// 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))
	}
}

func TestEncodeDecodeWIF(t *testing.T) {
	priv1, _ := btcec.PrivKeyFromBytes(btcec.S256(), []byte{
		0x0c, 0x28, 0xfc, 0xa3, 0x86, 0xc7, 0xa2, 0x27,
		0x60, 0x0b, 0x2f, 0xe5, 0x0b, 0x7c, 0xae, 0x11,
		0xec, 0x86, 0xd3, 0xbf, 0x1f, 0xbe, 0x47, 0x1b,
		0xe8, 0x98, 0x27, 0xe1, 0x9d, 0x72, 0xaa, 0x1d})

	priv2, _ := btcec.PrivKeyFromBytes(btcec.S256(), []byte{
		0xdd, 0xa3, 0x5a, 0x14, 0x88, 0xfb, 0x97, 0xb6,
		0xeb, 0x3f, 0xe6, 0xe9, 0xef, 0x2a, 0x25, 0x81,
		0x4e, 0x39, 0x6f, 0xb5, 0xdc, 0x29, 0x5f, 0xe9,
		0x94, 0xb9, 0x67, 0x89, 0xb2, 0x1a, 0x03, 0x98})

	wif1, err := NewWIF(priv1, &chaincfg.MainNetParams, false)
	if err != nil {
		t.Fatal(err)
	}
	wif2, err := NewWIF(priv2, &chaincfg.TestNet3Params, true)
	if err != nil {
		t.Fatal(err)
	}

	tests := []struct {
		wif     *WIF
		encoded string
	}{
		{
			wif1,
			"5HueCGU8rMjxEXxiPuD5BDku4MkFqeZyd4dZ1jvhTVqvbTLvyTJ",
		},
		{
			wif2,
			"cV1Y7ARUr9Yx7BR55nTdnR7ZXNJphZtCCMBTEZBJe1hXt2kB684q",
		},
	}

	for _, test := range tests {
		// Test that encoding the WIF structure matches the expected string.
		s := test.wif.String()
		if s != test.encoded {
			t.Errorf("TestEncodeDecodePrivateKey failed: want '%s', got '%s'",
				test.encoded, s)
			continue
		}

		// Test that decoding the expected string results in the original WIF
		// structure.
		w, err := DecodeWIF(test.encoded)
		if err != nil {
			t.Error(err)
			continue
		}
		if got := w.String(); got != test.encoded {
			t.Errorf("NewWIF failed: want '%v', got '%v'", test.wif, got)
		}
	}
}

// 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 := wire.DoubleSha256(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
}

// 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
	// previous 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 TestScalarMult(t *testing.T) {
	// Strategy for this test:
	// Get a random exponent from the generator point at first
	// This creates a new point which is used in the next iteration
	// Use another random exponent on the new point.
	// We use BaseMult to verify by multiplying the previous exponent
	// and the new random exponent together (mod N)
	s256 := btcec.S256()
	x, y := s256.Gx, s256.Gy
	exponent := big.NewInt(1)
	for i := 0; i < 1024; i++ {
		data := make([]byte, 32)
		_, err := rand.Read(data)
		if err != nil {
			t.Fatalf("failed to read random data at %d", i)
			break
		}
		x, y = s256.ScalarMult(x, y, data)
		exponent.Mul(exponent, new(big.Int).SetBytes(data))
		xWant, yWant := s256.ScalarBaseMult(exponent.Bytes())
		if x.Cmp(xWant) != 0 || y.Cmp(yWant) != 0 {
			t.Fatalf("%d: bad output for %X: got (%X, %X), want (%X, %X)", i, data, x, y, xWant, yWant)
			break
		}
	}
}

// NewMaster creates a new master node for use in creating a hierarchical
// deterministic key chain.  The seed must be between 128 and 512 bits and
// should be generated by a cryptographically secure random generation source.
//
// NOTE: There is an extremely small chance (< 1 in 2^127) the provided seed
// will derive to an unusable secret key.  The ErrUnusable error will be
// returned if this should occur, so the caller must check for it and generate a
// new seed accordingly.
func NewMaster(seed []byte, net *chaincfg.Params) (*ExtendedKey, error) {
	// Per [BIP32], the seed must be in range [MinSeedBytes, MaxSeedBytes].
	if len(seed) < MinSeedBytes || len(seed) > MaxSeedBytes {
		return nil, ErrInvalidSeedLen
	}

