Negotiated Finite Field Diffie-Hellman Ephemeral Parameters for Transport Layer Security (TLS)
RFC 7919
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Type |
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RFC - Proposed Standard
(August 2016; No errata)
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Last updated |
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2016-08-10
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Replaces |
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draft-ietf-tls-negotiated-dl-dhe
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Stream |
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IETF
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Formats |
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plain text
pdf
html
bibtex
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WG state
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Submitted to IESG for Publication
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Document shepherd |
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Sean Turner
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Shepherd write-up |
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Show
(last changed 2015-03-16)
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| IESG |
IESG state |
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RFC 7919 (Proposed Standard)
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Consensus Boilerplate |
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Yes
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Telechat date |
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Responsible AD |
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Stephen Farrell
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Send notices to |
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(None)
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| IANA |
IANA review state |
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Version Changed - Review Needed
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IANA action state |
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RFC-Ed-Ack
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Internet Engineering Task Force (IETF) D. Gillmor
Request for Comments: 7919 ACLU
Updates: 2246, 4346, 4492, 5246 August 2016
Category: Standards Track
ISSN: 2070-1721
Negotiated Finite Field Diffie-Hellman Ephemeral Parameters
for Transport Layer Security (TLS)
Abstract
Traditional finite-field-based Diffie-Hellman (DH) key exchange
during the Transport Layer Security (TLS) handshake suffers from a
number of security, interoperability, and efficiency shortcomings.
These shortcomings arise from lack of clarity about which DH group
parameters TLS servers should offer and clients should accept. This
document offers a solution to these shortcomings for compatible peers
by using a section of the TLS "Supported Groups Registry" (renamed
from "EC Named Curve Registry" by this document) to establish common
finite field DH parameters with known structure and a mechanism for
peers to negotiate support for these groups.
This document updates TLS versions 1.0 (RFC 2246), 1.1 (RFC 4346),
and 1.2 (RFC 5246), as well as the TLS Elliptic Curve Cryptography
(ECC) extensions (RFC 4492).
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
http://www.rfc-editor.org/info/rfc7919.
Gillmor Standards Track [Page 1]
RFC 7919 Negotiated FFDHE for TLS August 2016
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Gillmor Standards Track [Page 2]
RFC 7919 Negotiated FFDHE for TLS August 2016
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
1.2. Vocabulary . . . . . . . . . . . . . . . . . . . . . . . 5
2. Named Group Overview . . . . . . . . . . . . . . . . . . . . 5
3. Client Behavior . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Client Local Policy on Custom Groups . . . . . . . . . . 7
4. Server Behavior . . . . . . . . . . . . . . . . . . . . . . . 8
5. Optimizations . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Checking the Peer's Public Key . . . . . . . . . . . . . 9
5.2. Short Exponents . . . . . . . . . . . . . . . . . . . . . 9
5.3. Table Acceleration . . . . . . . . . . . . . . . . . . . 10
6. Operational Considerations . . . . . . . . . . . . . . . . . 10
6.1. Preference Ordering . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8.1. Negotiation Resistance to Active Attacks . . . . . . . . 12
8.2. Group Strength Considerations . . . . . . . . . . . . . . 13
8.3. Finite Field DHE Only . . . . . . . . . . . . . . . . . . 13
8.4. Deprecating Weak Groups . . . . . . . . . . . . . . . . . 14
8.5. Choice of Groups . . . . . . . . . . . . . . . . . . . . 14
8.6. Timing Attacks . . . . . . . . . . . . . . . . . . . . . 14
8.7. Replay Attacks from Non-negotiated FFDHE . . . . . . . . 15
8.8. Forward Secrecy . . . . . . . . . . . . . . . . . . . . . 15
8.9. False Start . . . . . . . . . . . . . . . . . . . . . . . 15
9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16
9.1. Client Fingerprinting . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
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