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Nimbus (cipher)

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DesignersAlexis Machado
First published2000
Cipher detail
Key sizes128 bits
Block sizes64 bits
Best public cryptanalysis
Differential cryptanalysis can break Nimbus with 256 chosen plaintexts.

In cryptography, Nimbus is a block cipher invented by Alexis Machado in 2000. It was submitted to the NESSIE project, but was not selected.

The algorithm uses a 128-bit key. It operates on blocks of 64 bits and consists of 5 rounds of encryption. The round function is exceedingly simple. In each round the block is XORed with a subkey, the order of its bits is reversed, and then it is multiplied mod 264 by another subkey, which is forced to be odd.[1]

Nimbus was broken by Vladimir Furman; he found a differential attack using only 256 chosen plaintexts.[2]


  1. ^ Murphy, Sean; White, Juliette (2001-09-23). "Security Evaluation of NESSIE First Phase: 2.4.6 Nimbus" (PDF). p. 22. Retrieved 2018-09-13.
  2. ^ Eli Biham, Vladimir Furman (2000-11-29). "Differential Cryptanalysis of Nimbus". Fast Software Encryption. Lecture Notes in Computer Science. Vol. 2355. pp. 187–195. doi:10.1007/3-540-45473-X_16. ISBN 978-3-540-45473-1.