebfb6ea2d6c53eff1952aab6abd9956aa8d35642bd3b1fc8e\ Tschofenig, et al. Expires 6 August 2026 [Page 55] Internet-Draft COSE HPKE February 2026 99e5a55a8e5615240e1f5c8d3e83481307215f71d7eb06734b23584201565854ad14\ 06345de77c2a4df3715f29c2bea30b86c08ca2b756118969f5c7aeea0ed0aa10ce20\ 5ccb5428e4ffb476bf1524a3905ecb7381fef8c5011e5870b9f8 HPKE-2-KE KE+PSK with default aad, default info, default hpke aad Ciphertext: \ d8608443a10103a10558203138bee2c7c5222a490f6dc8afc1b3928d44db2df56fb4\ 032acfe1079ff9c52a5821093d059b8e0684b04d4a7a4eaeae24cbea063414467e45\ 89417511e7468410298e818353a2011830044d626f622d68706b655f325f6b65a123\ 5885040162b43abd5b8846801b7de98072cb9603536ec3a7bd30668528dc75707804\ dbca8a71e3adcae9ad7635e1107ab85441b63acb86d0252488ac7c24157460955da4\ 22010eed01508bc178962b45cb26d06d484ee72b4ac2cfc937e1d171e42483a5a5ac\ 080b83a0aa25b376facc15607d9a2ef91ebd233e2f35ef08b4dca8fb0efbe1676158\ 306417055e20b3c85bd42c94377af8ff21b5da0bacd1f62da7e0b91499158eda595b\ 40d1c9fe83361bf739577e2cc7b847 HPKE-2-KE KE+PSK with default aad, default info, external hpke aad Ciphertext: \ d8608443a10103a1055820215850dbf837415f3822d8f5d26cd15a0c146c92359b11\ b1782867d457d4378a5821dca9a96193d94c1d1a6875471f113dfa4c623fd0ce711b\ f7d4c1109bdf7930895b818353a2011830044d626f622d68706b655f325f6b65a123\ 58850400c6e8136d09b7a8acb620c13b17ac1afef18ed180cd259be1d3dda1072d96\ 40371b05e7c56911fa97aeb1c7ad54c8fd396f40e75cb5f67f17a2ea70e873b56f0e\ 5501372452c80572470b4cc341434b023b8f7d421ef1a6560670d9ac7510dc6d6cc4\ 4d4c2454ef702313759494bd5dc1198aaee2ba8005bbbcde75d688f59b15a88e1f58\ 30c17f1cae979c5ce953c68b778f0a774bcee5af484f6c59c35cfef9c811cfc87959\ 334a1c4475034e2b780ec7bb53499e HPKE-2-KE KE+PSK with external aad, default info, default hpke aad Ciphertext: \ d8608443a10103a1055820fdb5784ac8e133937727e19374513e964a7d940e4f5684\ b73ffccddc843df4445821abc32701a38c1c36b3cdd98683474ac9d01237f4a61013\ 7905c75be8520a7e7a4e818353a2011830044d626f622d68706b655f325f6b65a123\ 58850400652d2c6aad232448534aa1fbf6318956a3ca8fe3a581bc264cfb74b5c4b5\ 9675b5852f7b28c515413414faf01474c45c4111711ffab4d1541cfcaaa0a6136dbf\ 78017cdab90f57f246ba74fdbad5218bb7e57e4f645253c3802417f91587beb94af2\ 3423eb0fc295c74b42fe64d5c033bbf29a3b18548788de1010bdcc076254dd30ed58\ 3063e1f93cb9087ee33598b22f6b5f77008b4798345c4a8004b42565dc5a753dc39d\ 280117494fec9fb5ae0e28ac358470 HPKE-2-KE KE+PSK with external aad, default info, external hpke aad Tschofenig, et al. Expires 6 August 2026 [Page 56] Internet-Draft COSE HPKE February 2026 Ciphertext: \ d8608443a10103a10558206a802ccb1bd4d388862b5fe0afce78dc7fc3c08a4ee1c4\ 97fc03e2a92db02da45821329c4d048a5c81485fff9540d9ddc083d31b59c6eee09e\ 8b3787e0f50424eff01d818353a2011830044d626f622d68706b655f325f6b65a123\ 58850401f32ef361c8b9435fd85f2a762bff35d49407738e645893bc38938a046553\ 9beaa0867b3c32eb993ce0a8599e684b22fbe06527d7ea5f23809bf2a340e4310bd9\ 20005d05b63e8fdaa1428ae3bbf70e8b606b8bb364c897a1edcf54d27e56dc0fb4e4\ c89b35099465048b10531dff3101167eb081f4ce1198d66361773ce83f1420cff658\ 300189869866e44e995db469e07664386d86680cf0afba7ed0506d893124347ed12c\ 05277d04eb5ca818a83ef7d2abed40 HPKE-2-KE KE+PSK with default aad, external info, default hpke aad Ciphertext: \ d8608443a10103a1055820ca66488980e271eb113bab9c87c532ab964778274b14fd\ d1498f43760660cbdb58215915445e1b1592fc3ca8a10e066770df837e8dcf627b2d\ cdb303350a8cfdc15181818353a2011830044d626f622d68706b655f325f6b65a123\ 58850400af9a27daf713ab290e06f323585fe4e378adb3da71ee3f913d4df0ff6432\ 34d5096298388e0385b6791583dae223df7a2395c739be3456d877f2c22a60db7079\ 3b019e97cb108e5ed8a4dcc92e708f9010f0ae64410aba36ef66edb45275f4c22e61\ 3352d0ad6e2a94c645ddca1c3db4df47b0453de357c91f6dfafacb11221462060058\ 3060acf6929d7bf0496ef34937a3bea4a83b92e7ac223b9cb7b1389eac5a6fe52f62\ a7e16186005c5d9c7e3aa052b66c4f HPKE-2-KE KE+PSK with default aad, external info, external hpke aad Ciphertext: \ d8608443a10103a1055820c12e10e83ffb5d684b5dbc8987f36227b0ae5356f60eab\ 1c5cfc07733972713e5821625dad1ac818ddcd4f5847d09b661f6a80bb3ee80c85c7\ 11d1eb1fd57e6b6e9bbc818353a2011830044d626f622d68706b655f325f6b65a123\ 5885040163399875d2f44c2b62f6a241dc4e5d2d77ae2f71d48b8a4ff7015cfea98c\ 25573ca31b1fecc15ab570c6d848a9dd6cf65791cebd6fafa43b85a997caae43a6ed\ 6d000f7b7e6f33ee305779bcdb560112e82663715bacb5b5b46a17e00fbc1c7e48dd\ eea2cf7f79d6a8db02baf64ec466244d206ae933eb4ec2559603a306c5a43a36f758\ 30151440d327f5b4301017aa88a5c07df896c565e5dda60e71594c9a07dd95d16ea9\ 7f780977fe2b5e1ec9a3bb2899ec0d HPKE-2-KE KE+PSK with external aad, external info, default hpke aad Ciphertext: \ d8608443a10103a1055820d2d3de0c045b580ca7065a0b6ee0ee4a99b16df064c8c3\ b94f080503ae1bf96b58217b530401f8dfe8b7f938929169f31054f4c1b077d874da\ e6357e0299523cf309ff818353a2011830044d626f622d68706b655f325f6b65a123\ 588504001c84d1eedbed866132867ed9cb7468462f9c9a149fe92f8b719d6b2c02c1\ 10e04b1cefbdf10604a0426a24e0a11b2f1b519b1344629344a4f54bc0fe2996e9b4\ Tschofenig, et al. Expires 6 August 2026 [Page 57] Internet-Draft COSE HPKE February 2026 9e01478110bb40c4050e47d7bb2d2f99233dbc6bb71a1a60a2ccefde398fd6eaaa10\ c940825ef3f2bd824399139b9f55ba7d8c0f600c4208867778f7bd596c3c95afc758\ 3063330387cd24664cc5ebc2ad1d1f9e785c9c1c8682ab61e810595b99f6af562ca9\ 