Editing Block cipher (section)

===Lucifer / DES===
{{main|Lucifer (cipher)|Data Encryption Standard}}
[[Lucifer (cipher)|Lucifer]] is generally considered to be the first civilian block cipher, developed at [[IBM]] in the 1970s based on work done by [[Horst Feistel]]. A revised version of the algorithm was adopted as a U.S. government [[Federal Information Processing Standard]]: FIPS PUB 46 [[Data Encryption Standard]] (DES).<ref>[http://csrc.nist.gov/publications/fips/fips46-3/fips46-3.pdf FIPS PUB 46-3 ''Data Encryption Standard (DES)''] (This is the third edition, 1999, but includes historical information in the preliminary section 12.)</ref> It was chosen by the U.S. National Bureau of Standards (NBS) after a public invitation for submissions and some internal changes by [[National Institute of Standards and Technology|NBS]] (and, potentially, the [[NSA]]). DES was publicly released in 1976 and has been widely used.{{citation needed|date=April 2012}}

DES was designed to, among other things, resist a certain cryptanalytic attack known to the NSA and rediscovered by IBM, though unknown publicly until rediscovered again and published by [[Eli Biham]] and [[Adi Shamir]] in the late 1980s. The technique is called [[differential cryptanalysis]] and remains one of the few general attacks against block ciphers; [[linear cryptanalysis]] is another but may have been unknown even to the NSA, prior to its publication by [[Mitsuru Matsui]]. DES prompted a large amount of other work and publications in cryptography and [[cryptanalysis]] in the open community and it inspired many new cipher designs.{{citation needed|date=April 2012}}

DES has a block size of 64 bits and a [[key size]] of 56 bits. 64-bit blocks became common in block cipher designs after DES. Key length depended on several factors, including government regulation. Many observers{{who|date=April 2012}} in the 1970s commented that the 56-bit key length used for DES was too short. As time went on, its inadequacy became apparent, especially after a [[EFF DES cracker|special-purpose machine designed to break DES]] was demonstrated in 1998 by the [[Electronic Frontier Foundation]]. An extension to DES, [[Triple DES]], triple-encrypts each block with either two independent keys (112-bit key and 80-bit security) or three independent keys (168-bit key and 112-bit security). It was widely adopted as a replacement. As of 2011, the three-key version is still considered secure, though the [[National Institute of Standards and Technology]] (NIST) standards no longer permit the use of the two-key version in new applications, due to its 80-bit security level.<ref name="NIST_SP_800-57">[http://csrc.nist.gov/publications/nistpubs/800-57/sp800-57-Part1-revised2_Mar08-2007.pdf NIST Special Publication 800-57 ''Recommendation for Key Management — Part 1: General (Revised)'', March, 2007] {{webarchive|url=https://web.archive.org/web/20140606050814/http://csrc.nist.gov/publications/nistpubs/800-57/sp800-57-Part1-revised2_Mar08-2007.pdf|date=June 6, 2014}}.</ref>