This module currently supports Cipher Block Chaining (CBC) mode. See http://www.itl.nist.gov/fipspubs/fip81.htm for further details.
In CBC or Cipher Block Chaining mode each block is XORed with the previous enciphered block before encryption. For the first block, start with an initialization vector. Take an encryption function, an initialisation vector, a key and a list of blocks and return the encrypted blocks using CBC.
To decipher in CBC or Cipher Block Chaining mode, decipher each block, then XOR the result with the previous block of plaintext result. Note that the initialization vector is treated as the zeroth block of plaintext. Take a decryption function, an initialisation vector, a key and a list of encrypted blocks using CBC and return plaintext blocks.