751eaef8949b746005a8aabb3d73bf HPKE-2-KE KE+PSK with external aad, external info, external hpke aad Ciphertext: \ d8608443a10103a105582035a8bd741dd4bc4eb339dcc69e91214badd6d79fff2cca\ 4088e6733b80f7d4e25821a2b8d2e530b9939d2bc3e478ca797afb14453151e294c1\ dc4a2bbaba356949dd95818353a2011830044d626f622d68706b655f325f6b65a123\ 58850401dfb9d20c07e0ba4fcc4b93e66bd94ea0b8ea94f4b336912b0d676b5367d6\ 97801e668f598dadbfbda8c375478d368209e09d51f7cfa2ad283f8d211ae13b7d23\ d801b2f56718deba752f33c8ba0aef918db14d6b901ac55072a781eb26b04cf55363\ 461604f6b0b6931f0da446f5d55fb56c82ce6989fc88129b1918335efd0fcda03558\ 30afc3fd0466c8696180429b63cc76880e877e2da59f20411572cffe8ce15ceff86e\ 78a18472c78a6286127290caf6f15f HPKE-3-KE COSE_Key: \ a60101024d626f622d68706b655f335f6b65031831200421582032df6a916a5f6f14\ 5cacd3755783f65f7f5b35ddfdc6bbe6e699c1012f296c70235820e8acbd4b527e76\ 6136f0e0ae266dafaca435e2c4326f6be8aeeea30d4ce91070 HPKE-3-KE KE+PSK with default aad, default info, default hpke aad Ciphertext: \ d8608443a10101a105508fde94810cf9df2b8f3e011dd014866458211e3b36874e1b\ 8fa028f8805bbb1f88cd29125b6cb229292eed3949060323114f26818353a2011831\ 044d626f622d68706b655f335f6b65a1235820fd114c5c260726726405b3983e92b8\ 24c76ff415bfb3a85d43266be85e436d605820db8a62e96f13814fb6b391fbd07868\ 7ec01e5430408a1ba130b8aa561106d36c HPKE-3-KE KE+PSK with default aad, default info, external hpke aad Ciphertext: \ d8608443a10101a10550e7eb3c12fba8f1a84360649e00228c035821188af3afa5ea\ 10ee723e40b0aefa2a7c1b1b05ca778c613ecc0c1f846595a5a7b5818353a2011831\ 044d626f622d68706b655f335f6b65a123582020f2e48c5b6cd52cc560c8c345050f\ 1bfd3756259bbd321704a963614646656c582002ca2aca70d04f750f32805cfc440f\ e78591f3a5c1fe6a931870ba6cad61244d HPKE-3-KE KE+PSK with external aad, default info, default hpke aad Tschofenig, et al. Expires 6 August 2026 [Page 58] Internet-Draft COSE HPKE February 2026 Ciphertext: \ d8608443a10101a105506c5121bb87c9c2f62b2c868403be8a38582113c72fe8aba5\ 5de94b9f0cea23854e8fb4dfdf87d034f0b17e366fb05f94be4364818353a2011831\ 044d626f622d68706b655f335f6b65a12358201cb2a61bbc134a03b6ba241f0bf47f\ 71a65a3b67e948f7974f94e05e2569c97458209e8495b63496b92c5bab86e7f34b55\ 5b6a3677397bf408835500188c3df93b39 HPKE-3-KE KE+PSK with external aad, default info, external hpke aad Ciphertext: \ d8608443a10101a10550f9a3efc56621cd0fa9c173feb8d486ea5821bc91169ed9a8\ 17fefa394582affb4f019ecf50cdbfc46e52ef437d708907854447818353a2011831\ 044d626f622d68706b655f335f6b65a1235820e33a5d0f7a885988058daa06eb6895\ 961f41e6b93e07314e8319ec60dd0ca8635820d38344948ce6c0fcae23835a7b3059\ dcca67057ebbb3628b30c7a44af246ca2a HPKE-3-KE KE+PSK with default aad, external info, default hpke aad Ciphertext: \ d8608443a10101a10550e21e4f3f711e3d4a40233210b6c7cb18582153dae8d74b8f\ f4377890721f44b576e9cde9c069796daa0ee1606b21b868d72560818353a2011831\ 044d626f622d68706b655f335f6b65a12358202d4c865b322326d0c42970da331d64\ 0be580266d1ff5bd48fe2d5851bac0fe7358203325793599c3f217f84542bc2523ad\ beec95c931eb53e71145f1a3f8f78843e6 HPKE-3-KE KE+PSK with default aad, external info, external hpke aad Ciphertext: \ d8608443a10101a10550784f25d8b3b8e28c2ee57f8034c2d63558213d35627b8906\ a2c6325f0bc1dcbeff96a66f00d2326b7bc347631f356dc79a1c37818353a2011831\ 044d626f622d68706b655f335f6b65a12358207ebbf54428b2c7ab5cfbb1aade2cc6\ a9556a0e58528ae576258f0d7c126585315820b610571bba5facae1b75386f5ee98e\ 3c370fd7b7070b58794e4ebfbedd876543 HPKE-3-KE KE+PSK with external aad, external info, default hpke aad Ciphertext: \ d8608443a10101a10550b0e54f4eb4dbc8d74d0403151a4c9ab65821bb0bf21a799e\ 13f522fd5d6efd495e1e0715ad541388557b9baaabd6c4f7105280818353a2011831\ 044d626f622d68706b655f335f6b65a1235820bc2dd6a7498209f6a16ce2cb8ad311\ 46e1d7601f3b7a7d916e9b8f0c4b280c1858206335338627bda61773b8abc05330f2\ d86744561fc9705df85392c3979a34aa82 Tschofenig, et al. Expires 6 August 2026 [Page 59] Internet-Draft COSE HPKE February 2026 HPKE-3-KE KE+PSK with external aad, external info, external hpke aad Ciphertext: \ d8608443a10101a105505e5a35587511620d9c95dbda458414285821ca24cea1349e\ a1bd6610cf7d64fbae3809c17b48870a1e33fae2daefe83b16caef818353a2011831\ 044d626f622d68706b655f335f6b65a12358204f16be73404f6130ce36f25b3abf38\ f1f8d574330257a3715a44182d74611c715820cf43a27483d12a7fc5a01ba05cf0b7\ 9bc9fb6c5b7108f7469c2ab8fc437d514d HPKE-4-KE COSE_Key: \ a60101024d626f622d68706b655f345f6b65031832200421582000c2029ec474be36\ 8261a61ef7dc4a3cb7951209fcc66dbab39c14ff85400320235820d01a98ed714cf0\ 8ad96c793edbae5e1f5258dd98e94a1a94d6a08adbd56ea74a HPKE-4-KE KE+PSK with default aad, default info, default hpke aad Ciphertext: \ d8608444a1011818a1054c2fb741d0c5c6977aaa2b01c35821b738d24609bcaa98ee\ 1f5f7b77eb38b9d64e5aba602154c58c12c61824631a4f0c818353a2011832044d62\ 6f622d68706b655f345f6b65a1235820a2310170dbec7095eefb7d35107c425ec256\ 6a5e859cfd80e6a56fc91cb37e3c5830635a41f1026dd93b27b73d30c9a5391c7e05\ bfc8b0ca766933f62257781c79fe6e4c2c0d1cb17edaee344fc33322a9f1 HPKE-4-KE KE+PSK with default aad, default info, external hpke aad Ciphertext: \ d8608444a1011818a1054c3cf3405adaa9331e2706668458216e3a5631d75766cb70\ 8fbda036a6e5b654f4bc3c19bfcbb7ad9ed3e5574115381a818353a2011832044d62\ 