FEAL

FEAL, the Fast data Encipherment Algorithm, is a block cipher proposed as an alternative to the Data Encryption Standard and designed to run much faster in software. Akihiro Shimizu and Shoji Miyaguchi of NTT first published this Feistel based design in 1987. Several revisions followed, all Feistel ciphers using the same basic round function on a 64-bit block. FEAL-4 has four rounds and a 64-bit key, FEAL-8 doubled the rounds, and FEAL-N and FEAL-NX let the user choose the round count, with FEAL-NX using a 128-bit key. Each version fell to cryptanalysis, including attacks by Bert den Boer, Sean Murphy, Eli Biham and Adi Shamir, and Mitsuru Matsui and Atsuhiro Yamagishi. FEAL is remembered less for its use than as a catalyst in the discovery of differential and linear cryptanalysis.