Security

Running Head : FEAL

Fast data Encryption Algorithm

May , 2008

Abstract

Cryptography is the most effective way to store and secure communications in the fields of data communications and information processing systems .1 FEAL ' stands for Fast Encryption algorithm Because of the high cost and difficult implementation of DES cryptographic algorithm , FEAL is gaining popularity . Because of low cost and ease of its implementation with software and hardware , it can be used in personal computer communications .2 On the other hand it is equally safe and reliable like DES encryption

algorithm . FEAL was invented and promoted by NTT in 1987 . It was designed to replace the DES . A drawback of FEAL is that it provides less security than DES Since its invention , many improved versions have been introduced 3 . The FEAL 2 .0 version is virtually safe from all key attacks because 64-bit key is used to control it which is safer than the 56-bit key (that is used in DES encryption algorithm . As far as cipher text randomization is concerned , FEAL is considered safer because the indices for randomization are much closer than the theoretical values . It was

Two indices are introduced in FEAL design which is M and Ms they are called evaluation indices and are used to evaluate objectively ability of algorithm to randomize data . The indices M and Ms indicates the approximate degree of cipher text variation to the binomial distribution b (n , 1 /2 , where n is the bit length of cipher text

M indicates the approximate degree of cipher text distribution according to plain text and variation from 1-bit to n-bit . The other index Ms denotes the approximate degree of standard deviation

BODY

General block diagram

FEAL consists of two processing parts . First part deals with the 64 bits input and the 2nd part is used to handle the 64 bit key . Both run parallel . In the initialization step 64 bit input and 64 bit key are operated by permutation process . As a result 64-bit input is divided into two halves , which are LEFT HALF 32bit and RIGHT HALF 32bit . On the other hand permutated key in breakdown into two halves of 28-bit each Both halves transform undergo the permutation twice after binary transformation . 64-bit key and RIGHT HALF 32-bit undergo cipher function and combines with LEFT HALF 32-bit . The 64-bit key , after the second permutation now known as sub-key 2 (48-bits , join the 64-bit input in second round of cipher function . This process continues up to desired number of rounds . After the last round the data in finally permutated again which gives the 64-bits output

KEY BLOCK DIAGRAM

the data randomizer is constructed from f as follows

Figure-1

the key schedule is constructed from f_ (k )as follows The two functions are very similar and appear as follows Encryption Process

The encryption process in FEAL has two processing parts . First part is designed to generate the 256-bit extended key from the 64-bit secret key .4 it is designed to generate different extended keys for...