draft-ietf-tls-psk-null-03.txt   rfc4785.txt 
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 Network Working Group U. Blumenthal
Transport Layer Security (TLS) Request for Comments: 4785 P. Goel
Category: Standards Track Intel Corporation
January 2007
draft-ietf-tls-psk-null-03.txt Pre-Shared Key (PSK) Ciphersuites with NULL Encryption for
Transport Layer Security (TLS)
Status of this Memo Status of This Memo
By submitting this Internet-Draft, each author represents that This document specifies an Internet standards track protocol for the
any applicable patent or other IPR claims of which he or she is Internet community, and requests discussion and suggestions for
aware have been or will be disclosed, and any of which he or she improvements. Please refer to the current edition of the "Internet
becomes aware will be disclosed, in accordance with Section 6 of Official Protocol Standards" (STD 1) for the standardization state
BCP 79. and status of this protocol. Distribution of this memo is unlimited.
Internet-Drafts are working documents of the Internet Engineering Copyright Notice
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Copyright (C) The IETF Trust (2007).
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at Abstract
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at This document specifies authentication-only ciphersuites (with no
http://www.ietf.org/shadow.html 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.
This Internet-Draft will expire on April 20, 2007. Table of Contents
Abstract 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
This document specifies authentication-only cipher suites (with no 1. Introduction
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.
Internet-Draft PSK NULL-encryption Cipher Suites for TLS October The RFC for Pre-Shared Key (PSK) based Transport Layer Security (TLS)
2006 [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.
Conventions used in this document 1.1. Applicability Statement
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The ciphersuites defined in this document are intended for a rather
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this limited set of applications, usually involving only a very small
document are to be interpreted as described in [RFC2119]. number of clients and servers. Even in such environments, other
alternatives may be more appropriate.
Table of Contents 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.
1. Introduction...................................................2 It is also possible to use the Secure Remote Password (SRP)
2. Cipher Usage...................................................2 ciphersuites for shared secret authentication [SRP]. SRP was
3. Security Considerations........................................3 designed to be used with passwords, and it incorporates protection
4. IANA Considerations............................................3 against dictionary attacks. However, it is computationally more
5. Acknowledgments................................................3 expensive than the PSK ciphersuites in [TLS-PSK].
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 2. Conventions Used in This Document
The RFC for Pre-Shared Key based TLS [TLS-PSK] specifies cipher The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
suites for supporting TLS using pre-shared symmetric keys. However "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
all the cipher suites defined in [TLS-PSK] require encryption. document are to be interpreted as described in [RFC2119].
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 3. Cipher Usage
The three new cipher suites proposed here match the three cipher The three new cipher suites proposed here match the three cipher
suites defined in [TLS-PSK], except that we define suites with null suites defined in [TLS-PSK], except that we define suites with null
encryption. encryption.
Internet-Draft PSK NULL-encryption Cipher Suites for TLS October
2006
The cipher suites defined here use the following options for key The cipher suites defined here use the following options for key
exchange and hash part of the protocol: exchange and hash part of the protocol:
CipherSuite Key Exchange Cipher Hash CipherSuite Key Exchange Cipher Hash
TLS_PSK_WITH_NULL_SHA PSK NULL SHA TLS_PSK_WITH_NULL_SHA PSK NULL SHA
TLS_DHE_PSK_WITH_NULL_SHA DHE_PSK NULL SHA TLS_DHE_PSK_WITH_NULL_SHA DHE_PSK NULL SHA
TLS_RSA_PSK_WITH_NULL_SHA RSA_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- 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 PSK]. For the meaning of the terms DHE, RSA, and SHA, please refer
sections A.5 and Appendix B in [TLS]. to appendixes A.5 and B in [TLS].
3. Security Considerations 4. Security Considerations
As with all schemes involving shared keys, special care should be As with all schemes involving shared keys, special care should be
taken to protect the shared values and to limit their exposure over taken to protect the shared values and to limit their exposure over
time. As this document augments [TLS-PSK], everything stated in its time. As this document augments [TLS-PSK], everything stated in its
Security Consideration section applies here. In addition, as cipher Security Consideration section applies here. In addition, as cipher
suites defined here do not support confidentiality - care should be suites defined here do not support confidentiality, care should be
taken not to send sensitive information (such as passwords) over taken not to send sensitive information (such as passwords) over
connection protected with one of the cipher suites defined in this connections protected with one of the ciphersuites defined in this
document. document.
4. IANA Considerations 5. IANA Considerations
This document defines three new cipher suites, whose values are to be This document defines three new ciphersuites whose values are in the
assigned from the TLS Cipher Suite registry defined in [TLS]. TLS Cipher Suite registry defined in [TLS].
CipherSuite TLS_PSK_WITH_NULL_SHA = { 0x00, 0xTBD1 }; CipherSuite TLS_PSK_WITH_NULL_SHA = { 0x00, 0x2C };
CipherSuite TLS_DHE_PSK_WITH_NULL_SHA = { 0x00, 0xTBD2 }; CipherSuite TLS_DHE_PSK_WITH_NULL_SHA = { 0x00, 0x2D };
CipherSuite TLS_RSA_PSK_WITH_NULL_SHA = { 0x00, 0xTBD3 }; CipherSuite TLS_RSA_PSK_WITH_NULL_SHA = { 0x00, 0x2E };
5. Acknowledgments 6. Acknowledgments
The cipher suites defined in this document are an augmentation to and The cipher suites defined in this document are an augmentation to and
based on [TLS-PSK]. based on [TLS-PSK].
Internet-Draft PSK NULL-encryption Cipher Suites for TLS October 7. References
2006
6. References
6.1. Normative References 7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[TLS] Dierks, T. and Rescorla, E., "The TLS Protocol Version [TLS] Dierks, T. and E. Rescorla, "The Transport Layer Security
1.1", RFC 4346, April 2006. (TLS) Protocol Version 1.1", RFC 4346, April 2006.
[TLS-PSK] Eronen, P., Tschofenig, H., "Pre-Shared Key CipherSuites [TLS-PSK] Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites
for Transport Layer Security (TLS)", RFC 4279, December for Transport Layer Security (TLS)", RFC 4279, December
2005. 2005.
Author's Addresses 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 Uri Blumenthal
Intel Corporation Intel Corporation
1515 State Route 10, 1515 State Route 10,
PY2-1 10-4 PY2-1 10-4
Parsippany, NJ 07054 Parsippany, NJ 07054
USA USA
Email: Uri.Blumenthal@intel.com EMail: urimobile@optonline.net
Purushottam Goel Purushottam Goel
Intel Corporation Intel Corporation
2111 N.E. 25 Ave. 2111 N.E. 25 Ave.
JF3-414 JF3-414
Hillsboro, OR 97124 Hillsboro, OR 97124
USA USA
Email: Purushottam.Goel@intel.com EMail: Purushottam.Goel@intel.com
Acknowledgment Full Copyright Statement
Funding for the RFC Editor function is currently provided by the Copyright (C) The IETF Trust (2007).
Internet Society.
Internet-Draft PSK NULL-encryption Cipher Suites for TLS October This document is subject to the rights, licenses and restrictions
2006 contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
Intellectual Property Statement This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
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skipping to change at page 5, line 32 skipping to change at page 5, line 45
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Disclaimer of Validity Acknowledgement
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2006).
This document is subject to the rights, licenses and restrictions Funding for the RFC Editor function is currently provided by the
contained in BCP 78, and except as set forth therein, the authors Internet Society.
retain all their rights.
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