MISTY1

MISTY1 is a secret-key block cipher with a 128-bit key, a 64-bit block and a variable number of rounds, described in RFC 2994 by H. Ohta and M. Matsui of Mitsubishi Electric Corporation in November 2000. The authors say it was designed on the basis of the theory of provable security against differential and linear cryptanalysis while also encrypting quickly on hardware and in software, and that eight rounds are recommended and used in most cases. The algorithm has a key scheduling part, which expands the 128-bit key into a 128-bit expanded key, and a data randomizing part, which mixes the 64-bit input using the functions FO, FL and FI; decryption runs the data randomizing part in reverse order. The authors report that an eight-round software implementation encrypted a data stream in CBC mode at 57 Mbps on a Pentium II at 266 MHz, and that a prototype 0.8-micron CMOS gate-array chip reached 512 Mbps.