Simple AES/DES encryption and SHA1/SHA2 hashing library

Crypto provides a simple implementation of the Rijndael (now AES) and DES
encryption algorithms as well as the SHA1 and SHA2 hashing algorithms. The
library is almost a verbatim copy of the code from OpenBSD and PuTTY.

This version is the one used by the SoftDevLabs version of
Hercules 4.x (Hyperion).