Internet Engineering Task Force (IETF) R. Housley Request for Comments: 8619 Vigil Security Category: Standards Track June 2019 ISSN: 2070-1721
Algorithm Identifiers for the HMAC-based Extract-and-Expand Key Derivation Function (HKDF)
Abstract
RFC 5869 specifies the HMAC-based Extract-and-Expand Key Derivation Function (HKDF) algorithm. This document assigns algorithm identifiers to the HKDF algorithm when used with three common one-way hash functions.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8619.
Copyright Notice
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The HKDF algorithm [RFC5869] is a key derivation function based on the Hashed Message Authentication Code (HMAC). This document assigns algorithm identifiers to the HKDF algorithm when used with three common one-way hash functions. These algorithm identifiers are needed to make use of the HKDF in some security protocols, such as the Cryptographic Message Syntax (CMS) [RFC5652].
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.
In this specification, values are generated using ASN.1 [X.680] using the Basic Encoding Rules (BER) and the Distinguished Encoding Rules (DER) [X.690].
This section assigns three algorithm identifiers to HKDF [RFC5869] used with three common one-way hash functions that are specified in [SHS]: SHA-256, SHA-384, and SHA-512. When any of these three object identifiers appear within the ASN.1 type AlgorithmIdentifier, the parameters component of that type SHALL be absent.
The specification of AlgorithmIdentifier is available in [RFC5911], which evolved from the original definition in X.509 [X.509-88].
This section contains the ASN.1 module for the HKDF algorithm identifiers. This module imports types from other ASN.1 modules that are defined in [RFC5912].
Despite the simplicity of HKDF, there are many security considerations that have been taken into account in the design and analysis of this construction. An exposition of all of these aspects is well beyond the scope of this document. Please refer to [EPRINT] for detailed information, including rationale for the HKDF design.
One object identifier for the ASN.1 module in Section 3 was assigned in the "SMI Security for S/MIME Module Identifiers (1.2.840.113549.1.9.16.0)" registry [IANA-MOD]:
Three object identifiers for the HKDF algorithm identifiers were assigned in the "SMI Security for S/MIME Algorithms (1.2.840.113549.1.9.16.3)" registry [IANA-ALG]:
[EPRINT] Krawczyk, H., "Cryptographic Extraction and Key Derivation: The HKDF Scheme", Proceedings of CRYPTO 2010, August 2010, <https://eprint.iacr.org/2010/264.pdf>.