RFC 2994 (rfc2994) - Page 1 of 10

A Description of the MISTY1 Encryption Algorithm

Network Working Group                                            H. Ohta
Request for Comments: 2994                                     M. Matsui
Category: Informational                  Mitsubishi Electric Corporation
                                                           November 2000


            A Description of the MISTY1 Encryption Algorithm

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   This document describes a secret-key cryptosystem MISTY1, which is
   block cipher with a 128-bit key, a 64-bit block and a variable number
   of rounds.  It documents the algorithm description including key
   scheduling part and data randomizing part.

1. Introduction

   This document describes a secret-key cryptosystem MISTY1, which is
   block cipher with a 128-bit key, a 64-bit block and a variable number
   of rounds.  It is designed on the basis of the theory of provable
   security against differential and linear cryptanalysis, and moreover
   it realizes high-speed encryption on hardware platforms as well as on
   software environments.  As the result of weighing strength and speed,
   8-rounds of MISTY1 is recommended and used in most cases.

   Our implementation shows that MISTY1 with eight rounds can encrypt a
   data stream in CBC mode at a speed of 57Mbps and 40Mbps on Pentium
   II/266MHz and PA-7200/120MHz, respectively.  For its hardware
   performance, we have produced a prototype LSI by a process of 0.8-
   micron CMOS gate-array and confirmed a speed of 512Mbps.

2. Algorithm Description

   Algorithm [1] could be divided into two parts, namely "key scheduling
   part" and "data randomizing part".  Key scheduling part takes a 128-
   bit input key and produces a 128-bit expanded key.  Data randomizing





Ohta & Matsui                Informational