Simple, unoptimised implementation of Montgomery multiplication and modular exponentiation intended for RSA encryption and Diffie Hellman key exchange schemes. Montgomery multiplication is an efficient modular multiplication algorithm. Based on: http://www.hackersdelight.org/hdcodetxt/mont64.c.txt crypto.c - Modular arithmetic functions run.c - A test program consts.hs - Haskell program to precompute constants needed for Montgomery multiplication