	// First take the HMAC-SHA512 of the master key and the seed data:
	//   I = HMAC-SHA512(Key = "Bitcoin seed", Data = S)
	hmac512 := hmac.New(sha512.New, masterKey)
	hmac512.Write(seed)
	lr := hmac512.Sum(nil)

	// Split "I" into two 32-byte sequences Il and Ir where:
	//   Il = master secret key
	//   Ir = master chain code
	secretKey := lr[:len(lr)/2]
	chainCode := lr[len(lr)/2:]

	// Ensure the key in usable.
	secretKeyNum := new(big.Int).SetBytes(secretKey)
	if secretKeyNum.Cmp(btcec.S256().N) >= 0 || secretKeyNum.Sign() == 0 {
		return nil, ErrUnusableSeed
	}

	parentFP := []byte{0x00, 0x00, 0x00, 0x00}
	return newExtendedKey(net.HDPrivateKeyID[:], secretKey, chainCode,
		parentFP, 0, 0, true), nil
}

// PrivKey returns the private key for the address.  It can fail if the address
// manager is watching-only or locked, or the address does not have any keys.
//
// This is part of the ManagedPubKeyAddress interface implementation.
func (a *managedAddress) PrivKey() (*btcec.PrivateKey, error) {
	// No private keys are available for a watching-only address manager.
	if a.manager.watchingOnly {
		return nil, managerError(ErrWatchingOnly, errWatchingOnly, nil)
	}

	a.manager.mtx.Lock()
	defer a.manager.mtx.Unlock()

	// Account manager must be unlocked to decrypt the private key.
	if a.manager.locked {
		return nil, managerError(ErrLocked, errLocked, nil)
	}

	// Decrypt the key as needed.  Also, make sure it's a copy since the
	// private key stored in memory can be cleared at any time.  Otherwise
	// the returned private key could be invalidated from under the caller.
	privKeyCopy, err := a.unlock(a.manager.cryptoKeyPriv)
	if err != nil {
		return nil, err
	}

	privKey, _ := btcec.PrivKeyFromBytes(btcec.S256(), privKeyCopy)
	zero.Bytes(privKeyCopy)
	return privKey, nil
}

// This example demonstrates signing a message with a secp256k1 private key that
// is first parsed form raw bytes and serializing the generated signature.
func Example_signMessage() {
	// Decode a hex-encoded private key.
	pkBytes, err := hex.DecodeString("22a47fa09a223f2aa079edf85a7c2d4f87" +
		"20ee63e502ee2869afab7de234b80c")
	if err != nil {
		fmt.Println(err)
		return
	}
	privKey, pubKey := btcec.PrivKeyFromBytes(btcec.S256(), pkBytes)

	// Sign a message using the private key.
	message := "test message"
	messageHash := wire.DoubleSha256([]byte(message))
	signature, err := privKey.Sign(messageHash)
	if err != nil {
		fmt.Println(err)
		return
	}

	// Serialize and display the signature.
	fmt.Printf("Serialized Signature: %x\n", signature.Serialize())

	// Verify the signature for the message using the public key.
	verified := signature.Verify(messageHash, pubKey)
	fmt.Printf("Signature Verified? %v\n", verified)

	// Output:
	// Serialized Signature: 304402201008e236fa8cd0f25df4482dddbb622e8a8b26ef0ba731719458de3ccd93805b022032f8ebe514ba5f672466eba334639282616bb3c2f0ab09998037513d1f9e3d6d
	// Signature Verified? true
}

// This example demonstrates decrypting a message using a private key that is
// first parsed from raw bytes.
func Example_decryptMessage() {
	// Decode the hex-encoded private key.
	pkBytes, err := hex.DecodeString("a11b0a4e1a132305652ee7a8eb7848f6ad" +
		"5ea381e3ce20a2c086a2e388230811")
	if err != nil {
		fmt.Println(err)
		return
	}

	privKey, _ := btcec.PrivKeyFromBytes(btcec.S256(), pkBytes)

	ciphertext, err := hex.DecodeString("35f644fbfb208bc71e57684c3c8b437402ca" +
		"002047a2f1b38aa1a8f1d5121778378414f708fe13ebf7b4a7bb74407288c1958969" +
		"00207cf4ac6057406e40f79961c973309a892732ae7a74ee96cd89823913b8b8d650" +
		"a44166dc61ea1c419d47077b748a9c06b8d57af72deb2819d98a9d503efc59fc8307" +
		"d14174f8b83354fac3ff56075162")

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

	fmt.Println(string(plaintext))

