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
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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].
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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.
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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>
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