def _calcResponse(challenge, nonce, password):
return sha1('<STR_LIT>' % (challenge, nonce, password)).digest()<EOL>
Compute the response to the given challenge.

@type challenge: C{str}
@param challenge: An arbitrary byte string, probably received in response
    to (or generated for) the L{PasswordLogin} command.

@type nonce: C{str}
@param nonce: An arbitrary byte string, generated by the client to include
    in the hash to avoid making the client an oracle.

@type password: C{str}
@param password: The known correct password for the account being
    authenticated.

@rtype: C{str}
@return: A hash constructed from the three parameters.