Verify that our own 'sig_val' carries the signature of 'm' by the
        key associated to the Cert 'cert'.

def _verify_sig(self, m, cert):
        """
        Verify that our own 'sig_val' carries the signature of 'm' by the
        key associated to the Cert 'cert'.
        """
        if self.sig_val:
            if self.sig_alg:
                h, sig = _tls_hash_sig[self.sig_alg].split('+')
                if sig.endswith('pss'):
                    t = "pss"
                else:
                    t = "pkcs"
                return cert.verify(m, self.sig_val, t=t, h=h)
            else:
                if self.tls_session.tls_version >= 0x0300:
                    return cert.verify(m, self.sig_val, t='pkcs', h='md5-sha1')
                else:
                    return cert.verify(m, self.sig_val, t='pkcs', h='md5')
        return False