Network Working Group P. Eronen, Ed.
Request for Comments: 5469 Nokia
Category: Informational February 2009
DES and IDEA Cipher Suites for Transport Layer Security (TLS)
1. Introduction
TLS versions 1.0 [TLS10] and 1.1 [TLS11] include cipher suites based on DES (Data Encryption Standard) and IDEA (International Data Encryption Algorithm) algorithms. DES (when used in single-DES mode) and IDEA are no longer recommended for general use in TLS, and have been removed from TLS version 1.2 [TLS12].
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RFC 5469 DES and IDEA Cipher Suites for TLS February 2009 2. DES Cipher SuitesDES (Data Encryption Standard) is a block cipher that was originally approved as a US federal standard in 1976, and is specified in [DES].
3. IDEA Cipher Suite
IDEA (International Data Encryption Algorithm) is a block cipher designed by Xuejia Lai and James Massey [IDEA] [SCH]. IDEA uses a 128-bit key and operates on 64-bit blocks.4. Security Considerations 4.1. DES Cipher SuitesDES has an effective key strength of 56 bits, which has been known to be vulnerable to practical brute force attacks for over 20 years [DH]. A relatively recent 2006 paper by Kumar, et al. [COPA] describes a system that performs an exhaustive key search in less than nine days on average, and costs less than 10,000 USD to build. Given this, the single-DES cipher suites SHOULD NOT be implemented by TLS libraries. If a TLS library implements these cipher suites, it SHOULD NOT enable them by default. Experience has also shown that rarely used code is a source of security and interoperability problems, so existing implementations SHOULD consider removing these cipher suites.
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RFC 5469 DES and IDEA Cipher Suites for TLS February 2009 4.2. IDEA Cipher SuiteIDEA has a 128-bit key, and thus is not vulnerable to an exhaustive key search. However, the IDEA cipher suite for TLS has not seen widespread use: most implementations either do not support it, do not enable it by default, or do not negotiate it when other algorithms (such as AES, 3DES, or RC4) are available.
5. IANA Considerations
IANA has already allocated values for the cipher suites described in this document in the TLS Cipher Suite Registry, defined in [TLS11]. IANA has updated the references of these cipher suites to point to this document:Value Description Reference ----------- -------------------------------------- --------- 0x00,0x07 TLS_RSA_WITH_IDEA_CBC_SHA [RFC5469]0x00,0x09 TLS_RSA_WITH_DES_CBC_SHA [RFC5469] 0x00,0x0C TLS_DH_DSS_WITH_DES_CBC_SHA [RFC5469] 0x00,0x0F TLS_DH_RSA_WITH_DES_CBC_SHA [RFC5469] 0x00,0x12 TLS_DHE_DSS_WITH_DES_CBC_SHA [RFC5469] 0x00,0x15 TLS_DHE_RSA_WITH_DES_CBC_SHA [RFC5469] 0x00,0x1A TLS_DH_anon_WITH_DES_CBC_SHA [RFC5469]
6. Acknowledgments
The editor would like to thank Steven Bellovin, Uri Blumenthal, Michael D'Errico, Paul Hoffman, Simon Josefsson, Bodo Moeller, Tom Petch, Martin Rex, and Len Sassaman for their contributions to preparing this document.
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RFC 5469 DES and IDEA Cipher Suites for TLS February 2009 7. References 7.1. Normative References[DES] National Institute of Standards and Technology, "Data
7.2. Informative References
[COPA] Kumar, S., Paar, C., Pelzl, J., Pfeiffer, G., and M.