Utilization of multiple block cipher hashing in authentication and digital signatures

Abstract

A new algorithm for authentication and digital signature is introduced. It is based on using four different hash functions classified as very secure against all attacks except the brute force one. The hash function used is selected by computing nf/sub i/=r/sub i/ mod 4 where r/sub i/ is randomly generated and the initial hash sequence H/sub 0/ is publicized by the sender. According to nf/sub i/, he/she prepares every message block M/sub i/ for encryption by applying a special block cipher technique to obtain the cipher block C/sub i/. Then, the corresponding new hash value H/sub i/ is obtained. The value r/sub i/ is encrypted to R/sub i/ using the sender's secret RSA key d/sub s/ and then the receiver's public one e/sub r/ (this could be reversed if n/sub r/>n/sub s/ where n/sub r/ and n/sub s/ are the modulus numbers of the receiver and sender respectively). The code sent by the sender to the receiver is composed of the combination (C/sub i/, H/sub i/, R/sub i/). This could be useful in checking the integrity of the transmitted message as a whole. The receiver reads the public values H/sub 0/, e/sub s/ and n/sub s/. Then he/she decrypts the cipher C/sub i/ and uses his private RSA key d/sub r/ and the senders public one e/sub s/ to decrypt R/sub i/. Decryption of C/sub i/ yields the prepared block before encryption and decryption of R/sub i/ yields the value r/sub i/. Using r/sub i/, the receiver can compute nf/sub i/=r/sub i/ mod 4. Using nf/sub i/ and H/sub i-1/, he/she can compute the message block M/sub i/' and the hash value H/sub i/'. If H/sub i/'=H/sub i/ then M/sub i/'=M/sub i/ and this means that the message block M/sub i/' was sent by the sender. If this condition is not satisfied, then the message is either changed or sent by another sender. This algorithm is easy to implement and hard to attack.