Pre-Shared Key (PSK) Ciphersuites with NULL Encryption for Transport Layer Security (TLS)
RFC 4785
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RFC - Proposed Standard
(January 2007; No errata)
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2015-10-14
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IETF
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RFC 4785 (Proposed Standard)
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Russ Housley
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Network Working Group U. Blumenthal
Request for Comments: 4785 P. Goel
Category: Standards Track Intel Corporation
January 2007
Pre-Shared Key (PSK) Ciphersuites with NULL Encryption for
Transport Layer Security (TLS)
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document specifies authentication-only ciphersuites (with no
encryption) for the Pre-Shared Key (PSK) based Transport Layer
Security (TLS) protocol. These ciphersuites are useful when
authentication and integrity protection is desired, but
confidentiality is not needed or not permitted.
Table of Contents
1. Introduction ....................................................2
1.1. Applicability Statement ....................................2
2. Conventions Used in This Document ...............................2
3. Cipher Usage ....................................................3
4. Security Considerations .........................................3
5. IANA Considerations .............................................3
6. Acknowledgments .................................................3
7. References ......................................................4
7.1. Normative References .......................................4
7.2. Informative References .....................................4
Blumenthal & Goel Standards Track [Page 1]
RFC 4785 PSK NULL Encryption Ciphersuites for TLS January 2007
1. Introduction
The RFC for Pre-Shared Key (PSK) based Transport Layer Security (TLS)
[TLS-PSK] specifies ciphersuites for supporting TLS using pre-shared
symmetric keys. However, all the ciphersuites defined in [TLS-PSK]
require encryption. However there are cases when only authentication
and integrity protection is required, and confidentiality is not
needed. There are also cases when confidentiality is not permitted -
e.g., for implementations that must meet import restrictions in some
countries. Even though no encryption is used, these ciphersuites
support authentication of the client and server to each other, and
message integrity. This document augments [TLS-PSK] by adding three
more ciphersuites (PSK, DHE_PSK, RSA_PSK) with authentication and
integrity only - no encryption. The reader is expected to become
familiar with [TLS-PSK] standards prior to studying this document.
1.1. Applicability Statement
The ciphersuites defined in this document are intended for a rather
limited set of applications, usually involving only a very small
number of clients and servers. Even in such environments, other
alternatives may be more appropriate.
If the main goal is to avoid Public-key Infrastructures (PKIs),
another possibility worth considering is using self-signed
certificates with public key fingerprints. Instead of manually
configuring a shared secret in, for instance, some configuration
file, a fingerprint (hash) of the other party's public key (or
certificate) could be placed there instead.
It is also possible to use the Secure Remote Password (SRP)
ciphersuites for shared secret authentication [SRP]. SRP was
designed to be used with passwords, and it incorporates protection
against dictionary attacks. However, it is computationally more
expensive than the PSK ciphersuites in [TLS-PSK].
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Blumenthal & Goel Standards Track [Page 2]
RFC 4785 PSK NULL Encryption Ciphersuites for TLS January 2007
3. Cipher Usage
The three new ciphersuites proposed here match the three cipher
suites defined in [TLS-PSK], except that we define suites with null
encryption.
The ciphersuites defined here use the following options for key
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