// isPubKey returns whether or not the passed public key script is a standard
// pay-to-pubkey script that pays to a valid compressed or uncompressed public
// key along with the serialized pubkey it is paying to if it is.
//
// NOTE: This function ensures the public key is actually valid since the
// compression algorithm requires valid pubkeys.  It does not support hybrid
// pubkeys.  This means that even if the script has the correct form for a
// pay-to-pubkey script, this function will only return true when it is paying
// to a valid compressed or uncompressed pubkey.
func isPubKey(script []byte) (bool, []byte) {
	// Pay-to-compressed-pubkey script.
	if len(script) == 35 && script[0] == txscript.OP_DATA_33 &&
		script[34] == txscript.OP_CHECKSIG && (script[1] == 0x02 ||
		script[1] == 0x03) {

		// Ensure the public key is valid.
		serializedPubKey := script[1:34]
		_, err := btcec.ParsePubKey(serializedPubKey, btcec.S256())
		if err == nil {
			return true, serializedPubKey
		}
	}

	// Pay-to-uncompressed-pubkey script.
	if len(script) == 67 && script[0] == txscript.OP_DATA_65 &&
		script[66] == txscript.OP_CHECKSIG && script[1] == 0x04 {

		// Ensure the public key is valid.
		serializedPubKey := script[1:66]
		_, err := btcec.ParsePubKey(serializedPubKey, btcec.S256())
		if err == nil {
			return true, serializedPubKey
		}
	}

	return false, nil
}

// GetIdentity returns the public identity corresponding to the given address
// if it exists.
func (c *Client) GetIdentity(address string) (*identity.Public, error) {
	addr, err := bmutil.DecodeAddress(address)
	if err != nil {
		return nil, fmt.Errorf("Address decode failed: %v", addr)
	}

	res, err := c.bmd.GetIdentity(context.Background(), &pb.GetIdentityRequest{
		Address: address,
	})
	if grpc.Code(err) == codes.NotFound {
		return nil, ErrIdentityNotFound
	} else if err != nil {
		return nil, err
	}

	signKey, err := btcec.ParsePubKey(res.SigningKey, btcec.S256())
	if err != nil {
		return nil, err
	}
	encKey, err := btcec.ParsePubKey(res.EncryptionKey, btcec.S256())
	if err != nil {
		return nil, err
	}

	return identity.NewPublic(signKey, encKey,
		&pow.Data{
			res.NonceTrials,
			res.ExtraBytes,
		}, addr.Version, addr.Stream), nil
}

func TestPublicKeyIsEqual(t *testing.T) {
	pubKey1, err := btcec.ParsePubKey(
		[]byte{0x03, 0x26, 0x89, 0xc7, 0xc2, 0xda, 0xb1, 0x33,
			0x09, 0xfb, 0x14, 0x3e, 0x0e, 0x8f, 0xe3, 0x96, 0x34,
			0x25, 0x21, 0x88, 0x7e, 0x97, 0x66, 0x90, 0xb6, 0xb4,
			0x7f, 0x5b, 0x2a, 0x4b, 0x7d, 0x44, 0x8e,
		},
		btcec.S256(),
	)
	if err != nil {
		t.Fatalf("failed to parse raw bytes for pubKey1: %v", err)
	}

	pubKey2, err := btcec.ParsePubKey(
		[]byte{0x02, 0xce, 0x0b, 0x14, 0xfb, 0x84, 0x2b, 0x1b,
			0xa5, 0x49, 0xfd, 0xd6, 0x75, 0xc9, 0x80, 0x75, 0xf1,
			0x2e, 0x9c, 0x51, 0x0f, 0x8e, 0xf5, 0x2b, 0xd0, 0x21,
			0xa9, 0xa1, 0xf4, 0x80, 0x9d, 0x3b, 0x4d,
		},
		btcec.S256(),
	)
	if err != nil {
		t.Fatalf("failed to parse raw bytes for pubKey2: %v", err)
	}

	if !pubKey1.IsEqual(pubKey1) {
		t.Fatalf("value of IsEqual is incorrect, %v is "+
			"equal to %v", pubKey1, pubKey1)
	}

	if pubKey1.IsEqual(pubKey2) {
		t.Fatalf("value of IsEqual is incorrect, %v is not "+
			"equal to %v", pubKey1, pubKey2)
	}
}

