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peacekeeperpeacekeeper
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refactor: Small update to Schnorr signatures
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+218
-2
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3 files changed

+218
-2
lines changed

‎src/main/java/com/danubetech/keyformats/crypto/impl/secp256k1_ES256KS_PrivateKeySigner.java‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
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package com.danubetech.keyformats.crypto.impl;
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import com.danubetech.keyformats.crypto.PrivateKeySigner;
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import com.danubetech.keyformats.crypto.provider.SHA256Provider;
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import com.danubetech.keyformats.jose.JWSAlgorithm;
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import com.miketwk.schnorr.core.Schnorr;
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import org.bitcoinj.crypto.ECKey;
@@ -19,7 +20,7 @@ public byte[] sign(byte[] content) throws GeneralSecurityException {
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// sign
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byte[] hash = Schnorr.sha256(content);
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byte[] hash = SHA256Provider.get().sha256(content);
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byte[] signatureBytes = Schnorr.schnorr_sign(hash, this.getPrivateKey().getPrivKey());
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// done

‎src/main/java/com/danubetech/keyformats/crypto/impl/secp256k1_ES256KS_PublicKeyVerifier.java‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
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package com.danubetech.keyformats.crypto.impl;
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import com.danubetech.keyformats.crypto.PublicKeyVerifier;
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import com.danubetech.keyformats.crypto.provider.SHA256Provider;
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import com.danubetech.keyformats.jose.JWSAlgorithm;
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import com.miketwk.schnorr.core.Schnorr;
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import org.bitcoinj.crypto.ECKey;
@@ -19,7 +20,7 @@ public boolean verify(byte[] content, byte[] signature) throws GeneralSecurityEx
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// verify
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byte[] hash = Schnorr.sha256(content);
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byte[] hash = SHA256Provider.get().sha256(content);
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boolean verified = Schnorr.schnorr_verify(hash, this.getPublicKey().getPubKey(), signature);
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// done

