Optimal Tweakable Blockcipher Based on Dual MISTY-Type Structure

In this paper, on the basis of four round Dual MISTY-Type transformations, we give a method to solve an open problem about tweakable blockcipher proposed by Liskov et al. The problem is how to construct tweakable blockciphers without using a pre-existing blockcipher. We show that tweakable blockcipher can be created directly from dual MISTY-Type structure. Concretely, we built and analyze an optimal four round tweakable dual MISTY-Type transformation which use the XOR-universal permutation to replace some round pseudo random permutation and reduce the number of the pseudorandom permutation by using some permutation repeatedly.