Paper 2008/004

Efficient Tweakable Enciphering Schemes from (Block-Wise) Universal Hash Functions

Palash Sarkar

Abstract

This paper describes several constructions of tweakable strong pseudorandom permutations (SPRPs) built from different modes of operations of a block cipher and suitable universal hash functions. For the electronic codebook (ECB) based construction, an invertible blockwise universal hash function is required. We simplify an earlier construction of such a function described by Naor and Reingold. The other modes of operations considered are the counter mode and the output feedback (OFB) mode. All the constructions make the same number of block cipher calls and the same number of multiplications. Combined with a class of polynomials defined by Bernstein, the new constructions provide the currently best known algorithms for the important practical problem of disk encryption.

Note: This is a substantially revised version. The length has been considerably reduced while retaining the essential parts of the paper.