wdiff rfc4785.original rfc4785.txt

TLS
Network Working Group U. Blumenthal
Internet Draft
Request for Comments: 4785 P. Goel
Expires: April 2007
Category: Standards Track Intel Corporation
October 20, 2006
January 2007

Pre-Shared Key Cipher Suites (PSK) Ciphersuites 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 ciphersuites (with no
encryption) for the Pre-Shared Key (PSK) based Transport Layer
Security (TLS) protocol. These cipher suites ciphersuites are useful when
authentication and integrity protection is desired, but
confidentiality is not needed or not permitted.

Internet-Draft PSK NULL-encryption Cipher Suites for TLS October
2006

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 Introduction ....................................................2
1.1. Applicability Statement ....................................2
2. Cipher Usage...................................................2 Conventions Used in This Document ...............................2
3. Security Considerations........................................3 Cipher Usage ....................................................2
4. IANA Considerations............................................3 Security Considerations .........................................3
5. Acknowledgments................................................3 IANA Considerations .............................................3
6. References.....................................................4
6.1. Acknowledgments .................................................3
7. References ......................................................4
7.1. Normative References......................................4
Author's Addresses................................................4
Intellectual Property Statement...................................5
Disclaimer of Validity............................................5
Copyright Statement...............................................5
Acknowledgment....................................................4 References .......................................4
7.2. Informative References .....................................4

1. Introduction

The RFC for Pre-Shared Key (PSK) based TLS Transport Layer Security (TLS)
[TLS-PSK] specifies cipher
suites ciphersuites for supporting TLS using pre-shared
symmetric keys. However However, all the cipher suites 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.
e.g., for implementations that must meet import restrictions in some
countries. Even though no encryption is used, these cipher suites ciphersuites
support authentication of the client and server to each other, and
message integrity. This document augments [TLS-PSK] by adding three
more
cipher suites ciphersuites (PSK, DHE_PSK, RSA_PSK) with authentication and
integrity only - no encryption. The reader is expected to become
familiar with [TLS-PSK] standard 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].

3. Cipher Usage

The three new cipher suites ciphersuites proposed here match the three cipher
suites defined in [TLS-PSK], except that we define suites with null
encryption.

Internet-Draft PSK NULL-encryption Cipher Suites for TLS October
2006

The cipher suites ciphersuites 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 PSK, please refer to section 1 in [TLS-
PSK]. For the meaning of the terms DHE, RSA RSA, and SHA SHA, please refer
to
sections appendixes A.5 and Appendix B in [TLS].

4. 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 - confidentiality, care should be
taken not to send sensitive information (such as passwords) over
connection
connections protected with one of the cipher suites ciphersuites defined in this
document.

5. IANA Considerations

This document defines three new cipher suites, ciphersuites whose values are to be
assigned from in the
TLS Cipher Suite registry defined in [TLS].

CipherSuite TLS_PSK_WITH_NULL_SHA = { 0x00, 0xTBD1 0x2C };
CipherSuite TLS_DHE_PSK_WITH_NULL_SHA = { 0x00, 0xTBD2 0x2D };
CipherSuite TLS_RSA_PSK_WITH_NULL_SHA = { 0x00, 0xTBD3 0x2E };

6. Acknowledgments

The cipher suites ciphersuites defined in this document are an augmentation to and
based on [TLS-PSK].

Internet-Draft PSK NULL-encryption Cipher Suites for TLS October
2006

7. References

6.1.

7.1. 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 E. Rescorla, E., "The TLS Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.

[TLS-PSK] Eronen, P., P. and H. Tschofenig, H., "Pre-Shared Key CipherSuites Ciphersuites
for Transport Layer Security (TLS)", RFC 4279, December
2005.

Author's

7.2. Informative References

[SRP] Taylor, D., Wu, T., Mavrogiannopoulos, N., and T. Perrin,
"Using SRP for TLS Authentication", Work in Progress,
December 2006.

Authors' Addresses

Uri Blumenthal
Intel Corporation
1515 State Route 10,
PY2-1 10-4
Parsippany, NJ 07054
USA

Email: Uri.Blumenthal@intel.com

EMail: urimobile@optonline.net

Purushottam Goel
Intel Corporation
2111 N.E. 25 Ave.
JF3-414
Hillsboro, OR 97124
USA

Email:

EMail: Purushottam.Goel@intel.com

Acknowledgment

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ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
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