def mac(self, s, x, secret):
        if secret:
            secret_hash = h(secret)
            return hn(s + x + secret_hash + s, self.ss_hash_iterations)
        else:
            return h(s + x + s)
obfs2 regular MAC: MAC(s, x) = H(s | x | s)
dataset/ETHPy150Open isislovecruft/obfsproxy/obfsproxy/transports/obfs2.py/Obfs2Transport.mac