Java Code Examples for org.bouncycastle.math.ec.ECPoint#Fp

/**
 * <p>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.</p>
 * <p>
 * <p>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.</p>
 * <p>
 * <p>If this method returns null it means recovery was not possible and recId should be iterated.</p>
 * <p>
 * <p>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.</p>
 *
 * @param recId       Which possible key to recover.
 * @param sig         the R and S components of the signature, wrapped.
 * @param messageHash Hash of the data that was signed.
 * @return 65-byte encoded public key
 */
public static byte[] recoverPubBytesFromSignature(int recId, ECDSASignature sig, byte[] messageHash) {
    check(recId >= 0, "recId must be positive");
    check(sig.r.signum() >= 0, "r must be positive");
    check(sig.s.signum() >= 0, "s must be positive");
    check(messageHash != null, "messageHash must not 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 = 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.
    ECCurve.Fp curve = (ECCurve.Fp) CURVE.getCurve();
    BigInteger prime = curve.getQ();  // Bouncy Castle is not consistent about the letter it uses for the prime.
    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, messageHash);
    //   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.Fp q = (ECPoint.Fp) ECAlgorithms.sumOfTwoMultiplies(CURVE.getG(), eInvrInv, R, srInv);
    return q.getEncoded(/* compressed */ false);
}
 

/**
 * Calculates the sent address of an EthereumTransaction. Note this can be a costly operation to calculate. . This requires that you have Bouncy castle as a dependency in your project
 *
 *
 * @param eTrans transaction
 * @param chainId chain identifier (e.g. 1 main net)
 * @return sent address as byte array
 */
public static byte[] getSendAddress(EthereumTransaction eTrans, int chainId) {
	// init, maybe we move this out to save time
	X9ECParameters params = SECNamedCurves.getByName("secp256k1");
	ECDomainParameters CURVE=new ECDomainParameters(params.getCurve(), params.getG(), params.getN(), params.getH());	 // needed for getSentAddress

 
    byte[] transactionHash;

    if ((eTrans.getSig_v()[0]==chainId*2+EthereumUtil.CHAIN_ID_INC) || (eTrans.getSig_v()[0]==chainId*2+EthereumUtil.CHAIN_ID_INC+1)) {  // transaction hash with dummy signature data
    	 transactionHash = EthereumUtil.getTransactionHashWithDummySignatureEIP155(eTrans);
    } else {  // transaction hash without signature data
	 transactionHash = EthereumUtil.getTransactionHashWithoutSignature(eTrans);
    }
  // signature to address
	BigInteger bR = new BigInteger(1,eTrans.getSig_r());
	BigInteger bS = new BigInteger(1,eTrans.getSig_s());
  // calculate v for signature
	byte v =(byte) (eTrans.getSig_v()[0]);
	if (!((v == EthereumUtil.LOWER_REAL_V) || (v== (LOWER_REAL_V+1)))) {
		byte vReal = EthereumUtil.LOWER_REAL_V;
		if (((int)v%2 == 0)) {
			v = (byte) (vReal+0x01);
		} else {
			v = vReal;
		}
	}


	// the following lines are inspired from ECKey.java of EthereumJ, but adapted to the hadoopcryptoledger context
	if (v < 27 || v > 34) {
		LOG.error("Header out of Range:  "+v);
		throw new RuntimeException("Header out of range "+v);
	}
	if (v>=31) {

		v -=4;
	}
	int receiverId = v - 27;
	BigInteger n = CURVE.getN();
    BigInteger i = BigInteger.valueOf((long) receiverId / 2);
    BigInteger x = bR.add(i.multiply(n));
    ECCurve.Fp curve = (ECCurve.Fp) CURVE.getCurve();
    BigInteger prime = curve.getQ();
    if (x.compareTo(prime) >= 0) {
        return null;
     }
    // decompress Key
    X9IntegerConverter x9 = new X9IntegerConverter();
    byte[] compEnc = x9.integerToBytes(x, 1 + x9.getByteLength(CURVE.getCurve()));
    boolean yBit=(receiverId & 1) == 1;
    compEnc[0] = (byte)(yBit ? 0x03 : 0x02);
    ECPoint R =  CURVE.getCurve().decodePoint(compEnc);
    if (!R.multiply(n).isInfinity()) {
    		return null;
    }
    BigInteger e = new BigInteger(1,transactionHash);
    BigInteger eInv = BigInteger.ZERO.subtract(e).mod(n);
    BigInteger rInv = bR.modInverse(n);
    BigInteger srInv = rInv.multiply(bS).mod(n);
    BigInteger eInvrInv = rInv.multiply(eInv).mod(n);
    ECPoint.Fp q = (ECPoint.Fp) ECAlgorithms.sumOfTwoMultiplies(CURVE.getG(), eInvrInv, R, srInv);
    byte[] pubKey=q.getEncoded(false);
    // now we need to convert the public key into an ethereum send address which is the last 20 bytes of 32 byte KECCAK-256 Hash of the key.
	Keccak.Digest256 digest256 = new Keccak.Digest256();
	digest256.update(pubKey,1,pubKey.length-1);
	byte[] kcck = digest256.digest();
    return Arrays.copyOfRange(kcck,12,kcck.length);
}