hmac.py

'''
something something docstring
'''
from Crypto.Hash import SHA


BLOCK_SIZE = SHA.digest_size
O_CONST = 0x5c
I_CONST = 0x36


def hmac_sha1(key, msg):
    '''
    Returns an HMAC of the key and msg
    '''
    if len(key) > BLOCK_SIZE:
        key = SHA.new(data=key).hexdigest()
    key = key + bytearray(BLOCK_SIZE - len(key))
    o_key_pad = bytearray([key[i] ^ O_CONST for i in range(BLOCK_SIZE)])
    i_key_pad = bytearray([key[i] ^ I_CONST for i in range(BLOCK_SIZE)])
    second_half = SHA.new(i_key_pad + msg).hexdigest()
    return SHA.new(o_key_pad + second_half).hexdigest()


def working_hmac(key, msg):
    import hmac
    from hashlib import sha1
    return hmac.HMAC(key, msg, sha1).hexdigest()


def pycrypto_hmac(key, msg):
    from Crypto.Hash import HMAC
    return HMAC.new(key, msg=msg, digestmod=SHA).hexdigest()


if __name__ == '__main__':
    print hmac_sha1('poop', 'here is a stinky message')
    print
    print working_hmac('poop', 'here is a stinky message')
    print
    print pycrypto_hmac('poop', 'here is a stinky message')