This is an RSA Cryptosystem implemented in C for educational purposes, in May 2012. It has a command line user interface and supports the encryption and decryption of numbers and text. The public and private keys generated are 1024 bits long. The source code contains implementations of the Miller-Rabin primality test, the "Square and Multiply" algorithm for modular exponentiation and the Extended Euclidian Algorithm.
To compile this library you will need to install the GMP library (for large number support) available at http://gmplib.org/