// TestSigCacheAddEvictEntry tests the eviction case where a new signature
// triplet is added to a full signature cache which should trigger randomized
// eviction, followed by adding the new element to the cache.
func TestSigCacheAddEvictEntry(t *testing.T) {
	// Create a sigcache that can hold up to 100 entries.
	sigCacheSize := uint(100)
	sigCache := NewSigCache(sigCacheSize)

	// Fill the sigcache up with some random sig triplets.
	for i := uint(0); i < sigCacheSize; i++ {
		msg, sig, key, err := genRandomSig()
		if err != nil {
			t.Fatalf("unable to generate random signature test data")
		}

		sigCache.Add(*msg, sig, key)

		sigCopy, _ := btcec.ParseSignature(sig.Serialize(), btcec.S256())
		keyCopy, _ := btcec.ParsePubKey(key.SerializeCompressed(), btcec.S256())
		if !sigCache.Exists(*msg, sigCopy, keyCopy) {
			t.Errorf("previously added item not found in signature" +
				"cache")
		}
	}

	// The sigcache should now have sigCacheSize entries within it.
	if uint(len(sigCache.validSigs)) != sigCacheSize {
		t.Fatalf("sigcache should now have %v entries, instead it has %v",
			sigCacheSize, len(sigCache.validSigs))
	}

	// Add a new entry, this should cause eviction of a randomly chosen
	// previously entry.
	msgNew, sigNew, keyNew, err := genRandomSig()
	if err != nil {
		t.Fatalf("unable to generate random signature test data")
	}
	sigCache.Add(*msgNew, sigNew, keyNew)

	// The sigcache should still have sigCache entries.
	if uint(len(sigCache.validSigs)) != sigCacheSize {
		t.Fatalf("sigcache should now have %v entries, instead it has %v",
			sigCacheSize, len(sigCache.validSigs))
	}

	// The entry added above should be found within the sigcache.
	sigNewCopy, _ := btcec.ParseSignature(sigNew.Serialize(), btcec.S256())
	keyNewCopy, _ := btcec.ParsePubKey(keyNew.SerializeCompressed(), btcec.S256())
	if !sigCache.Exists(*msgNew, sigNewCopy, keyNewCopy) {
		t.Fatalf("previously added item not found in signature cache")
	}
}

func TestPubKeys(t *testing.T) {
	for _, test := range pubKeyTests {
		pk, err := btcec.ParsePubKey(test.key, btcec.S256())
		if err != nil {
			if test.isValid {
				t.Errorf("%s pubkey failed when shouldn't %v",
					test.name, err)
			}
			continue
		}
		if !test.isValid {
			t.Errorf("%s counted as valid when it should fail",
				test.name)
			continue
		}
		var pkStr []byte
		switch test.format {
		case btcec.TstPubkeyUncompressed:
			pkStr = (*btcec.PublicKey)(pk).SerializeUncompressed()
		case btcec.TstPubkeyCompressed:
			pkStr = (*btcec.PublicKey)(pk).SerializeCompressed()
		case btcec.TstPubkeyHybrid:
			pkStr = (*btcec.PublicKey)(pk).SerializeHybrid()
		}
		if !bytes.Equal(test.key, pkStr) {
			t.Errorf("%s pubkey: serialized keys do not match.",
				test.name)
			spew.Dump(test.key)
			spew.Dump(pkStr)
		}
	}
}

