Q (cipher)
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| Designer(s): | Leslie McBride |
|---|---|
| First published: | 2000-11 |
| Derived from: | AES, Serpent |
| Key size(s): | 128, 192, or 256 bits |
| Block size(s): | 128 bits |
| Structure: | Substitution-permutation network |
| Rounds: | 8 or 9 |
| Best public cryptanalysis: | |
| A linear attack succeeds with 98.4% probability using 297 known plaintexts.[1] | |
In cryptography, Q is a block cipher invented by Leslie McBride. It was submitted to the NESSIE project, but was not selected.
The algorithm uses a key size of 128, 192, or 256 bits. It operates on blocks of 128 bits using a substitution-permutation network structure. There are 8 rounds for a 128-bit key and 9 rounds for a longer key. Q uses S-boxes adapted from Rijndael (also known as AES) and Serpent. It combines the nonlinear operations from these ciphers, but leaves out all the linear transformations except the permutation.[2] Q also uses a constant derived from the golden ratio as a source of "nothing up my sleeve numbers".
Q is theoretically vulnerable to linear cryptanalysis; Keliher, Meijer, and Tavares have an attack that succeeds with 98.4% probability using 297 known plaintexts.[1]
[edit] References
- ^ a b L. Keliher, H. Meijer, and S. Tavares (2001-09-12). "High probability linear hulls in Q" (PDF/PostScript). Proceedings of Second Open NESSIE Workshop. Retrieved on 2006-12-16.
- ^ Eli Biham, Vladimir Furman, Michal Misztal, Vincent Rijmen (2001-02-11). "Differential Cryptanalysis of Q" (PDF/PostScript). 8th International Workshop on Fast Software Encryption (FSE 2001): 174-186, Yokohama: Springer-Verlag. Retrieved on 2006-12-26.
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