io.neow3j.crypto.Sign Maven / Gradle / Ivy
package io.neow3j.crypto;
import static io.neow3j.utils.Assertions.verifyPrecondition;
import io.neow3j.constants.NeoConstants;
import io.neow3j.contract.Hash160;
import io.neow3j.crypto.ECKeyPair.ECPrivateKey;
import io.neow3j.crypto.ECKeyPair.ECPublicKey;
import io.neow3j.utils.ArrayUtils;
import io.neow3j.utils.Numeric;
import java.math.BigInteger;
import java.security.SignatureException;
import java.util.Arrays;
import org.bouncycastle.asn1.x9.X9IntegerConverter;
import org.bouncycastle.math.ec.ECAlgorithms;
import org.bouncycastle.math.ec.ECPoint;
import org.bouncycastle.math.ec.FixedPointCombMultiplier;
import org.bouncycastle.math.ec.custom.sec.SecP256R1Curve;
/**
* Transaction signing logic.
*
* Originally adapted from the
*
* BitcoinJ ECKey implementation.
*
*
Class from web3j project, and adapted to neow3j project (with NEO requirements).
*/
public class Sign {
private static final int LOWER_REAL_V = 27;
public static SignatureData signMessage(byte[] message, ECKeyPair keyPair) {
return signMessage(message, keyPair, true);
}
public static SignatureData signMessage(byte[] message, ECKeyPair keyPair, boolean needToHash) {
byte[] messageHash;
if (needToHash) {
messageHash = Hash.sha256(message);
} else {
messageHash = message;
}
ECDSASignature sig = keyPair.signAndGetECDSASignature(messageHash);
// Now we have to work backwards to figure out the recId needed to recover the signature.
int recId = -1;
for (int i = 0; i < 4; i++) {
ECPublicKey k = recoverFromSignature(i, sig, messageHash);
if (k != null && k.equals(keyPair.getPublicKey())) {
recId = i;
break;
}
}
if (recId == -1) {
throw new RuntimeException(
"Could not construct a recoverable key. This should never happen.");
}
int headerByte = recId + 27;
// 1 header + 32 bytes for R + 32 bytes for S
byte v = (byte) headerByte;
byte[] r = Numeric.toBytesPadded(sig.r, 32);
byte[] s = Numeric.toBytesPadded(sig.s, 32);
return new SignatureData(v, r, s);
}
/**
* Given the components of a signature and a selector value, recover and return the public
* key that generated the signature according to the algorithm in SEC1v2 section 4.1.6.
*
* The recId is an index from 0 to 3 which indicates which of the 4 possible keys is the
* correct one. Because the key recovery operation yields multiple potential keys, the correct
* key must either be stored alongside the signature, or you must be willing to try each recId
* in turn until you find one that outputs the key you are expecting.
*
* If this method returns null it means recovery was not possible and recId should be
* iterated.
*
* Given the above two points, a correct usage of this method is inside a for loop from
* 0 to 3, and if the output is null OR a key that is not the one you expect, you try again with
* the next recId.
*
* @param recId Which possible key to recover.
* @param sig the R and S components of the signature, wrapped.
* @param message Hash of the data that was signed.
* @return An ECKey containing only the public part, or null if recovery wasn't possible.
*/
public static ECPublicKey recoverFromSignature(int recId, ECDSASignature sig, byte[] message) {
verifyPrecondition(recId >= 0, "recId must be positive");
verifyPrecondition(sig.r.signum() >= 0, "r must be positive");
verifyPrecondition(sig.s.signum() >= 0, "s must be positive");
verifyPrecondition(message != null, "message cannot be null");
// 1.0 For j from 0 to h (h == recId here and the loop is outside this function)
// 1.1 Let x = r + jn
BigInteger n = NeoConstants.curve().getN(); // Curve order.
BigInteger i = BigInteger.valueOf((long) recId / 2);
BigInteger x = sig.r.add(i.multiply(n));
// 1.2. Convert the integer x to an octet string X of length mlen using the conversion
// routine specified in Section 2.3.7, where mlen = ⌈(log2 p)/8⌉ or mlen = ⌈m/8⌉.
// 1.3. Convert the octet string (16 set binary digits)||X to an elliptic curve point R
// using the conversion routine specified in Section 2.3.4. If this conversion
// routine outputs "invalid", then do another iteration of Step 1.
//
// More concisely, what these points mean is to use X as a compressed public key.
BigInteger prime = SecP256R1Curve.q;
if (x.compareTo(prime) >= 0) {
// Cannot have point co-ordinates larger than this as everything takes place modulo Q.
return null;
}
// Compressed keys require you to know an extra bit of data about the y-coord as there are
// two possibilities. So it's encoded in the recId.
ECPoint R = decompressKey(x, (recId & 1) == 1);
// 1.4. If nR != point at infinity, then do another iteration of Step 1 (callers
// responsibility).
if (!R.multiply(n).isInfinity()) {
return null;
}
// 1.5. Compute e from M using Steps 2 and 3 of ECDSA signature verification.
BigInteger e = new BigInteger(1, message);
// 1.6. For k from 1 to 2 do the following. (loop is outside this function via
// iterating recId)
// 1.6.1. Compute a candidate public key as:
// Q = mi(r) * (sR - eG)
//
// Where mi(x) is the modular multiplicative inverse. We transform this into the following:
// Q = (mi(r) * s ** R) + (mi(r) * -e ** G)
// Where -e is the modular additive inverse of e, that is z such that z + e = 0 (mod n).
// In the above equation ** is point multiplication and + is point addition (the EC group
// operator).
//
// We can find the additive inverse by subtracting e from zero then taking the mod. For
// example the additive inverse of 3 modulo 11 is 8 because 3 + 8 mod 11 = 0, and
// -3 mod 11 = 8.