6f622d68706b655f345f6b65a123582009fe08cb84624452f285537cbc0671477338\ 7689960a3584b05cbb4ac70acb705830db74a5f8b12ea239755500670d38b3c63eae\ 4a1f0ba21b25876c427422a70a7f3cbf26a43570d266d28418c914394d2f HPKE-4-KE KE+PSK with external aad, default info, default hpke aad Ciphertext: \ d8608444a1011818a1054c6d73414c64bbef1b945b35a9582118530c7ff2e58db941\ e48ba7b1876e88a3e019bb1b92789dba0309cae6cb74ee2a818353a2011832044d62\ 6f622d68706b655f345f6b65a123582047267ddb7a6a5788a506b37d450aadffe786\ 164e6f94cf5253c8e023f181a73a583034362ce15946e700fd8bc9dccdf1cc504822\ e76e2a9250866378e85b8d1c8faeade8e5657fa9dd9e36ebaa46c3ad923e HPKE-4-KE KE+PSK with external aad, default info, external hpke aad Tschofenig, et al. Expires 6 August 2026 [Page 60] Internet-Draft COSE HPKE February 2026 Ciphertext: \ d8608444a1011818a1054c8bac033f30bf465b3c8184c25821ed9ea80bfb07d11a20\ 399d92e4d757179ae6e4ce1d9d5db67ca20fd0c85ffe35e3818353a2011832044d62\ 6f622d68706b655f345f6b65a12358200e6087d030b1e8520574f884baafdafddba7\ 1c558705cf4872aeca4629c7403758308f95cf34c40fb9ff6f3cae1f9a8e9f99058d\ 249f5feacb091b0e615e0e9f46a5bd1435439b1bd5844ee7775840003c36 HPKE-4-KE KE+PSK with default aad, external info, default hpke aad Ciphertext: \ d8608444a1011818a1054cc32577820e9fc7f1dfaaef16582146e402f02e4c45bf8d\ e3c32d36b16f520faf735f90ab843f23796880fcbd549d07818353a2011832044d62\ 6f622d68706b655f345f6b65a1235820d524b1636dd7796be27a080a9167ddf362e8\ a06eff5549572a04eaf9bbb46604583009ed3173e50ea69bd2a3f60a7252e81e1225\ 6016ae3a762b05e28174cdc853a80909b6f0be8db0aba24a48b2c975c153 HPKE-4-KE KE+PSK with default aad, external info, external hpke aad Ciphertext: \ d8608444a1011818a1054c733a1396a5fe52e4014a80355821d5b08336a933b87f03\ 26832badf4f522c942c95f0bac27c9e47bd99039360dbe5f818353a2011832044d62\ 6f622d68706b655f345f6b65a123582096d993edbd974f70b36f89a5833f745c5f2d\ ba2c34e2dd25254ab4c3309078235830244a6ae5269b99fcf817f921dfbb914a3e7a\ 8d98d7effa565c1a38b6607c5ce29a0a6ea78cd3e00a1dc1c1191f715edd HPKE-4-KE KE+PSK with external aad, external info, default hpke aad Ciphertext: \ d8608444a1011818a1054c6508d2450db84d5aafdf22645821979e63ed8bfdb38b82\ 8b5c495aa0eed1257eb0dd8784d52efc6acdb450ab3c00ec818353a2011832044d62\ 6f622d68706b655f345f6b65a1235820ff60abdde8677257c587be0228e616bfbbfc\ b2ed5c311e112fffece0ae28d4585830299c4de0445f2f588b8f9dad87b10f5195bd\ c20a65f1b0021c138304477ed35ed752694fde15c21cb4cbf5b49b8affb7 HPKE-4-KE KE+PSK with external aad, external info, external hpke aad Ciphertext: \ d8608444a1011818a1054c6a9fa48284941a3c00aaf7c8582173bfd8633fcb167664\ 09f713a4d6345c4331834876130bc6fa8e3b382914ec68b0818353a2011832044d62\ 6f622d68706b655f345f6b65a1235820a78b256072f458027fa9790f0689eb492f40\ d28622e07c6ecb81fc30c02f894c583065f9ded5cdbc30262debac57505803bce0a2\ 879a354171668ef8378bad1f2e09e84ac1cc79fd7dfbf03a773a99d8a6dc Tschofenig, et al. Expires 6 August 2026 [Page 61] Internet-Draft COSE HPKE February 2026 HPKE-5-KE COSE_Key: \ a60101024d626f622d68706b655f355f6b6503183320052158384e237eb6c934b5d9\ 48aee5db58e71b73becc1fdc6c90d45eb68975b0008ba24976fa622dbdf0848e80a6\ a222e4b0e1f85b99631307bc4b01235838940bb8c6bf6882564f1138fc7805677a68\ d2422492d3de009740f973e4e29cdd92e1942dd2f2d23526c410522376bc0c0890a6\ 425097f4a9 HPKE-5-KE KE+PSK with default aad, default info, default hpke aad Ciphertext: \ d8608443a10103a10558205adbcb6e0ff034e4c7fb8f57d8684d48a0713ccd9d9ea8\ 07e0414efee28a983758212b781241cafbce0ddc141d16a4fbb48f64eb2aed749aff\ 992400a081c9719a3d98818353a2011833044d626f622d68706b655f355f6b65a123\ 5838dd342034c2bef0bb830c781530623f7dfae57752409b4c063c08c670bc5003be\ 86d45941075d2e38e35d6b5c8da084b1eba2e05119c48d26583023ec6199b0bbf9cc\ 776ea35e34fdaa85786090f62f738179128cb37aff35f95e5d12417ea84df23daef6\ eb78117a4f8c HPKE-5-KE KE+PSK with default aad, default info, external hpke aad Ciphertext: \ d8608443a10103a1055820c801c70cd6c15c0ed4c5d31095a3d9ea5dd35a3b7ff85c\ effb49ebac170a9ff95821ab85a76a92a692a53161168a3beb7a051346cb4859d3e0\ f2047f9fe4c90131de12818353a2011833044d626f622d68706b655f355f6b65a123\ 5838b6c90aad8c11cbcb475b01f9544219dc466f6ec119d4108d35bc31cb12b2db26\ e1c8eafc5362e696490c06129a5cb4f7fecaffa5bd0d00b958307a1ff17acb7d872e\ c2bf968d6ecf7be5194175e98531359bc26db8a0293100649d3ff5dc80261c5c80fc\ 1384c17e418b HPKE-5-KE KE+PSK with external aad, default info, default hpke aad Ciphertext: \ d8608443a10103a1055820b55199d8da2f1d98276b8a6c0a6db64fde7f45c75fc468\ 10465cbe324072dee45821745d2621a784e938f5b81a742ccb209ad642502fb63210\ 0c3af8c2c9cbe013646f818353a2011833044d626f622d68706b655f355f6b65a123\ 58389cd5c81cf76b3be50a1ab36c6875d89b65f2d26355311f5c76c32ebb5fee324f\ 8faaa70fe97eaa8346edf8191529f21c58afe92d8dc56a3658309adba68d36c24323\ 0b6615bd68a7af1bc1ec51902ef11e4779dd2168fd515319fe60d7dfb4c0345fa9fa\ f53525a1d68e HPKE-5-KE KE+PSK with external aad, default info, external hpke aad Ciphertext: \ d8608443a10103a1055820ada57fa4de7c380f19c3e5b2b929b64cd838f46a8c5087\ Tschofenig, et al. Expires 6 August 2026 [Page 62] Internet-Draft COSE HPKE February 2026 3c7b84c076e8cfaa3a582185a638115f9e6036d3845bb96ccc12ff6d506200a7264e\ 524a316ec496d419c99f818353a2011833044d626f622d68706b655f355f6b65a123\ 