Fast Implementation of SMS4 Cryptographic Algorithms on Smart Card

SMS4 is the first national standard of cryptographic algorithm in China. It is a block cipher with 128 bits key. Because SMS4 is a relatively new algorithm, there are no hardware accelerators specific to it and no proposal to implement it on smart cards until now. In this paper, SMS4 was designed and implemented on smart cards. At first, the optimized implementation algorithm of SMS4 was given so as to improve the speed and reserve the memory. We used byte swap to accelerate circular shift operations in a 32-bit vector and parallel key expansion to reserve the memory for round keys on 8-bit smart cards. The optimized algorithm was implemented in 8051 assembly language and run on SLE66CLX800PE hardware emulator. The test results show that the performance gain of our optimization is obvious and fast implementation of SMS4 is proven applicable on smart cards with average encryption/decryption time about 0.68 ms at system clock 30 MHz.