LMS

Stateful Hash-Based Signature Schemes (Stateful HBS) such as Leighton-Micali Signature (LMS), Hierarchical Signature System (HSS), eXtended Merkle Signature Scheme (XMSS), and XMSS^MT combine Merkle trees with One-Time Signatures (OTSs) to provide signatures that are resistant against attacks using large-scale quantum computers. Unlike conventional stateless digital signature schemes, Stateful HBS have a state to keep track of which OTS keys have been used, as double-signing with the same OTS key allows forgeries.

This document provides guidance and catalogs security considerations for the operational and technical aspects of deploying systems that rely on Stateful HBS. Management of the state of the Stateful HBS, including any handling of redundant key material, is a sensitive topic. This document describes some approaches to handle the associated challenges. It also describes the challenges that need to be resolved before certain approaches should be considered.

This document extends HSS/LMS (RFC 8554) by defining parameter sets that use alternative hash functions. These include hash functions that result in signatures with significantly smaller sizes than the signatures that use the RFC 8554 parameter sets and should have sufficient security.

This document is a product of the Internet Research Task Force (IRTF). The IRTF publishes the results of Internet-related research and development activities. These results might not be suitable for deployment. This RFC represents the consensus of the Crypto Forum Research Group of the Internet Research Task Force (IRTF). Documents approved for publication by the IRSG are not candidates for any level of Internet Standard; see Section 2 of RFC 7841.

This document specifies algorithm identifiers and ASN.1 encoding formats for the following stateful Hash-Based Signature (HBS) schemes: Hierarchical Signature System (HSS), eXtended Merkle Signature Scheme (XMSS), and XMSS^MT (a multi-tree variant of XMSS). This specification applies to the Internet X.509 Public Key Infrastructure (PKI) when digital signatures are used to sign certificates and certificate revocation lists (CRLs).

This document specifies the conventions for using the Hierarchical Signature System (HSS) / Leighton-Micali Signature (LMS) hash-based signature algorithm with the Cryptographic Message Syntax (CMS). In addition, the algorithm identifier and public key syntax are provided. The HSS/LMS algorithm is one form of hash-based digital signature; it is described in RFC 8554. This document obsoletes RFC 8708.

Concise Binary Object Representation (CBOR) is a data format designed for small code size and small message size. There is a need to be able to define basic security services for this data format. This document defines a set of algorithms that can be used with the CBOR Object Signing and Encryption (COSE) protocol (RFC 9052).

This document, along with RFC 9052, obsoletes RFC 8152.

This document specifies the conventions for using the Hierarchical Signature System (HSS) / Leighton-Micali Signature (LMS) hash-based signature algorithm with the CBOR Object Signing and Encryption (COSE) syntax. The HSS/LMS algorithm is one form of hash-based digital signature; it is described in RFC 8554.

This note describes a digital-signature system based on cryptographic hash functions, following the seminal work in this area of Lamport, Diffie, Winternitz, and Merkle, as adapted by Leighton and Micali in 1995. It specifies a one-time signature scheme and a general signature scheme. These systems provide asymmetric authentication without using large integer mathematics and can achieve a high security level. They are suitable for compact implementations, are relatively simple to implement, and are naturally resistant to side-channel attacks. Unlike many other signature systems, hash-based signatures would still be secure even if it proves feasible for an attacker to build a quantum computer.

This document is a product of the Crypto Forum Research Group (CFRG) in the IRTF. This has been reviewed by many researchers, both in the research group and outside of it. The Acknowledgements section lists many of them.