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Transport Layer Security (TLS) Session Hash and Extended Master Secret Extension (RFC7627) Disclosure Number: IPCOM000244959D
Original Publication Date: 2015-Sep-01
Included in the Prior Art Database: 2016-Feb-04
Document File: 30 page(s) / 35K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

K. Bhargavan: AUTHOR [+6]


In TLS [RFC5246], every session has a "master_secret" computed as:

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 8% of the total text.

Internet Engineering Task Force (IETF)                 K. Bhargavan, Ed. Request for Comments: 7627                            A. Delignat-Lavaud Updates: 5246                                                 A. Pironti Category: Standards Track                       Inria Paris-Rocquencourt ISSN: 2070-1721                                               A. Langley                                                              Google Inc.                                                                   M. Ray                                                          Microsoft Corp.                                                           September 2015

             Transport Layer Security (TLS) Session Hash and                     Extended Master Secret Extension


   The Transport Layer Security (TLS) master secret is not    cryptographically bound to important session parameters such as the    server certificate.  Consequently, it is possible for an active    attacker to set up two sessions, one with a client and another with a    server, such that the master secrets on the two sessions are the    same.  Thereafter, any mechanism that relies on the master secret for    authentication, including session resumption, becomes vulnerable to a    man-in-the-middle attack, where the attacker can simply forward    messages back and forth between the client and server.  This    specification defines a TLS extension that contextually binds the    master secret to a log of the full handshake that computes it, thus    preventing such attacks.

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 5741.

   Information about the current status of this document, any errata,    and how to provide feedback on it may be obtained at

Bhargavan, et al.            Standards Track                    [Page 1]
 RFC 7627               TLS Session Hash Extension         September 2015

 Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the    document authors.  All rights reserved.

   This document...