Use of the HSS/LMS Hash-Based Signature Algorithm in the Cryptographic Message Syntax (CMS)
RFC 8708
Internet Engineering Task Force (IETF) R. Housley
Request for Comments: 8708 Vigil Security
Category: Standards Track February 2020
ISSN: 2070-1721
Use of the HSS/LMS Hash-Based Signature Algorithm in the Cryptographic
Message Syntax (CMS)
Abstract
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.
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/rfc8708.
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Table of Contents
1. Introduction
1.1. ASN.1
1.2. Terminology
1.3. Motivation
2. HSS/LMS Hash-Based Signature Algorithm Overview
2.1. Hierarchical Signature System (HSS)
2.2. Leighton-Micali Signature (LMS)
2.3. Leighton-Micali One-Time Signature (LM-OTS) Algorithm
3. Algorithm Identifiers and Parameters
4. HSS/LMS Public Key Identifier
5. Signed-Data Conventions
6. Security Considerations
7. IANA Considerations
8. References
8.1. Normative References
8.2. Informative References
Appendix A. ASN.1 Module
Acknowledgements
Author's Address
1. Introduction
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) [CMS]
signed-data content type. The LMS system provides a one-time digital
signature that is a variant of Merkle Tree Signatures (MTS). The HSS
is built on top of the LMS system to efficiently scale for a larger
numbers of signatures. The HSS/LMS algorithm is one form of hash-
based digital signature, and it is described in [HASHSIG]. The HSS/
LMS signature algorithm can only be used for a fixed number of
signing operations with a given private key, and the number of
signing operations depends upon the size of the tree. The HSS/LMS
signature algorithm uses small public keys, and it has low
computational cost; however, the signatures are quite large. The
HSS/LMS private key can be very small when the signer is willing to
perform additional computation at signing time; alternatively, the
private key can consume additional memory and provide a faster
signing time. The HSS/LMS signatures [HASHSIG] are currently defined
to exclusively use SHA-256 [SHS].
1.1. ASN.1
CMS values are generated using ASN.1 [ASN1-B], using the Basic
Encoding Rules (BER) and the Distinguished Encoding Rules (DER)
[ASN1-E].
1.2. 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.
1.3. Motivation
Recent advances in cryptanalysis [BH2013] and progress in the
development of quantum computers [NAS2019] pose a threat to widely
deployed digital signature algorithms. As a result, there is a need
to prepare for a day when cryptosystems such as RSA and DSA that
depend on discrete logarithms and factoring cannot be depended upon.
If large-scale quantum computers are ever built, these computers will
be able to break many of the public key cryptosystems currently in
use. A post-quantum cryptosystem [PQC] is a system that is secure
against quantum computers that have more than a trivial number of
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