Efficient permutation instructions for fast software cryptography

Abstract

To achieve pervasive secure information processing over the public wired and wireless Internet, it is desirable to be able to perform cryptographic transformations rapidly and conveniently. The performance of software-implemented cryptographic functions is hampered by certain operations which have not been optimized in the Instruction Set Architecture of processors, due to their infrequency in earlier programming workloads. One such operation is the permutation of bits within a block to be encrypted, which is particularly difficult in word-oriented processors. This paper introduces four novel permutation instructions and the underlying methodology for performing arbitrary n-bit permutations efficiently in programmable processors. While targeted at solving the more difficult problem of permuting n 1-bit elements, we also address the issue of permuting a smaller number of multi-bit subwords packed into an n-bit word, a feature needed to accelerate multimedia processing in software. By providing the ability to do fast permutations in software, we open the field for new cryptography and multimedia algorithms using these powerful yet simple permutation primitives. This results in much faster cryptography and multimedia processing, while retaining the flexibility of software implementations, for secure multimedia information appliances and servers