Compact Implementation of Threefish and Skein on FPGA

The SHA-3 finalist Skein is built from the tweakable Threefish block cipher. In order to have a better understanding of the computational efficiency of Skein (resource sharing, memory access scheme, scheduling, etc.), the authors design a low-area coprocessor for Threefish and describe how to implement Skein on their architecture. They harness the intrinsic parallelism of Threefish to design a pipelined ALU and interleave several tasks in order to achieve a tight scheduling. From their point of view, the main advantage of Skein over other SHA-3 finalists is that the same coprocessor allows one to encrypt or hash a message.