Module CAST

CAST-128 symmetric cipher

CAST-128 (or CAST5) is a symmetric block cipher specified in RFC2144.

It has a fixed data block size of 8 bytes. Its key can vary in length from 40 to 128 bits.

CAST is deemed to be cryptographically secure, but its usage is not widespread. Keys of sufficient length should be used to prevent brute force attacks (128 bits are recommended).

As an example, encryption can be done as follows:

>>> from Crypto.Cipher import CAST
>>> from Crypto import Random
>>>
>>> key = b'Sixteen byte key'
>>> iv = Random.new().read(CAST.block_size)
>>> cipher = CAST.new(key, CAST.MODE_OPENPGP, iv)
>>> plaintext = b'sona si latine loqueris '
>>> msg = cipher.encrypt(plaintext)
>>>
...
>>> eiv = msg[:CAST.block_size+2]
>>> ciphertext = msg[CAST.block_size+2:]
>>> cipher = CAST.new(key, CAST.MODE_OPENPGP, eiv)
>>> print cipher.decrypt(ciphertext)