(No Working Group) G. Amringer Internet-Draft January 12, 2020 Intended status: Informational Expires: July 15, 2020 Use of Static-Static ECDH in JSON Object Signing and Encryption (JOSE) draft-amringer-jose-ecdh-ss-00 Abstract This document defines how to use the Static-Static mode of ECDH in JSON Object Signing and Encryption (JOSE). Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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 July 15, 2020. Copyright Notice Copyright (c) 2020 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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Amringer Expires July 15, 2020 [Page 1]
Internet-Draft January 2020 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Notation and Conventions . . . . . . . . . . . . . . . . 2 2. Key Agreement with Elliptic Curve Diffie-Hellman Static- Static . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.1. Header Parameters Used for ECDH Key Agreement . . . . . . 3 2.1.1. "spk" (Sender Public Key) Header Parameter . . . . . 3 2.1.2. "apu" (Agreement PartyUInfo) Header Parameter . . . . 3 2.2. Header Parameters Used for Key Encryption . . . . . . . . 4 2.2.1. "iv" (Initialization Vector) Header Parameter . . . . 4 2.2.2. "tag" (Authentication Tag) Header Parameter . . . . . 4 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 4. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1. Normative References . . . . . . . . . . . . . . . . . . 5 4.2. Informative References . . . . . . . . . . . . . . . . . 6 4.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction The Internet Research Task Force (IRTF) JOSE Working Group defined the ECDH-ES as a key agreement mechanism in the JOSE context. This document defines how to use the ECDH key agreement mechanism in Static-Static mode in JOSE in an interoperable manner. This document defines the conventions to use in the context of [RFC7516] 1.1. Notation and Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. The JOSE key format ("JSON Web Key (JWK)") is defined by [RFC7517] and thumbprints for it ("JSON Web Key (JWK) Thumbprint") in [RFC7638]. 2. Key Agreement with Elliptic Curve Diffie-Hellman Static-Static This section defines the specifics of key agreement with Elliptic Curve Diffie-Hellman Static-Static, in combination with the Concat KDF, as defined in Section 5.8.2.1 of NIST.800-56A [1] for use as a symmetric key to wrap the CEK with the "C20PKW", "XC20PKW", "A128KW", "A192KW", "A256KW" algorithms, in the Key Agreement with Key Wrapping mode. Amringer Expires July 15, 2020 [Page 2]
Internet-Draft January 2020 This mode is used as defined as the atlernate way for ECDH-ES in Section 4.6.2 of RFC7518 [2] where the "apu" parameter MUST represent a random 512-bit value (analogous to PartyAInfo in Ephemeral-Static mode in [RFC2631]). The following "alg" (algorithm) Header Parameter values are used to indicate that the JWE Encrypted Key is the result of encrypting the CEK using the corresponding algorithm: +-----------------+-------------------------------------------------+ | "alg" value | Key Management Algorithm | +-----------------+-------------------------------------------------+ | ECDH-SS | ECDH-SS using Concat KDF for use directly as a | | | symmetric key | | ECDH-SS+C20PKW | ECDH-SS using Concat KDF and CEK wrapped with | | | C20PKW | | ECDH-SS+XC20PKW | ECDH-SS using Concat KDF and CEK wrapped with | | | XC20PKW | | ECDH-SS+A128KW | ECDH-SS using Concat KDF and CEK wrapped with | | | A128KW | | ECDH-SS+A192KW | ECDH-SS using Concat KDF and CEK wrapped with | | | A192KW | | ECDH-SS+A256KW | ECDH-SS using Concat KDF and CEK wrapped with | | | A256KW | +-----------------+-------------------------------------------------+ 2.1. Header Parameters Used for ECDH Key Agreement The following Header Parameters are used. 2.1.1. "spk" (Sender Public Key) Header Parameter The "spk" (sender public key) value created by the originator for the use in key agreement algorithms. This key is represented either directly as a JSON Web Key [JWK] public key value, or encapsulated inside a JWE encoded using the compact serialization. The JWK MUST contain only public key parameters and SHOULD contain only the minimum JWK parameters necessary to represent the key; other JWK parameters included can be checked for consistency and honored, or they can be ignored. This Header Parameter MUST be present and MUST be understood and processed by implementations when an algorithm from this document is used. 2.1.2. "apu" (Agreement PartyUInfo) Header Parameter The "apu" (agreement PartyUInfo) value for key agreement, represented as a base64url-encoded string. Its value contains a random 512-bit value. Use of this Header Parameter is REQUIRED. This Header Amringer Expires July 15, 2020 [Page 3]