// TestSigCacheAddMaxEntriesZeroOrNegative tests that if a sigCache is created
// with a max size <= 0, then no entries are added to the sigcache at all.
func TestSigCacheAddMaxEntriesZeroOrNegative(t *testing.T) {
	// Create a sigcache that can hold up to 0 entries.
	sigCache := NewSigCache(0)

	// Generate a random sigCache entry triplet.
	msg1, sig1, key1, err := genRandomSig()
	if err != nil {
		t.Errorf("unable to generate random signature test data")
	}

	// Add the triplet to the signature cache.
	sigCache.Add(*msg1, sig1, key1)

	// The generated triplet should not be found.
	sig1Copy, _ := btcec.ParseSignature(sig1.Serialize(), btcec.S256())
	key1Copy, _ := btcec.ParsePubKey(key1.SerializeCompressed(), btcec.S256())
	if sigCache.Exists(*msg1, sig1Copy, key1Copy) {
		t.Errorf("previously added signature found in sigcache, but" +
			"shouldn't have been")
	}

	// There shouldn't be any entries in the sigCache.
	if len(sigCache.validSigs) != 0 {
		t.Errorf("%v items found in sigcache, no items should have"+
			"been added", len(sigCache.validSigs))
	}
}

// Uncompress computes the public key for a given compressed public key.
func (cpk *CompressedPublicKey) Uncompress() (*PublicKey, error) {
	// Should only execute the decompression branch of ParsePublicKey
	pk_s, err := btcec.ParsePubKey(cpk[:], S256)
	if err != nil {
		return nil, err
	}

	return newPublicKeyCoords(pk_s.X, pk_s.Y), nil
}

// TstAddressPubKey makes an AddressPubKey, setting the unexported fields with
// the parameters.
func TstAddressPubKey(serializedPubKey []byte, pubKeyFormat PubKeyFormat,
	netID byte) *AddressPubKey {

	pubKey, _ := btcec.ParsePubKey(serializedPubKey, btcec.S256())
	return &AddressPubKey{
		pubKeyFormat: pubKeyFormat,
		pubKey:       (*btcec.PublicKey)(pubKey),
		pubKeyHashID: netID,
	}
}

// authPKH...
func (c *LNDConn) authPKH(
	myId *btcec.PrivateKey, theirPKH, localEphPubBytes []byte) error {
	if c.Authed {
		return fmt.Errorf("%s already authed", c.RemotePub)
	}
	if len(theirPKH) != 20 {
		return fmt.Errorf("remote PKH must be 20 bytes, got %d",
			len(theirPKH))
	}

	// Send 53 bytes: our pubkey, and the remote's pubkey hash.
	var greetingMsg [53]byte
	copy(greetingMsg[:33], myId.PubKey().SerializeCompressed())
	copy(greetingMsg[:33], theirPKH)
	if _, err := c.Conn.Write(greetingMsg[:]); err != nil {
		return err
	}

	// Wait for their response.
	// TODO(tadge): add timeout here
	//  * NOTE(roasbeef): read timeout should be set on the underlying
	//    net.Conn.
	resp := make([]byte, 53)
	if _, err := c.Conn.Read(resp); err != nil {
		return err
	}

	// Parse their long-term public key, and generate the DH proof.
	theirPub, err := btcec.ParsePubKey(resp[:33], btcec.S256())
	if err != nil {
		return err
	}
	idDH := fastsha256.Sum256(btcec.GenerateSharedSecret(myId, theirPub))
	fmt.Printf("made idDH %x\n", idDH)
	theirDHproof := btcutil.Hash160(append(localEphPubBytes, idDH[:]...))

