cryptography Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...

, Nimbus is a

block cipher In cryptography, a block cipher is a deterministic algorithm operating on fixed-length groups of bits, called ''blocks''. Block ciphers are specified cryptographic primitive, elementary components in the design of many cryptographic protocols and ...

invented by Alexis Machado in 2000. It was submitted to the

NESSIE NESSIE (New European Schemes for Signatures, Integrity and Encryption) was a European research project funded from 2000 to 2003 to identify secure cryptographic primitives. The project was comparable to the NIST AES process and the Japanese Gov ...

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

XOR Exclusive or or exclusive disjunction is a logical operation that is true if and only if its arguments differ (one is true, the other is false). It is symbolized by the prefix operator J and by the infix operators XOR ( or ), EOR, EXOR, , ...

ed 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 Vladimir may refer to: Names * Vladimir (name) for the Bulgarian, Croatian, Czech, Macedonian, Romanian, Russian, Serbian, Slovak and Slovenian spellings of a Slavic name * Uladzimir for the Belarusian version of the name * Volodymyr for the Ukr ...

; he found a

differential attack Differential cryptanalysis is a general form of cryptanalysis applicable primarily to block ciphers, but also to stream ciphers and cryptographic hash functions. In the broadest sense, it is the study of how differences in information input can af ...

using only 256 chosen plaintexts.

References

Broken block ciphers {{crypto-stub