OPTIMIZATION OFADVANCEDENCRYPTION STANDARD (AES)IN FPGA IMPLEMENTATIONUSING S-BOX INTEGRATION

Cryptography has a significant role in the security of data transmission. The algorithm of Rijndael was selected and adopted by National Institute of Standards and Technology (NIST) U.S. as Advanced Encryption Standard (AES) in October 2000, in order to replace the old Data Encryption Standard (DES). As compared to software, hardware implementations provide more physical security as well as faster speed. Thus, in this project, the AES cryptograph was simulated with FPGA, by using Verilog HDL. The main objectives are the architectural and algorithmic optimizations of the AES implementation, which would in turn benefit applications that are both speed and area critical. The optimization methodology in this project was achieved using S-Box integration. S-Box, which is for SubBytes, and Inverse S-Box, which is for InvSubBytes, are both constituted of two 256-byte substitution tables. In fact, it is usual that in any high speed full pipelining AES implementations, it would require 24 S-Box tables and 16 InverseS-Box tables at any one time. Nonetheless, mathematical formulas show that S-Box and Inverse S-Box could actually beachieved with only g,fand/1. Multiplicative inverse, org, is a 256-byte look-up table. On the other hand, affine transformation,/, and its inverse,/7, can be implemented with a limited number of XOR gates. Accordingly, the number of substitution tables necessitated could be reduced by half. Consequently, the new implementation would still obtain the identical S-Box and Inverse S-Box values, but merely from one look-up table and some simple logic gates. The new design shows that it can deliver a throughput of 203 Mbit/sec with hardware of 78,977 gate counts. Hardware complexity is reduced to 69% of its originalwhile still able to function at core process of only 12 cycles.