583832dfdc226ec0637124dbf5a5c82795b860d0b80a1d6c50bbe2181ce1c8fccb7b\ f4014340a3588af77a231124e7863278e44c082dd86495f25830d386e2f8408fcb05\ d8898380101486ac601901774e065220f485f2049b11a01b0992f0ded73dfdb2341d\ 4b53d6fdf3c1 HPKE-5-KE KE+PSK with default aad, external info, default hpke aad Ciphertext: \ d8608443a10103a10558205a2b4259c8726f7b27c76ecbab67b873b5d6d4a70b0cd3\ 486d71f14236b296e4582102e54618043019f8934c2c8c56db8d92189bf4ec1f5296\ 2bcf51fc02a965ba1440818353a2011833044d626f622d68706b655f355f6b65a123\ 58381213b34c1040aa5de533d5af7cc401a7824683762da048933a292ede982a9722\ c6110351b1e98cd058705fbcca2818cff9f7b6b5bb8881f858305ab144940664bbc1\ bf1c5b3c8c76d57520d871f7238b4cd34f8a53ff72b9980ad2d05a51403df6f8e926\ bea5780cf0c3 HPKE-5-KE KE+PSK with default aad, external info, external hpke aad Ciphertext: \ d8608443a10103a10558207f86dff69987f153f499c0511ed65e655d4d34430a81bc\ 95cdacc6a107f7bfd95821142a231e1c831730c99cb634850ec08c47305bb342b279\ 4ff27c6490d3d0c3036b818353a2011833044d626f622d68706b655f355f6b65a123\ 5838fc4618571971c112d55fef10f82d2114c2fb73dc0a94182cde7bfefea6d82685\ b4bdfa1ee1947cf0d76a224c496f282e75694efcc4af5abf5830d074a192df2905b0\ 3183195149c13bf83c1dddbd2d76b40d5ef0ead641103b01ed5bb88de9a7e00e7924\ 4343231a0207 HPKE-5-KE KE+PSK with external aad, external info, default hpke aad Ciphertext: \ d8608443a10103a10558201e95d431b06ea4021049ea2eaf75546ddf41f390ddb9e7\ 376863a904c769a5b058215929dd46a1996ea5323720abd290796727915d670e6bec\ 9192317d40e7e905be79818353a2011833044d626f622d68706b655f355f6b65a123\ 583856e102688b82fcd05585bf0cdfce4e7b749dcc4c8c5e5f0afffe1987accee459\ 369e30092519b382aeb395d121467af61fb7e344bc8397ea58301776ac6367407286\ 282a9f3bb645b42d0b77b35c17190bfa18489b5d11de38cebc9ae74e845ddbd76958\ 38765da32724 HPKE-5-KE KE+PSK with external aad, external info, external hpke aad Ciphertext: \ d8608443a10103a1055820ccc5a28c0fc6ce3a77b3287c4bfa39527836d4d977ddca\ Tschofenig, et al. Expires 6 August 2026 [Page 63] Internet-Draft COSE HPKE February 2026 2995f9f231c1aa3e5858211c8d84c7bc5b41632d045448b3dd303be1facaf8308dc4\ 520ecb141f366786903e818353a2011833044d626f622d68706b655f355f6b65a123\ 5838577f7fb7d14b3cbcf4cc8cc987c9fdb8c37e4c77787091720b16ca8ce1a1eb64\ ff394100b5e30ebe141c1728c44bbe50111ed2b3cdfe80465830129a07f73d90eecc\ a1fd2c6b57dde0cf7e35e08dbfec45195576143610932eb18a65a625d83ab2932861\ a06ffafecf92 HPKE-6-KE COSE_Key: \ a60101024d626f622d68706b655f365f6b6503183420052158387a73481c0220c785\ b74d64c163e1de5d44e5390bd0fa08ee15073b58530e4085ffc8864e7a515d472177\ 58719376b1450d97bf2a669ab9b3235838dca30972462039bf863de85351d9190e87\ 938dfc8e84d55036d3ab77b8f8c75d9ce58b9cde255a254d70194cb4853134e6e375\ 583df14190 HPKE-6-KE KE+PSK with default aad, default info, default hpke aad Ciphertext: \ d8608444a1011818a1054c36d04a7d19dc55e80075d23a5821e574da31d97960f6ab\ 7175d1a5532d59c14394e24f51df359de4db10b12714e9d9818353a2011834044d62\ 6f622d68706b655f365f6b65a1235838748632655487c9a95f46258ccdfa90d04f8b\ 434fa91810c86afacef5648cafbad2ed82ea7e2c2dfab8addcc335796fec210e0fe2\ 6ec10488583020b73a418c7419830b7f9d8b6e06a645b404fb35e6cd7ce7e7e74601\ abb1d5b66ed53e823517a315cd8ce27b2fd71a48 HPKE-6-KE KE+PSK with default aad, default info, external hpke aad Ciphertext: \ d8608444a1011818a1054c797818adbf0a654fb32d614758219fdd3c0be43a6ca9eb\ b33af5563d90620ef2ae69bc9777c1d42862874b0a4ffb26818353a2011834044d62\ 6f622d68706b655f365f6b65a123583890100c00c48cb2531016da4f3a3d3094f1c2\ f03451d76e992f540147bbd8e9ccc3b3538168856cd0ce5d772fdb299f9427793fa7\ 727d9dad5830cb8dcf359251188b60eca487fb14ee1c3914cf347c6fe223dbe5fef7\ d36de4ca2ceec64ba0a50fe5296451d51b53c4a7 HPKE-6-KE KE+PSK with external aad, default info, default hpke aad Ciphertext: \ d8608444a1011818a1054c82d73212f41a6d160736112458215de02558566868de98\ 6e6bd01ecba81b47bc67dab079c69519e9f020884172c3d0818353a2011834044d62\ 6f622d68706b655f365f6b65a123583842f56ab3e5441e6c65634346a2cfb13ae8b1\ afc9a8b833d045045b57015f9e9ab7fafe6a05671e9ee29187e20cc1b5b0acf2a90b\ 402b5df1583078cf0aef816b9e8fc4f94678c98bfd1fd7999b5e44edfa2aecb64fc1\ 5a17a94350eea486dffa00a9c7ca99224d46a09a Tschofenig, et al. Expires 6 August 2026 [Page 64] Internet-Draft COSE HPKE February 2026 HPKE-6-KE KE+PSK with external aad, default info, external hpke aad Ciphertext: \ d8608444a1011818a1054c2a6fd56a8b3f6908e1111c255821b1a6735f8870342bcc\ 0906e85561781ee0126a5efe9aa8ed18d28533449f152e1b818353a2011834044d62\ 6f622d68706b655f365f6b65a12358388769dcc3b3ec1956dec6a7f75367a59c6387\ 0f2f7b3762ec7f32432495c5e73c2c23781033a9d364591a3d300426615e9f320422\ 35f42c035830604150f58d908a033a617ad608c6bc2ee2eecd55bd50571ff2472a5e\ 523a09e2a6f85818c4466836d99331a35bc410a7 HPKE-6-KE KE+PSK with default aad, external info, default hpke aad Ciphertext: \ d8608444a1011818a1054c44d92785fbf3070bb1becfde58214c17f577725046e044\ f809adda3ecc238d697c20e728bdcc4bb3720ad4765a5538818353a2011834044d62\ 6f622d68706b655f365f6b65a1235838bfc6a49e284186a6fa33ce0e7cd97e9b69f7\ 20a81559a4b3297705219bba25c54b0ab70cc38a1ddb67446c3e448167546c4620bd\ 8736a3e55830ea379d8848709112c1eef6366ab91cf6d4cf256d3c216c7733a6eae9\ c8557ca478a147db040def50e7955c1ab5819379 HPKE-6-KE KE+PSK with