/** @throws HDDerivationException if privKeyBytes is invalid (0 or >= n). */
public static DeterministicKey createMasterPrivKeyFromBytes(byte[] privKeyBytes, byte[] chainCode)
throws HDDerivationException {
BigInteger priv = new BigInteger(1, privKeyBytes);
assertNonZero(priv, "Generated master key is invalid.");
assertLessThanN(priv, "Generated master key is invalid.");
return new DeterministicKey(ImmutableList.<ChildNumber>of(), chainCode, priv, null);
}
private static RawKeyBytes deriveChildKeyBytesFromPrivate(
DeterministicKey parent, ChildNumber childNumber) throws HDDerivationException {
checkArgument(parent.hasPrivKey(), "Parent key must have private key bytes for this method.");
byte[] parentPublicKey = ECKey.compressPoint(parent.getPubKeyPoint()).getEncoded();
assert parentPublicKey.length == 33 : parentPublicKey.length;
ByteBuffer data = ByteBuffer.allocate(37);
if (childNumber.isHardened()) {
data.put(parent.getPrivKeyBytes33());
} else {
data.put(parentPublicKey);
}
data.putInt(childNumber.i());
byte[] i = HDUtils.hmacSha512(parent.getChainCode(), data.array());
assert i.length == 64 : i.length;
byte[] il = Arrays.copyOfRange(i, 0, 32);
byte[] chainCode = Arrays.copyOfRange(i, 32, 64);
BigInteger ilInt = new BigInteger(1, il);
assertLessThanN(ilInt, "Illegal derived key: I_L >= n");
final BigInteger priv = parent.getPrivKey();
BigInteger ki = priv.add(ilInt).mod(ECKey.CURVE.getN());
assertNonZero(ki, "Illegal derived key: derived private key equals 0.");
return new RawKeyBytes(ki.toByteArray(), chainCode);
}
private static RawKeyBytes deriveChildKeyBytes(DeterministicKey parent, ChildNumber childNumber)
throws HDDerivationException {
byte[] parentPublicKey = HDUtils.getBytes(parent.getPubPoint());
assert parentPublicKey.length == 33 : parentPublicKey.length;
ByteBuffer data = ByteBuffer.allocate(37);
if (childNumber.isPrivateDerivation()) {
data.put(parent.getPrivKeyBytes33());
} else {
data.put(parentPublicKey);
}
data.putInt(childNumber.getI());
byte[] i = HDUtils.hmacSha512(parent.getChainCode(), data.array());
assert i.length == 64 : i.length;
byte[] il = Arrays.copyOfRange(i, 0, 32);
byte[] chainCode = Arrays.copyOfRange(i, 32, 64);
BigInteger ilInt = HDUtils.toBigInteger(il);
assertLessThanN(ilInt, "Illegal derived key: I_L >= n");
byte[] keyBytes;
final BigInteger privAsFieldElement = parent.getPrivAsFieldElement();
if (privAsFieldElement != null) {
BigInteger ki = privAsFieldElement.add(ilInt).mod(HDUtils.getEcParams().getN());
assertNonZero(ki, "Illegal derived key: derived private key equals 0.");
keyBytes = ki.toByteArray();
} else {
checkArgument(
!childNumber.isPrivateDerivation(),
"Can't use private derivation with public keys only.");
ECPoint Ki = HDUtils.getEcParams().getG().multiply(ilInt).add(parent.getPubPoint());
checkArgument(
!Ki.equals(HDUtils.getCurve().getInfinity()),
"Illegal derived key: derived public key equals infinity.");
keyBytes = HDUtils.toCompressed(Ki.getEncoded());
}
return new RawKeyBytes(keyBytes, chainCode);
}