MARS
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| Designer(s): | IBM |
|---|---|
| First published: | 1998 |
| Certification: | AES finalist |
| Key size(s): | 128, 192, or 256 bits |
| Block size(s): | 128 bits |
| Structure: | Type-3 Feistel network |
| Rounds: | 32 |
In cryptography, MARS is a block cipher which was IBM's submission to the Advanced Encryption Standard process (AES). MARS was selected as an AES finalist; however, it ended up in last place with 13 positive votes and 83 negative votes (for comparison: Rijndael, the winner, got 86 positive votes and 10 negative votes; Serpent, which ended up in 2nd place, got 59 positive votes and 7 negative votes; Twofish, which ended up in 3rd place, got 31 positive votes and 21 negative votes). The design team included Don Coppersmith who had been involved in the creation of the previous Data Encryption Standard (DES) twenty years earlier. It was specifically designed to resist future advances in cryptography by adopting a layered, compartmentalized approach. In IBM's official report, it was stated that MARS and Serpent were the only two finalists to implement any form of safety net with regards to would-be advances in cryptographic mathematics. Nevertheless, the Twofish team made a similar statement about their cipher Twofish, another AES finalist [1].
MARS has a 128-bit block size and a variable key size of between 128 and 448 bits (in 32-bit increments). Unlike most block ciphers, MARS has a heterogeneous structure: several rounds of a cryptographic core are "jacketed" by unkeyed mixing rounds, together with key whitening.
[edit] Security analysis
Subkeys with long runs of ones or zeroes may lead to efficient attacks on MARS [2]. The two least significant bits of round keys used in multiplication are always set to the value 1. Thus, there are always two inputs that are unchanged through the multiplication process regardless of the subkey, and two others which have fixed output regardless of the subkey [2].
[edit] Notes and references
- ^ NIST, Report on the Development of the Advanced Encryption Standard (AES), NIST, 2000.
- ^ a b B. Preneel et al., Comments by the NESSIE Project on the AES Finalists, NIST, 2000.
[edit] External links
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