Research and design of subword shift unit based on inverse butterfly network

The iterative property of inverse butterfly permutation network makes it possible to implement shift operation with simple routing algorithm, which has high application value in cryptography, digital image processing and other fields. Based on the inverse butterfly network, this paper proposes a subword shift unit, which integrates the operations of subword rotation shift, subword logical shift and subword arithmetic shift, extends the function of the shift unit. In this paper, the generation process of routing-bits and mask-selecting-bits is unified into the same algorithm and hardware structure, which reduces the hardware area effectively. The algorithm also implements the unification of bidirectional shift, and solves the problem that the scheme of calculating the complement can not generate the mask-selecting-bits in two directions. The unit increases the area and latency by only 5.1% and 3.3% in the case that the implemented shift operation types are extended by 37.5%, thus achieving an efficient extension of the shift function.