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Versions: 00                                                            
     Security Working Group                             R. Thayer
     Internet Draft                                     June 1997
     Expire in six months
     
                          The ESP ARCFOUR Algorithm
                       <draft-ietf-ipsec-ciph-arcfour-00.txt>
     
     Status of This Memo
     
     This document is a submission to the IETF Internet Protocol
     Security (IPSEC) Working Group. Comments are solicited and should
     be addressed to the working group mailing list (ipsec@tis.com) or
     to the editor.
     
     This document is an Internet-Draft.  Internet Drafts are working
     documents of the Internet Engineering Task Force (IETF), its areas,
     and its working Groups. Note that other groups may also distribute
     working documents as Internet Drafts.
     
     Internet-Drafts draft documents are valid for a maximum of six
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     Distribution of this memo is unlimited.
     
     Abstract
     
     This draft describes the use of the ARCFOUR [Kaukonen] stream
     cipher algorithm to be used with the IPSec Encapsulating Security
     Payload [ESP].
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     Thayer                                              Page [1]
     
     
     
     
     Internet Draft   The ESP ARCFOUR Algorithm         June 1997
     
     
     
     Contents
     
     
     STATUS OF THIS MEMO...............................................1
     
     
     ABSTRACT..........................................................1
     
     
     CONTENTS..........................................................2
     
     
     1. INTRODUCTION...................................................2
     
      1.1 SPECIFICATION OF REQUIREMENTS ...............................3
     
     2. CIPHER ALGORITHM...............................................3
     
     
     3. CIPHER KEY SPECIFICATIONS......................................3
     
     
     4. ESP PAYLOAD....................................................3
     
     
     5. SECURITY CONSIDERATIONS........................................3
     
     
     6. ACKNOWLEDEMENTS................................................3
     
     
     7. REFERENCES.....................................................4
     
     
     8. EDITOR'S ADDRESS...............................................4
     
     
     1. Introduction
     
     This draft describes the use of the ARCFOUR stream algorithm to
     provide confidentiality in conjunction with the IPsec ESP protocol
     [ESP].
     
     This document assumes readers with the terms and concepts in [RFC-
     1825] and in [ESP].  This document follows the IPsec document
     framework described in [Framework].
     
     ARCFOUR is described in detail in [Kaukonen].
     
     
     Thayer                                              [Page 2]


     Internet Draft   The ESP ARCFOUR Algorithm         June 1997
     
     
     1.1 Specification of Requirements
     Interpret the keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD",
     "SHOULD NOT", and "MAY" that appear in this document as described
     in [RFC-2119].
     
     2. Cipher Algorithm
     
     The cipher algorithm specified in this document is the ARCFOUR
     stream cipher.
     
     Hardware implementations of this algorithm are expected to perform
     in the 5-20 megabyte per second range.
     
     3. Cipher Key Specifications
     
     The keys used with this cipher for ESP SHOULD be either 40 or 128
     bits.  All implementations must support 40 bit keys. All
     implementations SHOULD support 128 bit keys.  The use of 40 bit
     keys SHOULD be limited due to known attacks against this algorithm
     with that key length.
     
     The keying material passed from key management MUST be either 40
     bits or 128 bits of key, passed as 5 or 16 bytes.
     
     4. ESP Payload
     
     The ESP packet payload contains only the actual payload data.  No
     IV is required for this cipher.
     
     5. Security Considerations
     
     40 bit keys for ARCFOUR have been shown to be breakable.  128 bit
     keys should be used.  40 bit keys should only be used for
     exportable demonstration implementations.
     
     As with any other encryption technology, one should examine the
     current literature for any new attack strategies discovered after
     this document was published.
     
     6. Acknowledements
     
     An earlier draft discussing the use of this cipher was published in
     1996 by Caronni and Waldvogel, "The ESP Stream Transform", draft-
     caronni-esp-stream-01.txt, September, 1996.
     
     The ARCFOUR algorithm is described in [Schneier] and in the
     Internet Draft draft-ietf-cipher-arcfour-00.txt soon to be
     submitted by Kaukonen and Thayer.
     
     
     
     Thayer                                              [Page 3]


     Internet Draft   The ESP ARCFOUR Algorithm         June 1997
     
     
     The ESP protocol is more recently discussed in draft-ietf-ipsec-
     esp-04.txt.
     
     The IPsec document framework is described in draft-ietf-doc-
     roadmap-00.txt.
     
     7. References
     
     [ESP] Atkinson, R., "IP Encapsulating Security Protocol (ESP)",
     Naval Research Laboratory, July 1995.
     
     [Framework] The IP Security Document Roadmap, RFC-xxxx.
     
     [Kaukonen] The ARCFOUR Stream Cipher, RFC-xxxx.
     
     [RFC-2119] Bradner, S., "Key words for use in RFCs to indicate
     Requirement Levels", ftp://ds.internic.net/rfc/rfc2119.txt, March
     1997
     
     [Schneier] Schneier, B., "Applied Cryptography Second Edition",
     John Wiley & Sons, New York, NY, 1995.  ISBN 0-471-12845-7
     
     8. Editor's Address
     
     Rodney Thayer
     Sable Technology Corporation
     246 Walnut Street
     Newton, Massachusetts U.S.A.
     617 332 7292
     Fax 617 332 7970
     <mailto: rodney@sabletech.com>
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     Thayer                                              [Page 4]