	// Verify that their DH proof matches the one we just generated.
	if bytes.Equal(resp[33:], theirDHproof) == false {
		return fmt.Errorf("Invalid DH proof %x", theirDHproof)
	}

	// If their DH proof checks out, then send our own.
	myDHproof := btcutil.Hash160(append(c.RemotePub.SerializeCompressed(), idDH[:]...))
	if _, err = c.Conn.Write(myDHproof); err != nil {
		return err
	}

	// Proof sent, auth complete.
	c.RemotePub = theirPub
	theirAdr := btcutil.Hash160(theirPub.SerializeCompressed())
	copy(c.RemoteLNId[:], theirAdr[:16])
	c.Authed = true

	return nil
}

// newLnAddr...
func newLnAddr(encodedAddr string) (*lnAddr, error) {
	// The format of an lnaddr is "<pubkey or pkh>@host"
	idHost := strings.Split(encodedAddr, "@")
	if len(idHost) != 2 {
		return nil, fmt.Errorf("invalid format for lnaddr string: %v", encodedAddr)
	}

	// Attempt to resolve the IP address, this handles parsing IPv6 zones,
	// and such.
	fmt.Println("host: ", idHost[1])
	ipAddr, err := net.ResolveTCPAddr("tcp", idHost[1])
	if err != nil {
		return nil, err
	}

	addr := &lnAddr{netAddr: ipAddr}

	idLen := len(idHost[0])
	switch {
	// Is the ID a hex-encoded compressed public key?
	case idLen > 65 && idLen < 69:
		pubkeyBytes, err := hex.DecodeString(idHost[0])
		if err != nil {
			return nil, err
		}

		addr.pubKey, err = btcec.ParsePubKey(pubkeyBytes, btcec.S256())
		if err != nil {
			return nil, err
		}

		// got pubey, populate address from pubkey
		pkh := btcutil.Hash160(addr.pubKey.SerializeCompressed())
		addr.bitcoinAddr, err = btcutil.NewAddressPubKeyHash(pkh,
			&chaincfg.TestNet3Params)
		if err != nil {
			return nil, err
		}
	// Is the ID a string encoded bitcoin address?
	case idLen > 33 && idLen < 37:
		addr.bitcoinAddr, err = btcutil.DecodeAddress(idHost[0],
			&chaincfg.TestNet3Params)
		if err != nil {
			return nil, err
		}
	default:
		return nil, fmt.Errorf("invalid address %s", idHost[0])
	}

	// Finally, populate the lnid from the address.
	copy(addr.lnId[:], addr.bitcoinAddr.ScriptAddress())

	return addr, nil
}

// Verifies a hash using DER encoded signature
func verifyECDSA(pubKey, signature, hash []byte) (bool, error) {
	sig, err := btcec.ParseDERSignature(signature, btcec.S256())
	if err != nil {
		return false, err
	}
	pk, err := btcec.ParsePubKey(pubKey, btcec.S256())
	if err != nil {
		return false, nil
	}
	return sig.Verify(hash, pk), nil
}

// NewKeyFromString returns a new extended key instance from a base58-encoded
// extended key.
func NewKeyFromString(key string) (*ExtendedKey, error) {
	// The base58-decoded extended key must consist of a serialized payload
	// plus an additional 4 bytes for the checksum.
	decoded := base58.Decode(key)
	if len(decoded) != serializedKeyLen+4 {
		return nil, ErrInvalidKeyLen
	}

	// The serialized format is:
	//   version (4) || depth (1) || parent fingerprint (4)) ||
	//   child num (4) || chain code (32) || key data (33) || checksum (4)

	// Split the payload and checksum up and ensure the checksum matches.
	payload := decoded[:len(decoded)-4]
	checkSum := decoded[len(decoded)-4:]
	expectedCheckSum := chainhash.DoubleHashB(payload)[:4]
	if !bytes.Equal(checkSum, expectedCheckSum) {
		return nil, ErrBadChecksum
	}

	// Deserialize each of the payload fields.
	version := payload[:4]
	depth := uint16(payload[4:5][0])
	parentFP := payload[5:9]
	childNum := binary.BigEndian.Uint32(payload[9:13])
	chainCode := payload[13:45]
	keyData := payload[45:78]