BigInteger eInv = BigInteger.ZERO.subtract(e).mod(n);
BigInteger rInv = sig.r.modInverse(n);
BigInteger srInv = rInv.multiply(sig.s).mod(n);
BigInteger eInvrInv = rInv.multiply(eInv).mod(n);
ECPoint q = ECAlgorithms.sumOfTwoMultiplies(NeoConstants.curve().getG(), eInvrInv, R, srInv);
return new ECPublicKey(q);
}
/**
* Decompress a compressed public key (x co-ord and low-bit of y-coord).
*
* Based on: https://tools.ietf.org/html/rfc5480#section-2.2
*/
private static ECPoint decompressKey(BigInteger xBN, boolean yBit) {
X9IntegerConverter x9 = new X9IntegerConverter();
byte[] compEnc = x9.integerToBytes(xBN,
1 + x9.getByteLength(NeoConstants.curve().getCurve()));
compEnc[0] = (byte) (yBit ? 0x03 : 0x02);
return NeoConstants.curve().getCurve().decodePoint(compEnc);
}
/**
* Given an arbitrary piece of text and an NEO message signature encoded in bytes, returns the
* public key that was used to sign it. This can then be compared to the expected public key to
* determine if the signature was correct.
*
* @param message encoded message.
* @param signatureData The message signature components
* @return the public key used to sign the message
* @throws SignatureException If the public key could not be recovered or if there was a
* signature format error.
*/
public static ECPublicKey signedMessageToKey(
byte[] message, SignatureData signatureData) throws SignatureException {
byte[] r = signatureData.getR();
byte[] s = signatureData.getS();
verifyPrecondition(r != null && r.length == 32, "r must be 32 bytes");
verifyPrecondition(s != null && s.length == 32, "s must be 32 bytes");
// unsigned byte to int
int header = signatureData.getV() & 0xFF;
// The header byte: 0x1B = first key with even y, 0x1C = first key with odd y,
// 0x1D = second key with even y, 0x1E = second key with odd y
if (header < 27 || header > 34) {
throw new SignatureException("Header byte out of range: " + header);
}
ECDSASignature sig = new ECDSASignature(
new BigInteger(1, signatureData.getR()),
new BigInteger(1, signatureData.getS()));
byte[] messageHash = Hash.sha256(message);
int recId = header - 27;
ECPublicKey key = recoverFromSignature(recId, sig, messageHash);
if (key == null) {
throw new SignatureException("Could not recover public key from signature");
}
return key;
}
/**
* Returns public key from the given private key.
*
* @param privKey the private key to derive the public key from
* @return BigInteger encoded public key
*/
public static ECPublicKey publicKeyFromPrivate(ECPrivateKey privKey) {
return new ECPublicKey(publicPointFromPrivateKey(privKey));
}
/**
* Returns public key point from the given private key.
*
* @param privKey The private key as BigInteger
* @return The ECPoint object representation of the public key based on the given private key
*/
public static ECPoint publicPointFromPrivateKey(ECPrivateKey privKey) {
BigInteger key = privKey.getInt();
/*
* TODO: FixedPointCombMultiplier currently doesn't support scalars longer than the group
* order, but that could change in future versions.
*/
if (key.bitLength() > NeoConstants.curve().getN().bitLength()) {
key = key.mod(NeoConstants.curve().getN());
}
return new FixedPointCombMultiplier().multiply(NeoConstants.curve().getG(), key)
.normalize();
}
/**
* Recovers the address that created the given signature on the given message.
*
* If the message is a Neo transaction, then make sure that it was serialized without the
* verification and invocation script attached (i.e. without the signature).
*
* @param signatureData The signature.
* @param message The message for which the signature was created.
* @return the address that produced the signature data from the transaction.
* @throws SignatureException throws if the signature is invalid.
*/
public static String recoverSigningAddress(byte[] message, SignatureData signatureData)
throws SignatureException {
byte v = signatureData.getV();
byte[] r = signatureData.getR();
byte[] s = signatureData.getS();
SignatureData signatureDataV = new Sign.SignatureData(getRealV(v), r, s);
ECPublicKey key = Sign.signedMessageToKey(message, signatureDataV);
return Hash160.fromPublicKey(key.getEncoded(true)).toAddress();
}
private static byte getRealV(byte v) {
if (v == LOWER_REAL_V || v == (LOWER_REAL_V + 1)) {
return v;
}
byte realV = LOWER_REAL_V;
int inc = 0;
if ((int) v % 2 == 0) {
inc = 1;
}
return (byte) (realV + inc);
}
public static class SignatureData {
private final byte v;
private final byte[] r;
private final byte[] s;
public SignatureData(byte v, byte[] r, byte[] s) {
this.v = v;
this.r = r;
this.s = s;
}
public static SignatureData fromByteArray(byte[] signature) {
return new SignatureData(
(byte) 0x00,
Arrays.copyOfRange(signature, 0, 32),
Arrays.copyOfRange(signature, 32, 64)
);
}
public byte getV() {
return v;
}
public byte[] getR() {
return r;
}
public byte[] getS() {
return s;
}
public byte[] getConcatenated() {
return ArrayUtils.concatenate(r, s);
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
SignatureData that = (SignatureData) o;
if (v != that.v) {
return false;
}
if (!Arrays.equals(r, that.r)) {
return false;
}
return Arrays.equals(s, that.s);
}
@Override
public int hashCode() {
int result = (int) v;
result = 31 * result + Arrays.hashCode(r);
result = 31 * result + Arrays.hashCode(s);
return result;
}
@Override
public String toString() {
return "SignatureData{" +
"v=" + v +
", r=" + Arrays.toString(r) +
", s=" + Arrays.toString(s) +
'}';
}
}
}