Low efficiency is a main problem when the RISC microprocessors implement S-box substitution operation.In order to attack it

an approach is proposed in this paper

which is done by extending instructions through designing special module and instruction for S-box substitution

thus raising the performance of it.A new kind of Sbox substitution module and operation instruction is designed based on the characteristics of S-box substitution operation of block cipher algorithm

which can support the four common modes of S-box substitution module

i.e.

8-32

8-8

6-4

4-4mode.The circuit implementing S-box substitution module is then designed adopting the Boolean function method.The concept is finally verified in EDA software

which shows the validity of the method and reveals the significant improved performance.