KN-Cipher
{{Short description|Block cipher}}
{{Infobox block cipher
| name = KN-Cipher
| designers = Kaisa Nyberg and Lars Knudsen
| publish date = 1995
| derived from =
| derived to =
| related to =
| certification =
| key size = 198 bits
| block size = 64 bits
| structure = Feistel network
| rounds = 6
| cryptanalysis = Jakobsen & Knudsen's higher order differential cryptanalysis breaks KN-Cipher with only 512 chosen plaintexts and 241 running time, or with 32 chosen plaintexts and 270 running time.
}}
In cryptography, KN-Cipher is a block cipher created by Kaisa Nyberg and Lars Knudsen in 1995. One of the first ciphers designed to be provably secure against ordinary differential cryptanalysis, KN-Cipher was later broken using higher order differential cryptanalysis.
Presented as "a prototype...compatible with DES", the algorithm has a 64-bit block size and a 6-round Feistel network structure. The round function is based on the cube operation in the finite field GF(233).
The designers did not specify any key schedule for the cipher; they state, "All round keys should be independent, therefore we need at least 198 key bits."
Cryptanalysis
Jakobsen & Knudsen's higher order differential cryptanalysis breaks KN-Cipher with only 512 chosen plaintexts and 241 running time, or with 32 chosen plaintexts and 270 running time.
References
{{reflist | refs=
{{cite journal | author = K. Nyberg, L.R. Knudsen | title = Provable Security Against a Differential Attack | journal = Journal of Cryptology | volume = 8 | issue = 1 | issn = 0933-2790 | pages = 27–37 | year = 1995 | url = http://citeseer.ist.psu.edu/nyberg95provable.html | format = PDF/PostScript | access-date = 23 January 2007 | doi=10.1007/bf00204800| s2cid = 11867695 | url-access = subscription }}
{{cite conference | author = T. Jakobsen, L.R. Knudsen | title = The Interpolation Attack on Block Ciphers | conference = 4th International Workshop on Fast Software Encryption (FSE '97) | pages = 28–40 | publisher = Springer-Verlag | date = January 1997 | location = Haifa | url = http://citeseer.ist.psu.edu/jakobsen97interpolation.html | format = PDF/PostScript | access-date = 23 January 2007}}
}}
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