.. module:: hmac
   
****
HMAC
****

This module implements the HMAC algorithm as described by `RFC 2104 <https://tools.ietf.org/html/rfc2104.html>`_.

The module is based on the C library `cifra <https://github.com/ctz/cifra>`_.

    
.. class:: HMAC(key,hashfn)
    
    Return a new hmac object. *key* is a bytes or bytearray or string object giving the secret key. *hashfn* is an
    instance of a hash function to use in hmac generation. It supports any class in the :samp:`crypto.hash` module.
    
.. method:: update(data)

    Update the hmac object with the string *data*. Repeated calls are equivalent to a single call with the concatenation of all
    the arguments: m.update(a); m.update(b) is equivalent to m.update(a+b).
        
.. method:: digest()

    Return the digest of the strings passed to the update method so far. The size depends on *hashfn*.
        
.. method:: hexdigest()

    Like digest except the digest is returned as a string containing only hexadecimal digits.