This module implements a chaining block cipher using a one
     way hash.  This method of encryption is the same that is
     used by radius (RFC2138) and is also described in Applied
     Cryptography.

     Two interfaces are provided in the module.  The first is
     straight block encryption/decryption the second does base64
     mime encoding/decoding of the encrypted/decrypted blocks.

     The idea is the the two sides have a shared secret that
     supplies one of the keys and a randomly generated block of
     bytes provides the second key.  The random key is passed in
     cleartext between the two sides.

     An example client and server are packaged as modules with
     this module.  They are used in the tests.