TLS Working Group U. Blumenthal
Internet Draft P. Goel
Expires: April 2007 Intel Corporation
October 20, 2006
Pre-Shared Key Cipher Suites with NULL Encryption for
Transport Layer Security (TLS)
draft-ietf-tls-psk-null-03.txt
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Abstract
This document specifies authentication-only cipher suites (with no
encryption) for the Pre-Shared Key based Transport Layer Security
(TLS) protocol. These cipher suites are useful when authentication
and integrity protection is desired, but confidentiality is not
needed or not permitted.
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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].
Table of Contents
1. Introduction...................................................2
2. Cipher Usage...................................................2
3. Security Considerations........................................3
4. IANA Considerations............................................3
5. Acknowledgments................................................3
6. References.....................................................4
6.1. Normative References......................................4
Author's Addresses................................................4
Intellectual Property Statement...................................5
Disclaimer of Validity............................................5
Copyright Statement...............................................5
Acknowledgment....................................................4
1. Introduction
The RFC for Pre-Shared Key based TLS [TLS-PSK] specifies cipher
suites for supporting TLS using pre-shared symmetric keys. However
all the cipher suites 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 cipher suites support
authentication of the client and server to each other, and message
integrity. This document augments [TLS-PSK] by adding three more
cipher suites (PSK, DHE_PSK, RSA_PSK) with authentication and
integrity only - no encryption. The reader is expected to become
familiar with [TLS-PSK] standard prior to studying this document.
2. Cipher Usage
The three new cipher suites proposed here match the three cipher
suites defined in [TLS-PSK], except that we define suites with null
encryption.
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The cipher suites defined here use the following options for key
exchange and hash part of the protocol:
CipherSuite Key Exchange Cipher Hash
TLS_PSK_WITH_NULL_SHA PSK NULL SHA
TLS_DHE_PSK_WITH_NULL_SHA DHE_PSK NULL SHA
TLS_RSA_PSK_WITH_NULL_SHA RSA_PSK NULL SHA
For the meaning of the terms PSK please refer to section 1 in [TLS-
PSK]. For the meaning of the terms DHE, RSA and SHA please refer to
sections A.5 and Appendix B in [TLS].
3. Security Considerations
As with all schemes involving shared keys, special care should be
taken to protect the shared values and to limit their exposure over
time. As this document augments [TLS-PSK], everything stated in its
Security Consideration section applies here. In addition, as cipher
suites defined here do not support confidentiality - care should be
taken not to send sensitive information (such as passwords) over
connection protected with one of the cipher suites defined in this
document.
4. IANA Considerations
This document defines three new cipher suites, whose values are to be
assigned from the TLS Cipher Suite registry defined in [TLS].
CipherSuite TLS_PSK_WITH_NULL_SHA = { 0x00, 0xTBD1 };
CipherSuite TLS_DHE_PSK_WITH_NULL_SHA = { 0x00, 0xTBD2 };
CipherSuite TLS_RSA_PSK_WITH_NULL_SHA = { 0x00, 0xTBD3 };
5. Acknowledgments
The cipher suites defined in this document are an augmentation to and
based on [TLS-PSK].
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6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[TLS] Dierks, T. and Rescorla, E., "The TLS Protocol Version
1.1", RFC 4346, April 2006.
[TLS-PSK] Eronen, P., Tschofenig, H., "Pre-Shared Key CipherSuites
for Transport Layer Security (TLS)", RFC 4279, December
2005.
Author's Addresses
Uri Blumenthal
Intel Corporation
1515 State Route 10,
PY2-1 10-4
Parsippany, NJ 07054
USA
Email: Uri.Blumenthal@intel.com
Purushottam Goel
Intel Corporation
2111 N.E. 25 Ave.
JF3-414
Hillsboro, OR 97124
USA
Email: Purushottam.Goel@intel.com
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
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