Many new challenges have been emerging in the information security area such as encryption

digital signature

identification

etc..Public key cryptosystem is the only solution.Modular exponentiation of large operands is the kernel operation in many public key cryptosystems.It is also the bottleneck of the computing efficiency.Based on Montgomery algorithm

a novel systolic array for modular multiplication is presented in this article.Moreover

with the binary method

a 256 bit systolic modular exponentiation processor

THM256 has been successfully designed and fabricated with 0.8μm CMOS technology.The die area is 17 63mm 2.with 18677 equivalent gates.It can run at 90MHz or higher frequency under 5V and less than 1 5W of power consumption

which means the throughput of 117kbits/s for modular exponentiation calculation.