// String returns the extended key as a human-readable base58-encoded string.
func (k *ExtendedKey) String() (string, error) {
if len(k.key) == 0 {
return "", fmt.Errorf("zeroed extended key")
}
var childNumBytes [4]byte
depthByte := byte(k.depth % 256)
binary.BigEndian.PutUint32(childNumBytes[:], k.childNum)
// The serialized format is:
// version (4) || depth (1) || parent fingerprint (4)) ||
// child num (4) || chain code (32) || key data (33) || checksum (4)
serializedBytes := make([]byte, 0, serializedKeyLen+4)
serializedBytes = append(serializedBytes, k.version...)
serializedBytes = append(serializedBytes, depthByte)
serializedBytes = append(serializedBytes, k.parentFP...)
serializedBytes = append(serializedBytes, childNumBytes[:]...)
serializedBytes = append(serializedBytes, k.chainCode...)
if k.isPrivate {
serializedBytes = append(serializedBytes, 0x00)
serializedBytes = append(serializedBytes, k.key...)
} else {
serializedBytes = append(serializedBytes, k.pubKeyBytes()...)
}
checkSum := chainhash.HashFuncB(chainhash.HashFuncB(serializedBytes))[:4]
serializedBytes = append(serializedBytes, checkSum...)
return base58.Encode(serializedBytes), 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.HashFuncB(chainhash.HashFuncB(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
}
// String creates the Wallet Import Format string encoding of a WIF structure.
// See DecodeWIF for a detailed breakdown of the format and requirements of
// a valid WIF string.
func (w *WIF) String() string {
// Precalculate size. Maximum number of bytes before base58 encoding
// is two bytes for the network, one byte for the ECDSA type, 32 bytes
// of private key and finally four bytes of checksum.
encodeLen := 2 + 1 + 32 + 4
a := make([]byte, 0, encodeLen)
a = append(a, w.netID[:]...)
a = append(a, byte(w.ecType))
a = append(a, w.PrivKey.Serialize()...)
cksum := chainhash.HashFuncB(a)
a = append(a, cksum[:4]...)
return base58.Encode(a)
}
// DecodeWIF creates a new WIF structure by decoding the string encoding of
// the import format.
//
// The WIF string must be a base58-encoded string of the following byte
// sequence:
//
// * 2 bytes to identify the network, must be 0x80 for mainnet or 0xef for
// either testnet or the regression test network
// * 1 extra byte
// * 32 bytes of a binary-encoded, big-endian, zero-padded private key
// * 4 bytes of checksum, must equal the first four bytes of the double SHA256
// of every byte before the checksum in this sequence
//
// If the base58-decoded byte sequence does not match this, DecodeWIF will
// return a non-nil error. ErrMalformedPrivateKey is returned when the WIF
// is of an impossible length. ErrChecksumMismatch is returned if the
// expected WIF checksum does not match the calculated checksum.
func DecodeWIF(wif string) (*WIF, error) {
decoded := base58.Decode(wif)
decodedLen := len(decoded)
if decodedLen != 39 {
return nil, ErrMalformedPrivateKey
}
// Checksum is first four bytes of hash of the identifier byte
// and privKey. Verify this matches the final 4 bytes of the decoded
// private key.
cksum := chainhash.HashFuncB(decoded[:decodedLen-4])
if !bytes.Equal(cksum[:4], decoded[decodedLen-4:]) {
return nil, address.ErrChecksumMismatch
}
netID := [2]byte{decoded[0], decoded[1]}
privKeyBytes := decoded[3 : 3+btcec.PrivKeyBytesLen]
privKey, _ := btcec.PrivKeyFromBytes(curve, privKeyBytes)
return &WIF{0, *privKey, netID}, nil
}
// checksum: first four bytes of hash^2
func checksum(input []byte) (cksum [4]byte) {
h := chainhash.HashFuncB(input)
h2 := chainhash.HashFuncB(h[:])
copy(cksum[:], h2[:4])
return
}
// Hash160 calculates the hash ripemd160(hash256(b)).
func Hash160(buf []byte) []byte {
return calcHash(chainhash.HashFuncB(buf), ripemd160.New())
}