Internet-Draft January 2020 Parameter MUST be understood and processed by implementations when an algorithm from this document is used. 2.2. Header Parameters Used for Key Encryption The following Header Parameters are used when the chosen "alg" algorithm includes a key encryption step. 2.2.1. "iv" (Initialization Vector) Header Parameter The "iv" (initialization vector) Header Parameter value is the base64url-encoded representation of the 96-bit or 192-bit nonce value used for the key encryption operation. This Header Parameter MUST be present and MUST be understood and processed by implementations when an algorithm from this document is used. 2.2.2. "tag" (Authentication Tag) Header Parameter The "tag" (authentication tag) Header Parameter value is the base64url-encoded representation of the 128-bit Authentication Tag value resulting from the key encryption operation. This Header Parameter MUST be present and MUST be understood and processed by implementations when these algorithms are used. 3. IANA Considerations The following is added to the "JSON Web Signature and Encryption Algorithms" registry: o Algorithm Name: "ECDH-SS" o Algorithm Description: ECDH-SS using Concat KDF o Algorithm Usage Location(s): "alg" o JOSE Implementation Requirements: Optional o Change Controller: IESG o Specification Document(s): Section 2 of [RFC-THIS] o Algorithm Analysis Documents(s): [RFC8439] o Algorithm Name: "ECDH-SS+C20PKW" o Algorithm Description: ECDH-SS using Concat KDF and "C20PKW" o Algorithm Usage Location(s): "alg" o JOSE Implementation Requirements: Optional o Change Controller: IESG o Specification Document(s): Section 2 of [RFC-THIS] o Algorithm Analysis Documents(s): [I-D.irtf-cfrg-xchacha] o Algorithm Name: "ECDH-SS+XC20PKW" o Algorithm Description: ECDH-SS using Concat KDF and "XC20PKW" o Algorithm Usage Location(s): "alg" o JOSE Implementation Requirements: Optional o Change Controller: IESG o Specification Document(s): Section 2 of [RFC-THIS] o Algorithm Analysis Documents(s): [I-D.irtf-cfrg-xchacha] Amringer Expires July 15, 2020 [Page 4]
Internet-Draft January 2020 o Algorithm Name: "ECDH-SS+A128KW" o Algorithm Description: ECDH-SS using Concat KDF and "A128KW" o Algorithm Usage Location(s): "alg" o JOSE Implementation Requirements: Optional o Change Controller: IESG o Specification Document(s): Section 2 of [RFC-THIS] o Algorithm Analysis Documents(s): [I-D.irtf-cfrg-xchacha] o Algorithm Name: "ECDH-SS+A192KW" o Algorithm Description: ECDH-SS using Concat KDF and "A192KW" o Algorithm Usage Location(s): "alg" o JOSE Implementation Requirements: Optional o Change Controller: IESG o Specification Document(s): Section 2 of [RFC-THIS] o Algorithm Analysis Documents(s): [I-D.irtf-cfrg-xchacha] o Algorithm Name: "ECDH-SS+A256KW" o Algorithm Description: ECDH-SS using Concat KDF and "A256KW" o Algorithm Usage Location(s): "alg" o JOSE Implementation Requirements: Optional o Change Controller: IESG o Specification Document(s): Section 2 of [RFC-THIS] o Algorithm Analysis Documents(s): [I-D.irtf-cfrg-xchacha] 4. References 4.1. 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, <https://www.rfc-editor.org/info/rfc2119>. [RFC2631] Rescorla, E., "Diffie-Hellman Key Agreement Method", RFC 2631, DOI 10.17487/RFC2631, June 1999, <https://www.rfc-editor.org/info/rfc2631>. [RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", RFC 7516, DOI 10.17487/RFC7516, May 2015, <https://www.rfc-editor.org/info/rfc7516>. [RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517, DOI 10.17487/RFC7517, May 2015, <https://www.rfc-editor.org/info/rfc7517>. [RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK) Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September 2015, <https://www.rfc-editor.org/info/rfc7638>. [RFC8439] Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF Protocols", RFC 8439, DOI 10.17487/RFC8439, June 2018, <https://www.rfc-editor.org/info/rfc8439>. Amringer Expires July 15, 2020 [Page 5]
Internet-Draft January 2020 4.2. Informative References [I-D.irtf-cfrg-xchacha] Arciszewski, S., "XChaCha: eXtended-nonce ChaCha and AEAD_XChaCha20_Poly1305", draft-irtf-cfrg-xchacha-01 (work in progress), July 2019. 4.3. URIs [1] https://csrc.nist.gov/publications/detail/sp/800-56a/rev-3/final [2] https://tools.ietf.org/html/rfc7518#section-4.6.2 Author's Address Guillaume Amringer Canada Email: g.amringer@gmail.com Amringer Expires July 15, 2020 [Page 6]