‎src/main/java/com/danubetech/keyformats/util/SchnorrUtil.java‎

Lines changed: 214 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,214 @@
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package com.danubetech.keyformats.util;
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import java.math.BigInteger;
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import java.security.MessageDigest;
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import java.security.NoSuchAlgorithmException;
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/**
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* Schnorr implementation
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*
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* @author michaeltan
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*/
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public class SchnorrUtil {
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public static final BigInteger p=new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F",16);
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public static final BigInteger n=new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141",16);
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public static final BigInteger[] G= {
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new BigInteger("79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798",16),
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new BigInteger("483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8",16)
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};
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public static final BigInteger TWO=BigInteger.valueOf(2);
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public static final BigInteger THREE=BigInteger.valueOf(3);
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private final static char[] hexArray = "0123456789ABCDEF".toCharArray();
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public static BigInteger[] point_add(BigInteger[] p1, BigInteger[] p2) {
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if(p1==null || p1.length!=2)
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return p2;
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if(p2==null || p2.length!=2)
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return p1;
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if(p1[0].compareTo(p2[0])==0 && p1[1].compareTo(p2[1])!=0)
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return null;
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BigInteger lam;
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if(p1[0].compareTo(p2[0])==0 && p1[1].compareTo(p2[1])==0)
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lam=(THREE.multiply(p1[0]).multiply(p1[0]).multiply(TWO.multiply(p1[1]).modPow(p.subtract(TWO), p))).mod(p);
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else
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lam=(p2[1].subtract(p1[1]).multiply(p2[0].subtract(p1[0]).modPow(p.subtract(TWO), p))).mod(p);
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BigInteger x3=(lam.multiply(lam).subtract(p1[0]).subtract(p2[0])).mod(p);
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return new BigInteger[] {x3, lam.multiply(p1[0].subtract(x3)).subtract(p1[1]).mod(p)};
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}
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public static BigInteger[] point_mul(BigInteger[] P, BigInteger n) {
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BigInteger[] R=null;
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for(int i=0; i<256; i++) {
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if(BigInteger.ONE.compareTo(n.shiftRight(i).and(BigInteger.ONE))==0)
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R=point_add(R,P);
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P=point_add(P,P);
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}
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return R;
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}
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public static BigInteger jacobi(BigInteger x) {
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return x.modPow(p.subtract(BigInteger.ONE).divide(TWO), p);
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}
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public static BigInteger[] point_from_bytes(byte[] b) {
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if(b[0]!=2 && b[0]!=3)
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return null;
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BigInteger odd=b[0]==3 ? BigInteger.ONE:BigInteger.ZERO;
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BigInteger x=toBigInteger(b,1,32);
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BigInteger y_sq=x.modPow(THREE, p).add(BigInteger.valueOf(7)).mod(p);
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BigInteger y0=y_sq.modPow(p.add(BigInteger.ONE).divide(BigInteger.valueOf(4)), p);
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if(y_sq.compareTo(y0.modPow(TWO, p))!=0)
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return null;
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BigInteger y=y0.and(BigInteger.ONE).compareTo(odd) !=0 ? p.subtract(y0) : y0;
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return new BigInteger[] {x,y};
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}
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public static byte[] to32BytesData(BigInteger num) {
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String hexNum=num.toString(16);
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if(hexNum.length()<64) {
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StringBuilder sb=new StringBuilder();
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for(int i=0; i<64-hexNum.length(); i++)
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sb.append("0");
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hexNum=sb.append(hexNum).toString();
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}
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return hexStringToByteArray(hexNum);
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}
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public static BigInteger toBigInteger(byte[] data, int startPos, int len) {
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return new BigInteger(bytesToHex(data, startPos, len),16);
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}
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public static BigInteger toBigInteger(byte[] data) {
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return new BigInteger(bytesToHex(data),16);
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}
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public static byte[] bytes_from_point(BigInteger[] point) {
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byte[] res=new byte[33];
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res[0]=BigInteger.ONE.compareTo(point[1].and(BigInteger.ONE))==0 ? (byte)0x03 : (byte)0x02;
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System.arraycopy(to32BytesData(point[0]), 0, res, 1, 32);
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return res;
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}
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public static byte[] schnorr_sign(byte[] msg, BigInteger seckey) {
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if(msg.length!=32)
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throw new RuntimeException("The message must be a 32-byte array.");
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if(BigInteger.ZERO.compareTo(seckey)>0 || seckey.compareTo(n.subtract(BigInteger.ONE)) >0)
108+
throw new RuntimeException("The secret key must be an integer in the range 1..n-1.");
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byte[] resultData=new byte[32+msg.length];
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System.arraycopy(to32BytesData(seckey), 0, resultData, 0, 32);
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System.arraycopy(msg, 0, resultData, 32, msg.length);
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try {
115+
BigInteger k0=toBigInteger(sha256(resultData)).mod(n);
116+
if(BigInteger.ZERO.compareTo(k0)==0)
117+
throw new RuntimeException("Failure. This happens only with negligible probability.");
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BigInteger[] R = point_mul(G, k0);
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BigInteger k=BigInteger.ONE.compareTo(jacobi(R[1]))!=0 ? n.subtract(k0) : k0;
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byte[] R0Bytes=to32BytesData(R[0]);
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byte[] eData=new byte[32+33+32];
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System.arraycopy(R0Bytes, 0, eData, 0, 32);
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System.arraycopy(bytes_from_point(point_mul(G, seckey)), 0, eData, 32, 33);
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System.arraycopy(msg, 0, eData, 65, 32);
127+
eData=sha256(eData);
128+
BigInteger e=toBigInteger(eData).mod(n);
129+
130+
byte[] finalData=new byte[64];
131+
System.arraycopy(R0Bytes, 0, finalData, 0, 32);
132+
System.arraycopy(to32BytesData(e.multiply(seckey).add(k).mod(n)), 0, finalData, 32, 32);
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134+
return finalData;
135+
} catch(Exception e) {
136+
e.printStackTrace();
137+
throw new RuntimeException("Error occurs during schnorr_sign, e="+e);
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}
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}
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public static boolean schnorr_verify(byte[] msg, byte[] pubkey, byte[] sig) {
142+
if(msg.length!=32)
143+
throw new RuntimeException("The message must be a 32-byte array.");
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145+
if(pubkey.length!=33)
146+
throw new RuntimeException("The public key must be a 33-byte array.");
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148+
if(sig.length!=64)
149+
throw new RuntimeException("The signature must be a 64-byte array.");
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BigInteger[] P = point_from_bytes(pubkey);
152+
if(P==null)
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return false;
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BigInteger r=toBigInteger(sig,0,32);
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BigInteger s=toBigInteger(sig,32,32);
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158+
if(r.compareTo(p)>=0 || s.compareTo(n)>=0)
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return false;
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try {
162+
byte[] eData=new byte[32+33+32];
163+
System.arraycopy(sig, 0, eData, 0, 32);
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System.arraycopy(bytes_from_point(P), 0, eData, 32, 33);
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System.arraycopy(msg, 0, eData, 65, 32);
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eData=sha256(eData);
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BigInteger e=toBigInteger(eData).mod(n);
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BigInteger[] R=point_add(point_mul(G, s), point_mul(P, n.subtract(e)));
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if(R==null || BigInteger.ONE.compareTo(jacobi(R[1]))!=0 || r.compareTo(R[0])!=0)
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return false;
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return true;
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} catch(Exception e) {
175+
e.printStackTrace();
176+
throw new RuntimeException("Error occurs during schnorr_verify, e="+e);
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}
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}
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public static byte[] hexStringToByteArray(String s) {
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int len = s.length();
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byte[] data = new byte[len / 2];
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for (int i = 0; i < len; i += 2) {
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data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
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+ Character.digit(s.charAt(i+1), 16));
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}
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return data;
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}
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public static String bytesToHex(byte[] bytes) {
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char[] hexChars = new char[bytes.length * 2];
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for ( int j = 0; j < bytes.length; j++ ) {
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int v = bytes[j] & 0xFF;
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hexChars[j * 2] = hexArray[v >>> 4];
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hexChars[j * 2 + 1] = hexArray[v & 0x0F];
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}
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return new String(hexChars);
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}
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public static String bytesToHex(byte[] bytes, int startPos, int len) {
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char[] hexChars = new char[len * 2];
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for ( int j = 0, i=startPos; j < len; j++, i++ ) {
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int v = bytes[i] & 0xFF;
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hexChars[j * 2] = hexArray[v >>> 4];
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hexChars[j * 2 + 1] = hexArray[v & 0x0F];
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}
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return new String(hexChars);
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}
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public static byte[] sha256(byte[] input) throws NoSuchAlgorithmException {
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MessageDigest digest = MessageDigest.getInstance("SHA-256");
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return digest.digest(input);
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}
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}

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