How to use the ecdsa.util function in ecdsa

elif _is_ecdsa(rrsig.algorithm):
            if rrsig.algorithm == ECDSAP256SHA256:
                curve = ecdsa.curves.NIST256p
                key_len = 32
                digest_len = 32
            elif rrsig.algorithm == ECDSAP384SHA384:
                curve = ecdsa.curves.NIST384p
                key_len = 48
                digest_len = 48
            else:
                # shouldn't happen
                raise ValidationFailure('unknown ECDSA curve')
            keyptr = candidate_key.key
            x = ecdsa.util.string_to_number(keyptr[0:key_len])
            y = ecdsa.util.string_to_number(keyptr[key_len:key_len * 2])
            assert ecdsa.ecdsa.point_is_valid(curve.generator, x, y)
            point = ecdsa.ellipticcurve.Point(curve.curve, x, y, curve.order)
            verifying_key = ecdsa.keys.VerifyingKey.from_public_point(point, curve)
            r = rrsig.signature[:key_len]
            s = rrsig.signature[key_len:]
            sig = ecdsa.ecdsa.Signature(ecdsa.util.string_to_number(r),
                                        ecdsa.util.string_to_number(s))

        else:
            raise ValidationFailure('unknown algorithm %u' % rrsig.algorithm)

        hash.update(_to_rdata(rrsig, origin)[:18])
        hash.update(rrsig.signer.to_digestable(origin))

        if rrsig.labels < len(rrname) - 1:
            suffix = rrname.split(rrsig.labels + 1)[1]

def get_transaction_signature(transaction, private_key):
    """
    Gets the sigscript of a raw transaction
    private_key should be in bytes form
    """
    packed_raw_transaction = get_packed_transaction(transaction)
    hash = hashlib.sha256(hashlib.sha256(packed_raw_transaction).digest()).digest()
    public_key = address_utils.get_public_key(private_key)
    key = SigningKey.from_string(private_key, curve=SECP256k1)
    signature = key.sign_digest(hash, sigencode=util.sigencode_der_canonize)
    signature += bytes.fromhex("01") #hash code type

    sigscript = struct.pack("

def verify_message(address, signature, message):
    """ See http://www.secg.org/download/aid-780/sec1-v2.pdf for the math """
    from ecdsa import numbertheory, ellipticcurve, util
    curve = curve_secp256k1
    G = generator_secp256k1
    order = G.order()
    # extract r,s from signature
    sig = base64.b64decode(signature)
    if len(sig) != 65: raise BaseException("Wrong encoding")
    r,s = util.sigdecode_string(sig[1:], order)
    nV = ord(sig[0])
    if nV < 27 or nV >= 35:
        return False
    if nV >= 31:
        compressed = True
        nV -= 4
    else:
        compressed = False
    recid = nV - 27
    # 1.1
    x = r + (recid/2) * order
    # 1.3
    alpha = ( x * x * x  + curve.a() * x + curve.b() ) % curve.p()
    beta = modular_sqrt(alpha, curve.p())
    y = beta if (beta - recid) % 2 == 0 else curve.p() - beta
    # 1.4 the constructor checks that nR is at infinity

hash.update(rrnamebuf)
            hash.update(rrfixed)
            rrdata = rr.to_digestable(origin)
            rrlen = struct.pack('!H', len(rrdata))
            hash.update(rrlen)
            hash.update(rrdata)

        digest = hash.digest()

        if _is_rsa(rrsig.algorithm):
            digest = _make_algorithm_id(rrsig.algorithm) + digest
            if pubkey.verify(bytearray(sig), bytearray(digest)):
                return

        elif _is_ecdsa(rrsig.algorithm):
            diglong = ecdsa.util.string_to_number(digest)
            if verifying_key.pubkey.verifies(diglong, sig):
                return

        else:
            raise ValidationFailure('unknown algorithm %s' % rrsig.algorithm)

    raise ValidationFailure('verify failure')

public_key_algo = der.first_child(subject_pki)
        ii = der.first_child(public_key_algo)
        self.public_key_algo = decode_OID(der.get_value_of_type(ii, 'OBJECT IDENTIFIER'))

        if self.public_key_algo != '1.2.840.10045.2.1':  # for non EC public key
            # pubkey modulus and exponent
            subject_public_key = der.next_node(public_key_algo)
            spk = der.get_value_of_type(subject_public_key, 'BIT STRING')
            spk = ASN1_Node(bitstr_to_bytestr(spk))
            r = spk.root()
            modulus = spk.first_child(r)
            exponent = spk.next_node(modulus)
            rsa_n = spk.get_value_of_type(modulus, 'INTEGER')
            rsa_e = spk.get_value_of_type(exponent, 'INTEGER')
            self.modulus = ecdsa.util.string_to_number(rsa_n)
            self.exponent = ecdsa.util.string_to_number(rsa_e)
        else:
            subject_public_key = der.next_node(public_key_algo)
            spk = der.get_value_of_type(subject_public_key, 'BIT STRING')
            self.ec_public_key = spk

        # extensions
        self.CA = False
        self.AKI = None
        self.SKI = None
        i = subject_pki
        while i[2] < cert[2]:
            i = der.next_node(i)
            d = der.get_dict(i)
            for oid, value in d.items():
                value = ASN1_Node(value)
                if oid == '2.5.29.19':

def compressedPubkey(pk):
    if SECP256K1_MODULE == "cryptography" and not isinstance(
        pk, ecdsa.keys.VerifyingKey
    ):
        order = ecdsa.SECP256k1.order
        x = pk.public_numbers().x
        y = pk.public_numbers().y
    else:  # pragma: no cover
        order = pk.curve.generator.order()
        p = pk.pubkey.point
        x = p.x()
        y = p.y()
    x_str = ecdsa.util.number_to_string(x, order)
    return _bytes(chr(2 + (y & 1))) + x_str

def verify(self, msg, key, sig):
        try:
            return key.verify(sig, msg, hashfunc=self.hash_alg,
                              sigdecode=ecdsa.util.sigdecode_string)
        except AssertionError:
            return False

def _create_entropy(self) :
        ''' '''
        ba = bytearray(os.urandom(32))
        seed = sha256(ba)
        return ecdsa.util.PRNG(seed)

def checkd_data_sig(self,sig,pre,pk):
        sec, compressed = self.keypair.get(pk)
        pre_hash = Hash(pre)
        pkey = regenerate_key(sec)
        secexp = pkey.secret
        private_key = MySigningKey.from_secret_exponent(secexp, curve=ecdsa.SECP256k1)
        public_key = private_key.get_verifying_key()
        print("Data signature ok:")
        print(public_key.verify_digest(sig[:-1], pre_hash, sigdecode=ecdsa.util.sigdecode_der))

def compressedPubkey(pk):
    if SECP256K1_MODULE == "cryptography" and not isinstance(pk, ecdsa.keys.VerifyingKey):
        order = ecdsa.SECP256k1.order
        x = pk.public_numbers().x
        y = pk.public_numbers().y
    else:
        order = pk.curve.generator.order()
        p = pk.pubkey.point
        x = p.x()
        y = p.y()
    x_str = ecdsa.util.number_to_string(x, order)
    return py23_bytes(chr(2 + (y & 1)), 'ascii') + x_str