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MARS
 
 
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In cryptography
Cryptography

Cryptography is the practice and study of hiding information. In modern times cryptography is considered a branch of both mathematics and computer science and is affiliated closely with information theory, computer security and engineering....
, MARS is a block cipher
Block cipher

In cryptography, a block cipher is a symmetric key algorithm cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation....
 that was IBM
IBM

International Business Machines Corporation, abbreviated IBM and nicknamed "Big Blue" , is a multinational corporation computer technology and consulting corporation headquartered in Armonk, New York, New York, United States....
's submission to the Advanced Encryption Standard process
Advanced Encryption Standard process

The Advanced Encryption Standard , the block cipher ratified as a standard by National Institute of Standards and Technology of the United States , was chosen using a process markedly more open and transparent than its predecessor, the aging Data Encryption Standard ....
. MARS was selected as an AES finalist in August 1999, after the AES2 conference in March 1999, where it was voted as the fifth and last finalist algorithm.

The MARS design team included Don Coppersmith
Don Coppersmith

Don Coppersmith is a cryptographer and mathematician. He was involved in the design of the Data Encryption Standard block cipher at IBM, particularly the design of the S-box, strengthening them against differential cryptanalysis....
, who had been involved in the creation of the previous Data Encryption Standard
Data Encryption Standard

The Data Encryption Standard is a block cipher that was selected by National Bureau of Standards as an official Federal Information Processing Standard for the United States in 1976 and which has subsequently enjoyed widespread use internationally....
 (DES) twenty years earlier. The project was specifically designed to resist future advances in cryptography by adopting a layered, compartmentalized approach.

IBM
IBM

International Business Machines Corporation, abbreviated IBM and nicknamed "Big Blue" , is a multinational corporation computer technology and consulting corporation headquartered in Armonk, New York, New York, United States....
's official report stated that MARS and Serpent
Serpent (cipher)

Serpent is a symmetric key block cipher which was a finalist in the Advanced Encryption Standard process, where it came second to Rijndael. Serpent was designed by Ross Anderson, Eli Biham, and Lars Knudsen....
 were the only two finalists to implement any form of safety net with regard to would-be advances in cryptographic mathematics.






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In cryptography
Cryptography

Cryptography is the practice and study of hiding information. In modern times cryptography is considered a branch of both mathematics and computer science and is affiliated closely with information theory, computer security and engineering....
, MARS is a block cipher
Block cipher

In cryptography, a block cipher is a symmetric key algorithm cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation....
 that was IBM
IBM

International Business Machines Corporation, abbreviated IBM and nicknamed "Big Blue" , is a multinational corporation computer technology and consulting corporation headquartered in Armonk, New York, New York, United States....
's submission to the Advanced Encryption Standard process
Advanced Encryption Standard process

The Advanced Encryption Standard , the block cipher ratified as a standard by National Institute of Standards and Technology of the United States , was chosen using a process markedly more open and transparent than its predecessor, the aging Data Encryption Standard ....
. MARS was selected as an AES finalist in August 1999, after the AES2 conference in March 1999, where it was voted as the fifth and last finalist algorithm.

The MARS design team included Don Coppersmith
Don Coppersmith

Don Coppersmith is a cryptographer and mathematician. He was involved in the design of the Data Encryption Standard block cipher at IBM, particularly the design of the S-box, strengthening them against differential cryptanalysis....
, who had been involved in the creation of the previous Data Encryption Standard
Data Encryption Standard

The Data Encryption Standard is a block cipher that was selected by National Bureau of Standards as an official Federal Information Processing Standard for the United States in 1976 and which has subsequently enjoyed widespread use internationally....
 (DES) twenty years earlier. The project was specifically designed to resist future advances in cryptography by adopting a layered, compartmentalized approach.

IBM
IBM

International Business Machines Corporation, abbreviated IBM and nicknamed "Big Blue" , is a multinational corporation computer technology and consulting corporation headquartered in Armonk, New York, New York, United States....
's official report stated that MARS and Serpent
Serpent (cipher)

Serpent is a symmetric key block cipher which was a finalist in the Advanced Encryption Standard process, where it came second to Rijndael. Serpent was designed by Ross Anderson, Eli Biham, and Lars Knudsen....
 were the only two finalists to implement any form of safety net with regard to would-be advances in cryptographic mathematics. Interestingly, the Twofish
Twofish

In cryptography, Twofish is a Symmetric-key algorithm block cipher with a block size of 128 bits and key sizes up to 256 bits. It was one of the five finalists of the Advanced Encryption Standard process, but was not selected for standardisation....
 team made a similar statement about its cipher..

MARS has a 128-bit block size
Block size (cryptography)

In modern cryptography, symmetric key algorithm ciphers are generally divided into stream ciphers and block ciphers. Block ciphers operate on a fixed length string of bits....
 and a variable key size
Key size

In cryptography, key size or key length is the size of the key used in a cryptographic algorithm . An algorithm's key length is distinct from its cryptographic security, which is a logarithmic measure of the fastest known computational attack on the algorithm, also measured in bits....
 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
Key whitening

In cryptography, key whitening is a technique intended to increase the security of an block cipher. It consists of steps that combine the data with portions of the key before the first round and after the last round of encryption....
.

Security analysis

Subkeys with long runs of ones or zeroes may lead to efficient attacks on MARS . 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 .

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