ICE (cipher)
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Apokrif
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[[Category:Feistel cipher]]
{{Infobox block cipher
| name = ICE
| image = [[Image:ICE (cipher) InfoBox Diagram.png|280px|center]]
| caption = The ICE Feistel function
| designers = Matthew Kwan
| publish date = 1997
| derived from = [[Data Encryption Standard|DES]]
| derived to =
| key size = 64 bits (ICE), 64×''n'' bits (ICE-''n'')
| block size = 64 bits
| structure = [[Feistel network]]
| rounds = 16 (ICE), 8 (Thin-ICE), 16×''n'' (ICE-''n'')
| cryptanalysis = [[Differential cryptanalysis]] can break 15 out of 16 rounds of ICE with complexity 2<sup>56</sup>. Thin-ICE can be broken using 2<sup>27</sup> chosen plaintexts with a success probability of 95%.
}}
In [[cryptography]], '''ICE (Information Concealment Engine)''' is a [[block cipher]] published by Kwan in 1997. The algorithm is similar in structure to [[Data Encryption Standard|DES]], but with the addition of a key-dependent bit permutation in the round function. The key-dependent bit permutation is implemented efficiently in software. The ICE algorithm is not subject to patents, and the source code has been placed into the public domain.
ICE is a [[Feistel network]] with a [[block size (cryptography)|block size]] of 64 bits. The standard ICE algorithm takes a 64-bit key and has 16 rounds. A fast variant, '''Thin-ICE''', uses only 8 rounds. An open-ended variant, '''ICE-''n''''', uses 16''n'' rounds with 64''n'' bit key.
Van Rompay et al (1998) attempted to apply [[differential cryptanalysis]] to ICE. They described an attack on Thin-ICE which recovers the secret key using 2<sup>23</sup> [[chosen plaintext]]s with a 25% success probability. If 2<sup>27</sup> chosen plaintexts are used, the probability can be improved to 95%. For the standard version of ICE, an attack on 15 out of 16 rounds was found, requiring 2<sup>56</sup> work and at most 2<sup>56</sup> chosen plaintexts.
==References==
* Matthew Kwan, The Design of the ICE Encryption Algorithm, Fast Software Encryption 1997, pp69–82 [http://www.darkside.com.au/ice/paper.html].
* Bart van Rompay, Lars R. Knudsen and Vincent Rijmen, Differential Cryptanalysis of the ICE Encryption Algorithm, Fast Software Encryption 1998, pp270–283 [http://www.cosic.esat.kuleuven.ac.be/publications/article-120.pdf (PDF)].
==External links==
* [http://www.darkside.com.au/ice/index.html The ICE Home Page]
* [http://www.darkside.com.au/ice/slides/slide01.htm The ICE information slides]
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[[Category:Feistel cipher]]
[[fr:ICE (cryptographie)]]