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Transport Layer Security Working Group John Banes
INTERNET-DRAFT Microsoft Corporation
Expires January, 2002 Richard Harrington
Qpass Incorporated
July 19, 2001
56-bit Export Cipher Suites For TLS
draft-ietf-tls-56-bit-ciphersuites-01.txt
1. Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of Section 10 of RFC2026. 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 are draft documents valid for a maximum of six months
and may be updated, replaced, or made obsolete by other documents at
any time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
2. Introduction
This document describes several cipher suites to be used with the
Transport Layer Security (TLS) protocol. Changes in US export
regulations in 1999 permitted the export of software programs
using 56-bit data encryption and 1024-bit key exchange.
The cipher suites described in this document were designed to take
advantage of this change in the regulations.
3. The CipherSuites
The following values define the CipherSuite codes used in the client
hello and server hello messages.
The following CipherSuite definitions require that the server
provide an RSA certificate that can be used for key exchange. The
server may request either an RSA or a DSS signature-capable
certificate in the certificate request message.
CipherSuite TLS_RSA_EXPORT1024_WITH_DES_CBC_SHA = { 0x00,0x62 };
CipherSuite TLS_RSA_EXPORT1024_WITH_RC4_56_SHA = { 0x00,0x64 };
Banes Expires January, 2002 [Page 1]
INTERNET-DRAFT 56-bit Export TLS January 15, 1999
The following CipherSuite definitions are used for
server-authenticated (and optionally client-authenticated)
Diffie-Hellman. DHE denotes ephemeral Diffie-Hellman, where the
Diffie-Hellman parameters are signed by a DSS certificate, which
has been signed by the CA.
CipherSuite TLS_DHE_DSS_EXPORT1024_WITH_DES_CBC_SHA = { 0x00,0x63 };
CipherSuite TLS_DHE_DSS_EXPORT1024_WITH_RC4_56_SHA = { 0x00,0x65 };
CipherSuite TLS_DHE_DSS_WITH_RC4_128_SHA = { 0x00,0x66 };
4. CipherSuite definitions
CipherSuite Is Key Cipher Hash
Exportable Exchange
TLS_RSA_EXPORT1024_WITH_DES_CBC_SHA * RSA_EXPORT1024 DES_CBC SHA
TLS_RSA_EXPORT1024_WITH_RC4_56_SHA * RSA_EXPORT1024 RC4_56 SHA
TLS_DHE_DSS_EXPORT1024_WITH_DES_CBC_SHA * RSA_EXPORT1024 DES_CBC SHA
TLS_DHE_DSS_EXPORT1024_WITH_RC4_56_SHA * DHE_DSS_EXPORT1024 RC4_56 SHA
TLS_DHE_DSS_WITH_RC4_128_SHA DHE_DSS RC4_128 SHA
* Indicates IsExportable is True
Key
Exchange
Algorithm Description Key size limit
RSA_EXPORT1024 RSA key exchange RSA = 1024 bits
DHE_DSS_EXPORT1024 Ephemeral DH with DSS signatures DH = 1024 bits
Key size limit
The key size limit gives the size of the largest public key that
can be legally used for encryption in cipher suites that are
exportable.
Key Expanded Effective IV Block
Cipher Type Material Key Material Key Bits Size Size
RC4_56 Stream 7 16 56 0 N/A
DES_CBC Block 8 8 56 8 8
5. Implementation Notes
When an RSA_EXPORT1024 cipher suite is used, and the server's RSA
Key is larger than 1024 bits in length, then the server must send
a server key exchange message to the client. This message is to
contain a temporary RSA key, signed by the server. This temporary
RSA key should be the maximum allowable length (i.e., 1024 bits).
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INTERNET-DRAFT 56-bit Export TLS January 15, 1999
Servers with a large RSA key will often maintain two temporary RSA
keys: a 512-bit key used to support the RSA_EXPORT cipher suites,
and a 1024-bit key used to support the RSA_EXPORT1024 cipher suites.
When 56-bit DES keys are derived for an export cipher suite, the
additional export key derivation step must be performed. That is,
the final read and write DES keys (and the IV) are not taken
directly from the key_block.
6. References
[TLS] T. Dierks, C. Allen, The TLS Protocol,
<draft-ietf-tls-protocol-06.txt>, November 1998.
7. Authors
John Banes Richard Harrington
Microsoft Corp. Qpass Inc.
jbanes@microsoft.com rharrington@qpass.com
Banes Expires January, 2002 [Page 3]
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