Explanation of FEAL

Question

Give a brief explanation of the term FEAL.

Answer 1

Fast Data Encipherment Algorithm (or FEAL) was presented by Miyaguchi and Shimizu as an alternative to the DES. The original cipher (as called FEAL-4) was a four-round cryptosystem with the 64-bit block size and the 64-bit key size and it was intended to give high performance in the software. Soon the variety of attacks against FEAL-4 was announced including one attack which needed only 20 chosen plaintexts. Various results in cryptanalysis of FEAL-8 (or eight-round version) led the designers to introduce the revised version, FEAL-N, where N denoted number of rounds. Shamir and Biham developed discrepancy cryptanalytic attacks against FEAL-N for up to 31 rounds. In the year 1994, Ohta and Aoki presented the linear cryptanalytic attack against FEAL-8 that needed 225 known plaintexts, and other enhancements followed. In the wake of these several attacks, FEAL and its derivatives must be considered insecure.