MARS is a block cipher that was IBM's submission to the Advanced Encryption Standard process.
The MARS design team included Don Coppersmith, who had been involved in the creation of the previous Data Encryption Standard (DES) twenty years earlier.
The project was specifically designed to resist future advances in cryptography by adopting a layered, compartmentalized approach.
IBM's official report stated that MARS and Serpent were the only two finalists to implement any form of safety net with regard to would-be advances in cryptographic mathematics.
[3] A meet-in-the-middle attack published in 2004 by John Kelsey and Bruce Schneier can break 21 out of 32 rounds of MARS.