Speeding Up the Wide-Pipe: Secure and Fast Hashing

In this paper we propose a new sequential mode of operation – the Fast wide pipe or FWP for short – to hash messages of arbitrary length. The mode is shown to be (1) preimage-resistance preserving, (2) collision-resistance-preserving and, most importantly, (3) indifferentiable from a random oracle up to O(2) compression function invocations. In addition, our rigorous investigation suggests that any variants of Joux’s multi-collision, Kelsey-Schneier 2nd preimage and Herding attack are also ineffective on this mode. This fact leads us to conjecture that the indifferentiability security bound of FWP can be extended beyond the birthday barrier. From the point of view of efficiency, this new mode, for example, is always faster than the Wide-pipe mode when both modes use an identical compression function. In particular, it is nearly twice as fast as the Wide-pipe for a reasonable selection of the input and output size of the compression function. We also compare the FWP with several other modes of operation.