default aad, external info, external hpke aad Ciphertext: \ d8608444a1011818a1054cf38ab7422245935d23a66d8758212dbe21e54161712a49\ 1581fe3820e5aa386a07fc64a324fc692d455e7aa07bacea818353a2011834044d62\ 6f622d68706b655f365f6b65a12358383bc0cc314a33ffdb4e87eaf5d52d5ced617f\ 0896300c63bc25390bdcf5ff6b9f9cd4800f05864a1bae10c3b941205bd5b7b3afcb\ 1ba898c458308a745bf13677cf7ec0d2ac9a65e14bc5641ea9727d143a30f2535589\ 1572f6958f5bc9898e33c5b926deb1f1ceba2da8 HPKE-6-KE KE+PSK with external aad, external info, default hpke aad Ciphertext: \ d8608444a1011818a1054c7913f581c059c8ec72f9ab5a58214e023cd8ca3239fd2d\ 9b29a580edd711e981551abd7751a004ff47057162b4a184818353a2011834044d62\ 6f622d68706b655f365f6b65a123583872af48d87d997690e3cfaa920dac46dc6095\ 216d05b58a5323d814ea5ee6f471b4fd99d996a9663ef0148aec8904acc6ea0ddda1\ 3c7315765830bf103402453fc9b6d846ad6f3a435aae99f628b7f323552e9136cfaf\ 64a7a95de8e2656ad6b706c94e002f2410092c56 HPKE-6-KE KE+PSK with external aad, external info, external hpke aad Ciphertext: \ d8608444a1011818a1054c3b24712df521ce6daeb16d79582157122c22bb26402e9c\ Tschofenig, et al. Expires 6 August 2026 [Page 65] Internet-Draft COSE HPKE February 2026 c64b46f817ec3b11d648f1de72499442efa7ffd13b07af1c818353a2011834044d62\ 6f622d68706b655f365f6b65a12358388cb8b6f65144bc3f730feb3c40dbbe759f8a\ db2fc96a67552a431efdc7c5ec4ec78a415823e1422b532f35c7b8ee75619e46d6fc\ 9e4455a458308f628129208d995a3e5e7234680907ebcf15add2fa9579f910ad0e55\ b43e3faf5f8e8e41e1849d3e91a6ad8a5f07ef6e HPKE-7-KE COSE_Key: \ a70102024d626f622d68706b655f375f6b650318352001215820235da0a3f782d1d6\ 3883301a1f465ce5ecb9ee21b5c956dc33af969716ac10122258200bd7226e1968f5\ fca824b05749377e347ebab34dafb752941204ae153e18a7772358208c6710cca617\ 4b6c57ab2f3166a3e12d18d5915201c98b4e48ddf65568f3a73a HPKE-7-KE KE+PSK with default aad, default info, default hpke aad Ciphertext: \ d8608443a10103a10558201e7f005d9034fd70b784b478151f569c9e4116e8d9a6a8\ 71370be98fa1e2452d5821b51716881bdd056919af5fb588eefcb06200f220f48f50\ 0931bbbab04a82e03c3b818353a2011835044d626f622d68706b655f375f6b65a123\ 5841041479f005908668cb2492fb8cb8afcb9df4c0c89c11ccd18c2c3bc7fb42c931\ 2797245d5a3ab4eac0c0a87dc2cb0a2b8ce770c5757a44880257a48841639ca31e58\ 30e0ab73659cbbd3b6a43bcce5169a041599af3a8485e32d01264a0b134f11f9dcc9\ 7324b54127972b0fb93d9c11469602 HPKE-7-KE KE+PSK with default aad, default info, external hpke aad Ciphertext: \ d8608443a10103a1055820b1ffe35d48b498f0288ff46d6a61a4e90ff0befd1e1ec3\ c94537b5f9af9920955821c23e3d1f53e82f94eeddd1588c5cadf50bfaf31f1d28d2\ 96c9047ba9727ee6b22d818353a2011835044d626f622d68706b655f375f6b65a123\ 58410424929f8f874446d29dcb78c37e6a5b50f1a4680e7a23d8f0014717645a90bd\ a7b7f4bc6b920ea8ee042a644f6b1b5af8cd7e5fea40e424e3000b4c2532e3883d58\ 300bc1e619a7ff8f5b67c7e110e01f9e1018239c3c4bb3a1f63389453bdf3249b266\ a321843aba2401d42804f627d5e457 HPKE-7-KE KE+PSK with external aad, default info, default hpke aad Ciphertext: \ d8608443a10103a105582064a16aad701de8efec4c898d53d75e273dab2ee7720d54\ 4700f3f26dc1e8b4aa58212cd39835cff3f3f303dd9dae20e79c789e0d425ee04112\ f26962be476a94f0654f818353a2011835044d626f622d68706b655f375f6b65a123\ 5841047443a801c2579cc3a9683828ac1720d133dc0ea1d9c34b72dc3225aa1b203c\ 7eced7aafcca86dbda61dcc95efaacae431fe02626f390a7e97e4a8319c9d20c7f58\ 30cb47c1f7c40efdf049f874f9fe75ac7d1a494f2cf4882bfd492cc402822ab8f52a\ 51848f7e60e798dfb969c89bb44e61 Tschofenig, et al. Expires 6 August 2026 [Page 66] Internet-Draft COSE HPKE February 2026 HPKE-7-KE KE+PSK with external aad, default info, external hpke aad Ciphertext: \ d8608443a10103a1055820e413d828a5dfcfb33b686ba36a5d155327b096140f23e5\ 2b675731f2fa06ba3558213438a2918171fd8534f9e65fcc902f9cb117821f059b59\ fdd76490a37a44aeaea8818353a2011835044d626f622d68706b655f375f6b65a123\ 5841047056fd1244388c2b611cde8e10585a66974fd59724cb6bdd82f8e576c6de06\ dec1fec70238f7f0f83f13c58cad88bc38af95456427597d5314055cb67ef0380d58\ 308a5acd6f28e689c7b750291bf0a771863a0b38bb6e3d972522e0c4e96d2fac613f\ c907615e4ec8df18f0923c2488e674 HPKE-7-KE KE+PSK with default aad, external info, default hpke aad Ciphertext: \ d8608443a10103a10558207e358aa4427767452becb89d519e0fa6896ae3c41019bf\ 5ec8ef6700fe248ad858216d1f77b27b44718c523d0fd25d532546678578e5b6ded4\ f20a6a030367b673908d818353a2011835044d626f622d68706b655f375f6b65a123\ 5841042bb09d00627ab8c7ad3c224485f3b81a9a3f696f8c216b7543c37065860c86\ 5f9e18ab32654bcbb69e4a63797b838b6c040b24a6707a39f720486fa9f24c8e9658\ 30e2727f5ae33e384b37c80a9357dd2eedf9351b1422604d5883b1aeb4f32b227d1f\ 5d1c7328475ede37196bc2aaf6e131 HPKE-7-KE KE+PSK with default aad, external info, external hpke aad Ciphertext: \ d8608443a10103a1055820bbffb795e60de4a819c29f426c403685d125b32b67dadb\ ba80218ffd00faa64658217b4d6953483445bd9a5dbf07d4fd2bea23e17806e02bbc\ 8e9a042ab73c7bbd9e82818353a2011835044d626f622d68706b655f375f6b65a123\ 5841045c1d347a472f3967d2c92324fd5dca6aa26df991a06de353e2b9eb4f4cccb4\ 2e098feadd4bd9f20f109a0c78e6a3c1d4af9a86e2243a68e331fd5352b993d7c758\ 3037d79f7df4f5d20aed2922e5a449125e977b209706b8e63bc194ec3d72a29e00bb\ d0b7ab54fbb8e9619e2a57ebadce39 HPKE-7-KE KE+PSK with external aad, external info, default hpke aad Ciphertext: \ d8608443a10103a1055820a2d6dfc0464ecb11dcea7d68e5e6789f43a6361f5d59c3\ 7ed6f7bdf1e1a570b45821efc33ca5a6bc622204945b925063e7e9430792d637876b\ b4f722238d9faa33fdd7818353a2011835044d626f622d68706b655f375f6b65a123\ 58410410a71911e9fff4710a3d2e9958a7514396351bd4782e1444e221c50e59d85b\ e8831870513c71217d9047291de48f3b3ec0e92a4937ed32a7d5221a9e752f8b6f58\ 3023879441649cf5dbfc65318c6b844f250cac5b80f5c5bcc1c79549765c9ff79e54\ f26f08aa83cce9ce80f24ed134ebf7 Tschofenig, et al. Expires 6 August 2026 [Page 67] Internet-Draft COSE HPKE February 2026 HPKE-7-KE KE+PSK with external aad, external info, external hpke aad Ciphertext: \ d8608443a10103a105582002a2da5a958beef87ad0ba08837b444a2f123187df56ee\ 2f102fdc26c1520788582124ad5a1dff05de46743fa4285a4c8296b9b402798ff585\ 617b99d71483a1e872c0818353a2011835044d626f622d68706b655f375f6b65a123\ 584104cda61f9062ce00aba834383c974eaa1f10f05515861073265508f5834c0980\ d586f88cb101d7bcf8c39408bfac13004746c96ecb33974d98869b5be16d6cfb9358\ 30677210dede124a21c73b75d43d70597b512e6dd7b467bcd3f809347c039ebfab97\ 2c41db766608113bf178aeeef89b62 HPKE-0 COSE_Key:: \ a70102024e626f622d68706b655f302d696e7403182320012158201978838d5d7cec\ cf63ef1b5206e7bf6e7878eda9fffef7f9372174559bb915b5225820ce11b8ec4906\ 471126f125f8309fa6d535b88bc2902659b2ec311f2210a0ecf1235820d584d0f00d\ 9ac070e310e07af82af13f8f5ccf8c48feb74a9f5e9ac7e434d012 HPKE-0 Encrypt0+PSK with default aad and default info Ciphertext: \ d08344a1011823a2044e626f622d68706b655f302d696e742358410436497c25f707\ c15c87f902d1e21c3cabb8d298511eb5a23aa5ca54846d296923539927ccb6e12c5d\ 2ea31e0322be9052881e1908463f74218759abaeb7acc8ee5821460f6df2872c7719\ 0f2d109b40f9387738b161a11af42af43806afa23a2f43ea8c HPKE-0 Encrypt0+PSK with external aad and default info Ciphertext: \ d08344a1011823a2044e626f622d68706b655f302d696e742358410408e74886e267\ b409c5813e6ed9a5f8b142397b64d3266c03d124a4899265465d6d1c3d85e72ca170\ c59f6748d6a314b81e065affa6c2a6a2b17d7f5e991a9f3258213fee4c1fb2daf759\ 7130bf6777ff4c617e474ab4ae87df303f8c24575022f76f55 HPKE-0 Encrypt0+PSK with default aad and external info Ciphertext: \ d08344a1011823a2044e626f622d68706b655f302d696e7423584104d27a3f163efa\ 768558406af61bde46d8ddedf9ac6fbb21d737eabf5906c7f7f68f469b027d22d396\ 8692279cc4d45d937823486e0f3a118605778921b9e4d0775821d33af1cf7b36a32c\ 21263ddf2257f85ace2257797fc9ce3b8362f7a71d7775c618 HPKE-0 Encrypt0+PSK with external aad and external info Tschofenig, et al. Expires 6 August 2026 [Page 68] Internet-Draft COSE HPKE February 2026 Ciphertext: \ d08344a1011823a2044e626f622d68706b655f302d696e7423584104a1dbd4acd8f6\ 9bc5e38f4bdaff6101aa8ecee2d637eee96f495174209a1e7fb27a934f3b17329a0f\ b93c3cd76ceb339c6ea4bee4b950792c060ff686b50147135821c9ecd3b87eb93f19\ c7f220a9afbf7c3f0d8bc35766818c9f49148563ded4cd5de0 HPKE-1 COSE_Key:: \ a70102024e626f622d68706b655f312d696e740318252002215830a07787376d7be3\ aefad3a37787f366fb5b9db711ea52da6007d6c0415edea639a3749f35e20b5db7fd\ 3f1acfa94fe88d22583093e13666684a788a3ddbdb3747923fccd850f072574b7a3f\ bc4ce7bd810de7d0754ee5e0763061e3615ccac4a6231490235830a29d238c81ec58\ 17c4ad1b8f6e6f796ba76d6ed3bff6c730531c8469bf7e08c30e8645f690d6adc12a\ 4411953082467a HPKE-1 Encrypt0+PSK with default aad and default info Ciphertext: \ d08344a1011825a2044e626f622d68706b655f312d696e7423586104df5de432eca4\ 006ac093375950771fb12d1b61b1bc8498c2a04a4b0ea42130afb07fed7ae45e0de4\ f51f872897440f16c06fe23c768f2663def46b6c5340261f45a8427d9da07e058e69\ 599b62e6712ed7e04704194900cd4f7a13e5d600b2e558212ed9d3916151acc3cc24\ 7a6b5cfff03595f4bffb5e26d4a98ecdac227ffbd2d211 HPKE-1 Encrypt0+PSK with external aad and default info Ciphertext: \ d08344a1011825a2044e626f622d68706b655f312d696e7423586104a218f4c737e2\ 53d3b87094017731469274d9df3eb676192ad68e9fbad4523b51d1555b82e8780a79\ 49055188fe745234d1d75574f2b5ba944c5e3faab398d44477d579d7bdd6389e55f3\ 48d119eb9c022d465002381be0c3afb9674fbe016f4058217d4b45a3b68278465c57\ cc1b3acac76b9271213ff89dc7ee1208cbfa5d9ef47607 HPKE-1 Encrypt0+PSK with default aad and external info Ciphertext: \ d08344a1011825a2044e626f622d68706b655f312d696e7423586104d116a00b8ee8\ 24c1b6781c91d9fb4830928b963feacd9824c232f0f4f5b71a04a5e0be4149086381\ 32ab4c758db22f4c6e37bfe8d2903812cceef4c386e65529d102693f8c0c88ef9b94\ 8e06d9a6d6afdb29a8b781947af95b5ea00c99ca56ed582160e20429a820e789310f\ 9af083fbf818141cf5a8ee186109f003941c3f05194d92 HPKE-1 Encrypt0+PSK with external aad and external info Tschofenig, et al. Expires 6 August 2026 [Page 69] Internet-Draft COSE HPKE February 2026 Ciphertext: \ d08344a1011825a2044e626f622d68706b655f312d696e74235861044aae7f5eb6ff\ 9aa01746b686d6d3fb70a899992c85387d81419ca412e3321863e89a3f758e8e0454\ dadf8da49d510dcedea55f5bd4a21c05ac8d5adee32c3885b50592bdb10840840e16\ 9aa9617e53f919d03a9e4eee8ba9cedeea06296a59d75821ad5a3f69d0bc2502d480\ ba69622367278507ed68ff5c96ce5cfc742450e52cdb6a HPKE-2 COSE_Key:: \ a70102024e626f622d68706b655f322d696e740318272003215842010ff539d3b9e6\ fc491c324a1fccf71e4b3dca99c4ca3bbcdd715cb7732109b846f2c7a08b96fec81f\ 04a34c5fb694adb551a4f8e11cc336441378bd05471b79b70b22584200ebefdb1bff\ b05f3eff770ec11b2b880a0a8f9f853297006e8db147b5e5cf34709e3ce71930d3c6\ 1ca1ddc7f33322323aa8dcec47748a503162aab814698f504a272358420164e63b64\ 