	// Output:
	// test message
}

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)
		}
	}
}

// pubKeyBytes returns bytes for the serialized compressed public key associated
// with this extended key in an efficient manner including memoization as
// necessary.
//
// When the extended key is already a public key, the key is simply returned as
// is since it's already in the correct form.  However, when the extended key is
// a private key, the public key will be calculated and memoized so future
// accesses can simply return the cached result.
func (k *ExtendedKey) pubKeyBytes() []byte {
	// Just return the key if it's already an extended public key.
	if !k.isPrivate {
		return k.key
	}

	// This is a private extended key, so calculate and memoize the public
	// key if needed.
	if len(k.pubKey) == 0 {
		pkx, pky := btcec.S256().ScalarBaseMult(k.key)
		pubKey := btcec.PublicKey{Curve: btcec.S256(), X: pkx, Y: pky}
		k.pubKey = pubKey.SerializeCompressed()
	}

	return k.pubKey
}

// ECPrivKey converts the extended key to a btcec private key and returns it.
// As you might imagine this is only possible if the extended key is a private
// extended key (as determined by the IsPrivate function).  The ErrNotPrivExtKey
// error will be returned if this function is called on a public extended key.
func (k *ExtendedKey) ECPrivKey() (*btcec.PrivateKey, error) {
	if !k.isPrivate {
		return nil, ErrNotPrivExtKey
	}

	privKey, _ := btcec.PrivKeyFromBytes(btcec.S256(), k.key)
	return privKey, nil
}

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)
		}
	}
}

// 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
}

// 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")
	}
}

// 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,
	}
}

func TestGenerateSharedSecret(t *testing.T) {
	privKey1, err := btcec.NewPrivateKey(btcec.S256())
	if err != nil {
		t.Errorf("private key generation error: %s", err)
		return
	}
	privKey2, err := btcec.NewPrivateKey(btcec.S256())
	if err != nil {
		t.Errorf("private key generation error: %s", err)
		return
	}

	secret1 := btcec.GenerateSharedSecret(privKey1, privKey2.PubKey())
	secret2 := btcec.GenerateSharedSecret(privKey2, privKey1.PubKey())

	if !bytes.Equal(secret1, secret2) {
		t.Errorf("ECDH failed, secrets mismatch - first: %x, second: %x",
			secret1, secret2)
	}
}

func main() {
	fi, err := os.Create("secp256k1.go")
	if err != nil {
		log.Fatal(err)
	}
	defer fi.Close()

	// Compress the serialized byte points.
	serialized := btcec.S256().SerializedBytePoints()
	var compressed bytes.Buffer
	w := zlib.NewWriter(&compressed)
	if _, err := w.Write(serialized); err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	w.Close()

	// Encode the compressed byte points with base64.
	encoded := make([]byte, base64.StdEncoding.EncodedLen(compressed.Len()))
	base64.StdEncoding.Encode(encoded, compressed.Bytes())

	fmt.Fprintln(fi, "// Copyright (c) 2015 The btcsuite developers")
	fmt.Fprintln(fi, "// Use of this source code is governed by an ISC")
	fmt.Fprintln(fi, "// license that can be found in the LICENSE file.")
	fmt.Fprintln(fi)
	fmt.Fprintln(fi, "package btcec")
	fmt.Fprintln(fi)
	fmt.Fprintln(fi, "// Auto-generated file (see genprecomps.go)")
	fmt.Fprintln(fi, "// DO NOT EDIT")
	fmt.Fprintln(fi)
	fmt.Fprintf(fi, "var secp256k1BytePoints = %q\n", string(encoded))

	a1, b1, a2, b2 := btcec.S256().EndomorphismVectors()
	fmt.Println("The following values are the computed linearly " +
		"independent vectors needed to make use of the secp256k1 " +
		"endomorphism:")
	fmt.Printf("a1: %x\n", a1)
	fmt.Printf("b1: %x\n", b1)
	fmt.Printf("a2: %x\n", a2)
	fmt.Printf("b2: %x\n", b2)
}

func TestSignCompact(t *testing.T) {
	for i := 0; i < 256; i++ {
		name := fmt.Sprintf("test %d", i)
		data := make([]byte, 32)
		_, err := rand.Read(data)
		if err != nil {
			t.Errorf("failed to read random data for %s", name)
			continue
		}
		compressed := i%2 != 0
		testSignCompact(t, name, btcec.S256(), data, compressed)
	}
}

// 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
}