Date: 17 May 2006

New block encryption algorithm MISTY


We propose secret-key cryptosystems MISTY1 and MISTY2, which are block ciphers with a 128-bit key, a 64-bit block and a variable number of rounds. MISTY is a generic name for MISTY1 and MISTY2. They are designed on the basis of the theory of provable security against differential and linear cryptanalysis, and moreover they realize high speed encryption on hardware platforms as well as on software environments. Our software implementation shows that MISTY1 with eight rounds can encrypt a data stream in CBC mode at a speed of 20Mbps and 40Mbps on Pentium/100MHz and PA-7200/120MHz, respectively. For its hardware performance, we have produced a prototype LSI by a process of 0.5Μ CMOS gate-array and confirmed a speed of 450Mbps. In this paper, we describe the detailed specifications and design principles of MISTY1 and MISTY2.