4aeb24c393ba75243505a6f77f9c3acaf4f45925ec0d9a93f2838c46665449adae9d\ 4f68fd02e504bc01032fff52c57281fd9f01dff04bc714d80a1b1f HPKE-2 Encrypt0+PSK with default aad and default info Ciphertext: \ d08344a1011827a2044e626f622d68706b655f322d696e74235885040019b47bcd96\ dddd5feb25b470146d1cf0c09f20d8e642468160835db40e29f25f2d25664afe2bbb\ 90daaebda1238ef5bb19ff321bde00da48764cd8a7270476e5e000fa4f7a92e769f7\ aa71c06dda3397ef0f9a2b11e26571604d034b3c7c3ec07e0df4c6366377053e7230\ efcb77cb123d40ad0e9513e54338c8d20443e4fc6aff2b27582115e3bbca19faa6f6\ 1a7582db14aa58433d6876716c796e39b156e97fa4e0f5ecfd HPKE-2 Encrypt0+PSK with external aad and default info Ciphertext: \ d08344a1011827a2044e626f622d68706b655f322d696e742358850401abc01f5afc\ 1dfbc2b40adf647f863bfa62c9ac2bc059e8678c3d1666acd150f4a0b7eb3a9b71e9\ f5c617d89744ff529370d55a9ef4176b1265882611232e484d4701690e2e3dd1d184\ b6e5cf202d1983d39e396f3ad776cd97f2760e1a570ca71f8ae29902a80c2f462eaf\ da610ff9f03867fff20742816838efb536fd501f6ca10dc058213245639008b74fc5\ c71f37f3c302f94d54e95061dc14b86c59681d2b242c1d1de8 HPKE-2 Encrypt0+PSK with default aad and external info Ciphertext: \ d08344a1011827a2044e626f622d68706b655f322d696e742358850401b85a75afd2\ d4832df126acb39630b1ecf97cfeba280bfbed6f0c3008daa590635740d7b4fdff28\ 070e2936a5b7bbb4772b897c548da2133133a6da63de96ef87a60013d6fb0195b5eb\ 9559b8f8d9a6fa12ae3bda7e3f7b75eef0e420c3fff312044c6a87a33e429408a8d0\ 7d27099cd4e1c0d1f61c38133b821ab1881a419a395f32d85821640e4aac586afbc9\ Tschofenig, et al. Expires 6 August 2026 [Page 70] Internet-Draft COSE HPKE February 2026 489818406f1f69bb30884cd01f5dbcf8bc8fc7ab6b26edebbb HPKE-2 Encrypt0+PSK with external aad and external info Ciphertext: \ d08344a1011827a2044e626f622d68706b655f322d696e7423588504001f4e8064b1\ 74c08064fb07a48e73c92ec41073f74fd043a33cac2eb2b5a39679c15e20b8d228ce\ 93964a77f0766e460614114ac3beb2f6baec2675823821e81ef200e0b9c902e74524\ 1db2a85e3cf7717e2e61f8824a3fd8fb0d1403b367da7bb42fe63a2ed1ac4ce42aa2\ 9853d4a1dae37f4eef0a1193225d78811f1692943a81c5c15821188905cf7d36da69\ 3355ba05457fd6039d5c1cd1f49185817d70e737b8da629978 HPKE-3 COSE_Key:: \ a60101024e626f622d68706b655f332d696e7403182920042158209f898a80cc4290\ dfdf261d0a90571095afccd022b65f609fb7cbfc144b721539235820881c29bbf697\ 0ef15bef05e2b6350ceed8cfcc77a7ce141e9a8ff99b0d998043 HPKE-3 Encrypt0+PSK with default aad and default info Ciphertext: \ d08344a1011829a2044e626f622d68706b655f332d696e742358202bf99fd198dfe5\ 0851ad960a2d593fe8ad32a9b84a304e7eaa3feef510609d105821322a3cb0425a6b\ 9735ec81020f7a8f124de35b9c6788623bca0309d239677985b8 HPKE-3 Encrypt0+PSK with external aad and default info Ciphertext: \ d08344a1011829a2044e626f622d68706b655f332d696e742358205df8c7147ca3a6\ 5d94fffcacc61ed49a3790cad79534f31df74a91fb74b60f0c58219ed975688367df\ 7f8264585cc25ea668cad87824b0b2eadd9984e530b904961c8a HPKE-3 Encrypt0+PSK with default aad and external info Ciphertext: \ d08344a1011829a2044e626f622d68706b655f332d696e742358202a3900a4fbdd71\ 4b7624be04df2b031c63d9c9a852b788b0572da47b56a11b4e5821ac8087a1bbb462\ ccfa9b78f7c4e040e6041014ca783af8b754dddf52b72b0ca3f1 HPKE-3 Encrypt0+PSK with external aad and external info Ciphertext: \ d08344a1011829a2044e626f622d68706b655f332d696e742358208bed4488608e6e\ Tschofenig, et al. Expires 6 August 2026 [Page 71] Internet-Draft COSE HPKE February 2026 a3e3b10e33d7cb35d106a378e56ceddb9b421201254516285b58214a1304836a432f\ c64fbfd0f445ae464a686c950e0fefc6ca1d6cef99b9ad8a7865 HPKE-4 COSE_Key:: \ a60101024e626f622d68706b655f342d696e7403182a200421582098f335c76496e8\ 1d70b464b7168ca9331ca28bf6077db774fb8a652a98466151235820e06b4e6d7d1e\ 7c5feabc632c61cfb7761163608b5d5e1c82a1d9ffbc4b449f4c HPKE-4 Encrypt0+PSK with default aad and default info Ciphertext: \ d08344a101182aa2044e626f622d68706b655f342d696e74235820773768059571f7\ 487c63dbbb6684932a13f8782a8865a721c1f91899efb91958582109794195e1ccbc\ f3a4091254df0b980e3dc2a4f76a16f91d10106bccd4e17ec0b1 HPKE-4 Encrypt0+PSK with external aad and default info Ciphertext: \ d08344a101182aa2044e626f622d68706b655f342d696e742358204972c7ccf0072b\ fcca44cd334b6170895e59bc08ac24598b9dc024c8537ba234582185c48849033c56\ 2fe8cd0fb110b96546b1f9fb0a956462b8803501a0f342b36f1b HPKE-4 Encrypt0+PSK with default aad and external info Ciphertext: \ d08344a101182aa2044e626f622d68706b655f342d696e74235820edeabe2d694177\ e36bd06120e11c45a1d78f64336c5a9ef6f3a09f5adfc42b0b582188d2a43d93aacc\ 89bd29e3efd7be8b56d8d3c02b3be1da7f5ce8b55f4b93190334 HPKE-4 Encrypt0+PSK with external aad and external info Ciphertext: \ d08344a101182aa2044e626f622d68706b655f342d696e74235820a4bcb538ad59e8\ 6e0e1cf8b615eee457eee2ce659c88fb263fc9d064a3022f145821ded166fc8867b6\ b45628630ee777df2e47a03a81f00c961c1443d225182b01b835 HPKE-5 COSE_Key:: \ a60101024e626f622d68706b655f352d696e7403182b20052158388a68a40d28b469\ ca93ef6ab8f4095e0c467ed7da367ec674ea966d23773dfc3ad39765409f9c9f1c34\ 900c355777a9a76ddbf3e2e06e0141235838e86c18e103423df47ed171fc82f8d398\ adfb61bebc17ed35eb85246bfba090e46841dadedf5f1049433ed3a875882a934fb7\ 07588a2d12d5 Tschofenig, et al. Expires 6 August 2026 [Page 72] Internet-Draft COSE HPKE February 2026 HPKE-5 Encrypt0+PSK with