MacGuffin (cryptology)

For more information on the concept of MacGuffin, you with the principal article refer.

MacGuffin is a symmetrical algorithm of Chiffrement invented by Bruce Schneier and Matt Blaze in 1994 during the session Fast Software Encryption . This algorithm acted as testing ground for a new structure in cryptography, the diagrams of Feistel not-balanced. The Cryptanalyse was very quickly carried out by Vincent Rijmen and Bart Preneel which broke MacGuffin during the Fast Software Encryption .

Algorithm

Based on OF the, MacGuffin does not divide the data into two equal blocks in the diagram of Feistel. A block of 48 bits (among 64 bits of data) is sent in a function after a XOR with an intermediate key. One carries out then a XOR between the exit of the function and the remainder of the 16 bits. The result is transmitted to the following stage of the diagram of Feistel. The originators recommended a Taille of key of 128 bits.

Cryptanalyse

A analyzes differential by Rijmen and Preneel quickly highlighted vulnerabilities. The 32 rounds advised by Schneier proved weaker than 16 rounds of DES. It took indeed only “few hours” to obtain good differential characteristics starting from unspecified initial values (contrary to which requires good initial values). The two cryptologists showed that it was possible to obtain the last under-key in the diagram of Feistel and to proceed step by step to recover the remainder of the keys.

References

B. Schneier and Mr. Blaze, “MacGuffin: year unbalanced Feistel network block cipher”, Fast Encryption Software, Second International Workshop Proceedings (December 1994), Springer-Verlag, 1995, pp. 97-110.
V. Rijmen and B. Preneel, “Cryptanalysis off McGuffin”, Fast Encryption Software, Second International Workshop Proceedings (December 1994)

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