Use of RSA Keys with SHA-256 and SHA-512 in the Secure Shell (SSH) Protocol
RFC 8332
Internet Engineering Task Force (IETF) D. Bider
Request for Comments: 8332 Bitvise Limited
Updates: 4252, 4253 March 2018
Category: Standards Track
ISSN: 2070-1721
Use of RSA Keys with SHA-256 and SHA-512
in the Secure Shell (SSH) Protocol
Abstract
This memo updates RFCs 4252 and 4253 to define new public key
algorithms for use of RSA keys with SHA-256 and SHA-512 for server
and client authentication in SSH connections.
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/rfc8332.
Bider Standards Track [Page 1]
RFC 8332 Use of RSA Keys with SHA-256 and SHA-512 March 2018
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Table of Contents
1. Overview and Rationale . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Terminology . . . . . . . . . . . . . . . . 3
1.2. Wire Encoding Terminology . . . . . . . . . . . . . . . . 3
2. Public Key Format vs. Public Key Algorithm . . . . . . . . . 3
3. New RSA Public Key Algorithms . . . . . . . . . . . . . . . . 4
3.1. Use for Server Authentication . . . . . . . . . . . . . . 5
3.2. Use for Client Authentication . . . . . . . . . . . . . . 5
3.3. Discovery of Public Key Algorithms Supported by Servers . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5.1. Key Size and Signature Hash . . . . . . . . . . . . . . . 7
5.2. Transition . . . . . . . . . . . . . . . . . . . . . . . 7
5.3. PKCS #1 v1.5 Padding and Signature Verification . . . . . 7
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. Normative References . . . . . . . . . . . . . . . . . . 8
6.2. Informative References . . . . . . . . . . . . . . . . . 8
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
Bider Standards Track [Page 2]
RFC 8332 Use of RSA Keys with SHA-256 and SHA-512 March 2018
1. Overview and Rationale
Secure Shell (SSH) is a common protocol for secure communication on
the Internet. In [RFC4253], SSH originally defined the public key
algorithms "ssh-rsa" for server and client authentication using RSA
with SHA-1, and "ssh-dss" using 1024-bit DSA and SHA-1. These
algorithms are now considered deficient. For US government use, NIST
has disallowed 1024-bit RSA and DSA, and use of SHA-1 for signing
[NIST.800-131A].
This memo updates RFCs 4252 and 4253 to define new public key
algorithms allowing for interoperable use of existing and new RSA
keys with SHA-256 and SHA-512.
1.1. Requirements Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
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