Nimbus (cipher)

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This article is about the block cipher. For other uses, see Nimbus (disambiguation).
Nimbus
General
Designers Alexis Machado
First published 2000
Cipher detail
Key sizes 128 bits
Block sizes 64 bits
Rounds 5
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.

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

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