Pre-Shared Key (PSK) Ciphersuites with NULL Encryption for Transport Layer Security (TLS)
draft-ietf-tls-psk-null-03

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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