	// The key data is a private key if it starts with 0x00.  Serialized
	// compressed pubkeys either start with 0x02 or 0x03.
	isPrivate := keyData[0] == 0x00
	if isPrivate {
		// Ensure the private key is valid.  It must be within the range
		// of the order of the secp256k1 curve and not be 0.
		keyData = keyData[1:]
		keyNum := new(big.Int).SetBytes(keyData)
		if keyNum.Cmp(btcec.S256().N) >= 0 || keyNum.Sign() == 0 {
			return nil, ErrUnusableSeed
		}
	} else {
		// Ensure the public key parses correctly and is actually on the
		// secp256k1 curve.
		_, err := btcec.ParsePubKey(keyData, btcec.S256())
		if err != nil {
			return nil, err
		}
	}

	return newExtendedKey(version, keyData, chainCode, parentFP, depth,
		childNum, isPrivate), nil
}

func (pubKey PubKeySecp256k1) VerifyBytes(msg []byte, sig_ Signature) bool {
	pub__, err := secp256k1.ParsePubKey(append([]byte{0x04}, pubKey[:]...), secp256k1.S256())
	if err != nil {
		return false
	}
	sig, ok := sig_.(SignatureSecp256k1)
	if !ok {
		return false
	}
	sig__, err := secp256k1.ParseDERSignature(sig[:], secp256k1.S256())
	if err != nil {
		return false
	}
	return sig__.Verify(Sha256(msg), pub__)
}

// createCipherConn....
func (l *Listener) createCipherConn(lnConn *LNDConn) (*btcec.PrivateKey, error) {
	var err error
	var theirEphPubBytes []byte

	// First, read and deserialize their ephemeral public key.
	theirEphPubBytes, err = readClear(lnConn.Conn)
	if err != nil {
		return nil, err
	}
	if len(theirEphPubBytes) != 33 {
		return nil, fmt.Errorf("Got invalid %d byte eph pubkey %x\n",
			len(theirEphPubBytes), theirEphPubBytes)
	}
	theirEphPub, err := btcec.ParsePubKey(theirEphPubBytes, btcec.S256())
	if err != nil {
		return nil, err
	}

	// Once we've parsed and verified their key, generate, and send own
	// ephemeral key pair for use within this session.
	myEph, err := btcec.NewPrivateKey(btcec.S256())
	if err != nil {
		return nil, err
	}
	if _, err := writeClear(lnConn.Conn, myEph.PubKey().SerializeCompressed()); err != nil {
		return nil, err
	}

	// Now that we have both keys, do non-interactive diffie with ephemeral
	// pubkeys, sha256 for good luck.
	sessionKey := fastsha256.Sum256(
		btcec.GenerateSharedSecret(myEph, theirEphPub),
	)

	lnConn.chachaStream, err = chacha20poly1305.New(sessionKey[:])

	// display private key for debug only
	fmt.Printf("made session key %x\n", sessionKey)

	lnConn.remoteNonceInt = 1 << 63
	lnConn.myNonceInt = 0

	lnConn.RemotePub = theirEphPub
	lnConn.Authed = false

	return myEph, nil
}

// authPubKey...
func (c *LNDConn) authPubKey(
	myId *btcec.PrivateKey, remotePubBytes, localEphPubBytes []byte) error {
	if c.Authed {
		return fmt.Errorf("%s already authed", c.RemotePub)
	}

	// Since we already know their public key, we can immediately generate
	// the DH proof without an additional round-trip.
	theirPub, err := btcec.ParsePubKey(remotePubBytes, btcec.S256())
	if err != nil {
		return err
	}
	theirPKH := btcutil.Hash160(remotePubBytes)
	idDH := fastsha256.Sum256(btcec.GenerateSharedSecret(myId, theirPub))
	myDHproof := btcutil.Hash160(append(c.RemotePub.SerializeCompressed(), idDH[:]...))

