Semi-Static Diffie-Hellman Key Establishment for TLS 1.3
draft-ietf-tls-semistatic-dh-00
TLS Working Group E. Rescorla
Internet-Draft Mozilla
Intended status: Standards Track N. Sullivan
Expires: July 20, 2020 Cloudflare
C. Wood
Apple Inc.
January 17, 2020
Semi-Static Diffie-Hellman Key Establishment for TLS 1.3
draft-ietf-tls-semistatic-dh-00
Abstract
TLS 1.3 [I-D.ietf-tls-tls13] specifies a signed Diffie-Hellman
exchange modelled after SIGMA [SIGMA]. This design is suitable for
endpoints whose certified credential is a signing key, which is the
common situation for current TLS servers. This document describes a
mode of TLS 1.3 in which one or both endpoints have a certified DH
key which is used to authenticate the exchange.
Status of This Memo
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This Internet-Draft will expire on July 20, 2020.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 3
3. Negotiation . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Certificate Format . . . . . . . . . . . . . . . . . . . . . 5
5. Cryptographic Details . . . . . . . . . . . . . . . . . . . . 5
5.1. Certificate Verify Computation . . . . . . . . . . . . . 5
5.2. Key Schedule . . . . . . . . . . . . . . . . . . . . . . 6
6. Client Authentication . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
DISCLAIMER: This is a work-in-progress draft and has not yet seen
significant security analysis. Thus, this draft should not be used
as a basis for building production systems.
TLS 1.3 [I-D.ietf-tls-tls13] specifies a signed Diffie-Hellman
exchange modeled after SIGMA [SIGMA]. This design is suitable for
endpoints whose certified credential is a signing key, which is the
common situation for current TLS servers, which is why it was
selected for TLS 1.3.
However, it is also possible - although currently rare - for
endpoints to have a credential which is an (EC)DH key. This can
happen in one of two ways:
o They may be issued a certificate with an (EC)DH key, as specified
for instance in [I-D.ietf-curdle-pkix]
o They may have a signing key which they use to generate a delegated
credential [I-D.ietf-tls-subcerts] containing an (EC)DH key.
In these situations, a signed DH exchange is not appropriate, and
instead a design in which the server authenticates via its long-term
(EC)DH key is suitable. This document describes such a design
modeled on that described in OPTLS [KW16].
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This design has a number of potential advantages over the signed
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