default aad and default info Ciphertext: \ d08344a101182ba2044e626f622d68706b655f352d696e742358386925a3a6a036a2\ d76e66ca435f712055a771c3d2b744e8b8e0ad01534ac236b1d8c3b7741876e7a92f\ 8646f3b7cefc4236914698fe93c7785821965d22abb1540da8024724d12a8fd848e7\ 9e2b9cd2f74c44e0e85166853e98b1d8 HPKE-5 Encrypt0+PSK with external aad and default info Ciphertext: \ d08344a101182ba2044e626f622d68706b655f352d696e742358387b8c8969d60d6f\ a9668453cf4dd9e73d769a362a0892e754ee091ed7de93964648795a35613eda69a4\ b164d43abee4560c7c3604fa9dafcc5821c82bea6fd7f13c29f3a4931159eb8caf52\ 9cbafdd677c2354ed5e6accf84a55999 HPKE-5 Encrypt0+PSK with default aad and external info Ciphertext: \ d08344a101182ba2044e626f622d68706b655f352d696e742358389a4882d84ca735\ 9da36adf7a80a72feaed07e32014aacabdebea553868f3482b15cc42c573c6185f3b\ a4744d22df70ad99b74e68702944a858210a23b921a2a884507b661239bd79302701\ f3a5b479f97f3260681b9d4185da5920 HPKE-5 Encrypt0+PSK with external aad and external info Ciphertext: \ d08344a101182ba2044e626f622d68706b655f352d696e74235838bdfc9d7a69532d\ 605cd20c454713f2bba183566e7d5814535e4648b239fb2a1845e8030718ff0243de\ 3d854d25dc0cb3fc87fc692224c79558213c73d2bcf43ec29f3a91306567d2903532\ b03e4224948d702e5be80ee9e9644f9d HPKE-6 COSE_Key:: \ a60101024e626f622d68706b655f362d696e7403182c2005215838958b1eb8523293\ b880d8744265760378b4f9a72f9ab31c9147205207bfcc114186347f030f3fd894d7\ a5b9e385154141d6e5c41e06e977032358387063a27888d7919aff93704896ec21a4\ d36312d5a101fac8f75183603fbd718b5aa68a33eeaa5c8ac1d4e400c938976c6e0d\ a5080f2e33ad HPKE-6 Encrypt0+PSK with default aad and default info Ciphertext: \ d08344a101182ca2044e626f622d68706b655f362d696e74235838e5b4599601b2bb\ Tschofenig, et al. Expires 6 August 2026 [Page 73] Internet-Draft COSE HPKE February 2026 a65b4eccd053a4163c70ba55c47b6b2cdbcbd7da4301ba954aa2e106e342acf4557a\ 68ef1d9fed298ce10a5489fb01006f5821aab8bdac5bb7e89199c16293caa5ce057a\ 0a03de3b643d885665866fdf9548b6b2 HPKE-6 Encrypt0+PSK with external aad and default info Ciphertext: \ d08344a101182ca2044e626f622d68706b655f362d696e74235838535c3766b98650\ daeef42882dfe251e4502faa645a315fad0eaf0daa08c68366cf281b3a0e0924fc87\ f83d8e6462cd039907b9ee7fccbadd5821d10bfa98fbff244a4a7ff6940bad877fad\ 8e7bab901a503a51b365f50ee6baaada HPKE-6 Encrypt0+PSK with default aad and external info Ciphertext: \ d08344a101182ca2044e626f622d68706b655f362d696e742358387b1e949b71d32c\ 02236d08f29afebc7f12c14e5e21e5909683ee9ce2cb804b42d6134a88290a38f92f\ 163934329c01d70b855aa0127f660658214860e64ac9613b9188fbe659a89fde3fbb\ f87e05d828bed3112e039ee1060c5914 HPKE-6 Encrypt0+PSK with external aad and external info Ciphertext: \ d08344a101182ca2044e626f622d68706b655f362d696e74235838f8133adda20c17\ be5cce697b83cd305a9304f596f663440a2547cdd86afc4ec3b061b8ab18e886bfdc\ aad18164f35da4337dad314e63ba5a58216023c82c3ae28723cc8396d523d6946948\ 1b67edbfaca4df0a6bde5f472398716b HPKE-7 COSE_Key:: \ a70102024e626f622d68706b655f372d696e7403182d2001215820a60f63d47f6e4a\ 9010c65140f827f05cd04bc45ba2f75e8d9aee0ebb6d519ffe225820b1e33d1b7202\ 11dcbb7b58694fd45bad75f494656ffa754505d80044c1d1f5fd235820cff95cf1ce\ 5c67edcb20881bc02829d870f5f50cdaa03d1e1522c67505b6d5f4 HPKE-7 Encrypt0+PSK with default aad and default info Ciphertext: \ d08344a101182da2044e626f622d68706b655f372d696e7423584104df99cbe182c0\ 41a6502415fdedfc22b90bfcd33879dc9bc9e30b9ddc74b3a837acc71f09ad252180\ bd01da4df7b7487701ef6a80b35738e9c1f37cf40675bc4b58213da7027ac0e3943f\ df967e75bac20fd621d1726220813b416361c95e32557b4dbc Tschofenig, et al. Expires 6 August 2026 [Page 74] Internet-Draft COSE HPKE February 2026 HPKE-7 Encrypt0+PSK with external aad and default info Ciphertext: \ d08344a101182da2044e626f622d68706b655f372d696e74235841041cb6cdbeb778\ 329f4812be9da0169ac0510646a5b7d63d7ca845241c8d6200d9489be511fdc12892\ 0a3bc0998312dc0db82b314fbb2e046c7bc20ff5afe767f7582112b9b197cabfd884\ 55936d8037908bffe7b07c2953bec1c0b3b963c9fc74a8716d HPKE-7 Encrypt0+PSK with default aad and external info Ciphertext: \ d08344a101182da2044e626f622d68706b655f372d696e7423584104467cc0f1d194\ ea0dde9dc946d67ef89b7bb4026617bf68cef65d8127077a5209334a057e2674d213\ 3278d729595fd51a1556ee8f9df91acdae106671bdbaf2885821d2786254e1311ca4\ f884717a60d1b493b98cfe44be88d2820c7585e57cdcb2c8be HPKE-7 Encrypt0+PSK with external aad and external info Ciphertext: \ d08344a101182da2044e626f622d68706b655f372d696e7423584104f62055c9d997\ d492879363ee13e4cdf676172c7cdf24d27e18befab5886fe93228306646f05a06c7\ ac2d807301ea997374a3aee90b4c12c8dca348ea93fae5425821e831f27b7d99e448\ 97f409648e54594cc5f3ff1fb184979d97a5af5799b6c0ca64 Authors' Addresses Hannes Tschofenig University of Applied Sciences Bonn-Rhein-Sieg Germany Email: hannes.tschofenig@gmx.net Orie Steele (editor) Tradeverifyd United States Email: orie@or13.io Daisuke Ajitomi bibital Japan Email: dajiaji@gmail.com Tschofenig, et al. Expires 6 August 2026 [Page 75] Internet-Draft COSE HPKE February 2026 Laurence Lundblade Security Theory LLC United States Email: lgl@securitytheory.com Michael B. Jones Self-Issued Consulting United States Email: michael_b_jones@hotmail.com URI: https://self-issued.info/ Tschofenig, et al. Expires 6 August 2026 [Page 76]