	// Send over the 73 byte authentication message: my pubkey, their
	// pubkey hash, DH proof.
	var authMsg [73]byte
	copy(authMsg[:33], myId.PubKey().SerializeCompressed())
	copy(authMsg[33:], theirPKH)
	copy(authMsg[53:], myDHproof)
	if _, err = c.Conn.Write(authMsg[:]); err != nil {
		return nil
	}

	// Await, their response. They should send only the 20-byte DH proof.
	resp := make([]byte, 20)
	_, err = c.Conn.Read(resp)
	if err != nil {
		return err
	}

	// Verify that their proof matches our locally computed version.
	theirDHproof := btcutil.Hash160(append(localEphPubBytes, idDH[:]...))
	if bytes.Equal(resp, theirDHproof) == false {
		return fmt.Errorf("invalid DH proof %x", theirDHproof)
	}

	// Proof checks out, auth complete.
	c.RemotePub = theirPub
	theirAdr := btcutil.Hash160(theirPub.SerializeCompressed())
	copy(c.RemoteLNId[:], theirAdr[:16])
	c.Authed = true

	return nil
}

// This example demonstrates encrypting a message for a public key that is first
// parsed from raw bytes, then decrypting it using the corresponding private key.
func Example_encryptMessage() {
	// Decode the hex-encoded pubkey of the recipient.
	pubKeyBytes, err := hex.DecodeString("04115c42e757b2efb7671c578530ec191a1" +
		"359381e6a71127a9d37c486fd30dae57e76dc58f693bd7e7010358ce6b165e483a29" +
		"21010db67ac11b1b51b651953d2") // uncompressed pubkey
	if err != nil {
		fmt.Println(err)
		return
	}
	pubKey, err := btcec.ParsePubKey(pubKeyBytes, btcec.S256())
	if err != nil {
		fmt.Println(err)
		return
	}

	// Encrypt a message decryptable by the private key corresponding to pubKey
	message := "test message"
	ciphertext, err := btcec.Encrypt(pubKey, []byte(message))
	if err != nil {
		fmt.Println(err)
		return
	}

	// Decode the hex-encoded private key.
	pkBytes, err := hex.DecodeString("a11b0a4e1a132305652ee7a8eb7848f6ad" +
		"5ea381e3ce20a2c086a2e388230811")
	if err != nil {
		fmt.Println(err)
		return
	}
	// note that we already have corresponding pubKey
	privKey, _ := btcec.PrivKeyFromBytes(btcec.S256(), pkBytes)

	// Try decrypting and verify if it's the same message.
	plaintext, err := btcec.Decrypt(privKey, ciphertext)
	if err != nil {
		fmt.Println(err)
		return
	}

	fmt.Println(string(plaintext))

	// Output:
	// test message
}

func TestPrivKeys(t *testing.T) {
	tests := []struct {
		name string
		key  []byte
	}{
		{
			name: "check curve",
			key: []byte{
				0xea, 0xf0, 0x2c, 0xa3, 0x48, 0xc5, 0x24, 0xe6,
				0x39, 0x26, 0x55, 0xba, 0x4d, 0x29, 0x60, 0x3c,
				0xd1, 0xa7, 0x34, 0x7d, 0x9d, 0x65, 0xcf, 0xe9,
				0x3c, 0xe1, 0xeb, 0xff, 0xdc, 0xa2, 0x26, 0x94,
			},
		},
	}

	for _, test := range tests {
		priv, pub := btcec.PrivKeyFromBytes(btcec.S256(), test.key)

		_, err := btcec.ParsePubKey(
			pub.SerializeUncompressed(), btcec.S256())
		if err != nil {
			t.Errorf("%s privkey: %v", test.name, err)
			continue
		}

		hash := []byte{0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9}
		sig, err := priv.Sign(hash)
		if err != nil {
			t.Errorf("%s could not sign: %v", test.name, err)
			continue
		}

		if !sig.Verify(hash, pub) {
			t.Errorf("%s could not verify: %v", test.name, err)
			continue
		}

		serializedKey := priv.Serialize()
		if !bytes.Equal(serializedKey, test.key) {
			t.Errorf("%s unexpected serialized bytes - got: %x, "+
				"want: %x", test.name, serializedKey, test.key)
		}
	}
}

// TestSigCacheAddExists tests the ability to add, and later check the
// existence of a signature triplet in the signature cache.
func TestSigCacheAddExists(t *testing.T) {
	sigCache := NewSigCache(200)

	// Generate a random sigCache entry triplet.
	msg1, sig1, key1, err := genRandomSig()
	if err != nil {
		t.Errorf("unable to generate random signature test data")
	}

	// Add the triplet to the signature cache.
	sigCache.Add(*msg1, sig1, key1)

	// The previously added triplet should now be found within the sigcache.
	sig1Copy, _ := btcec.ParseSignature(sig1.Serialize(), btcec.S256())
	key1Copy, _ := btcec.ParsePubKey(key1.SerializeCompressed(), btcec.S256())
	if !sigCache.Exists(*msg1, sig1Copy, key1Copy) {
		t.Errorf("previously added item not found in signature cache")
	}
}

// This example demonstrates verifying a secp256k1 signature against a public
// key that is first parsed from raw bytes.  The signature is also parsed from
// raw bytes.
func Example_verifySignature() {
	// Decode hex-encoded serialized public key.
	pubKeyBytes, err := hex.DecodeString("02a673638cb9587cb68ea08dbef685c" +
		"6f2d2a751a8b3c6f2a7e9a4999e6e4bfaf5")
	if err != nil {
		fmt.Println(err)
		return
	}
	pubKey, err := btcec.ParsePubKey(pubKeyBytes, btcec.S256())
	if err != nil {
		fmt.Println(err)
		return
	}

	// Decode hex-encoded serialized signature.
	sigBytes, err := hex.DecodeString("30450220090ebfb3690a0ff115bb1b38b" +
		"8b323a667b7653454f1bccb06d4bbdca42c2079022100ec95778b51e707" +
		"1cb1205f8bde9af6592fc978b0452dafe599481c46d6b2e479")

	if err != nil {
		fmt.Println(err)
		return
	}
	signature, err := btcec.ParseSignature(sigBytes, btcec.S256())
	if err != nil {
		fmt.Println(err)
		return
	}

	// Verify the signature for the message using the public key.
	message := "test message"
	messageHash := wire.DoubleSha256([]byte(message))
	verified := signature.Verify(messageHash, pubKey)
	fmt.Println("Signature Verified?", verified)

	// Output:
	// Signature Verified? true
}

// NewAddressPubKey returns a new AddressPubKey which represents a pay-to-pubkey
// address.  The serializedPubKey parameter must be a valid pubkey and can be
// uncompressed, compressed, or hybrid.
func NewAddressPubKey(serializedPubKey []byte, net *chaincfg.Params) (*AddressPubKey, error) {
	pubKey, err := btcec.ParsePubKey(serializedPubKey, btcec.S256())
	if err != nil {
		return nil, err
	}

	// Set the format of the pubkey.  This probably should be returned
	// from btcec, but do it here to avoid API churn.  We already know the
	// pubkey is valid since it parsed above, so it's safe to simply examine
	// the leading byte to get the format.
	pkFormat := PKFUncompressed
	switch serializedPubKey[0] {
	case 0x02, 0x03:
		pkFormat = PKFCompressed
	case 0x06, 0x07:
		pkFormat = PKFHybrid
	}

	return &AddressPubKey{
		pubKeyFormat: pkFormat,
		pubKey:       pubKey,
		pubKeyHashID: net.PubKeyHashAddrID,
	}, nil
}