Utility functions added

Functions for easier Signature computation, transaction hash computation, signature verification

lib_btc.js

@@ -2205,6 +2205,63 @@
                 return Crypto.util.bytesToHex(buffer);
             }
             
+            //Utility funtion added to directly compute signatures without transaction index
+            r.transactionSigNoIndex = function(wif, sigHashType, txhash){
+
+			function serializeSig(r, s) {
+				var rBa = r.toByteArraySigned();
+				var sBa = s.toByteArraySigned();
+
+				var sequence = [];
+				sequence.push(0x02); // INTEGER
+				sequence.push(rBa.length);
+				sequence = sequence.concat(rBa);
+
+				sequence.push(0x02); // INTEGER
+				sequence.push(sBa.length);
+				sequence = sequence.concat(sBa);
+
+				sequence.unshift(sequence.length);
+				sequence.unshift(0x30); // SEQUENCE
+
+				return sequence;
+			}
+
+			var shType = sigHashType || 1;
+			var hash = Crypto.util.hexToBytes(txhash);
+
+			if(hash){
+				var curve = EllipticCurve.getSECCurveByName("secp256k1");
+				var key = coinjs.wif2privkey(wif);
+				var priv = BigInteger.fromByteArrayUnsigned(Crypto.util.hexToBytes(key['privkey']));
+				var n = curve.getN();
+				var e = BigInteger.fromByteArrayUnsigned(hash);
+
+				var badrs = 0
+				do {
+					var k = this.deterministicK(wif, hash, badrs);
+					var G = curve.getG();
+					var Q = G.multiply(k);
+					var r = Q.getX().toBigInteger().mod(n);
+					var s = k.modInverse(n).multiply(e.add(priv.multiply(r))).mod(n);
+					badrs++
+				} while (r.compareTo(BigInteger.ZERO) <= 0 || s.compareTo(BigInteger.ZERO) <= 0);
+
+				// Force lower s values per BIP62
+				var halfn = n.shiftRight(1);
+				if (s.compareTo(halfn) > 0) {
+					s = n.subtract(s);
+				};
+
+				var sig = serializeSig(r, s);
+				sig.push(parseInt(shType, 10));
+
+				return Crypto.util.bytesToHex(sig);
+			} else {
+				return false;
+			    }
+		    } 
+
             /* deserialize a transaction */
             r.deserialize = function (buffer) {
                 if (typeof buffer == "string") {
@@ -2734,6 +2791,53 @@
         return coinjs.bech32_encode(hrp, bytes);
     }
    
+    //Five utility functions added for generating transaction hashes and verification of signatures
+    var changeEndianness = (string) => {
+        const result = [];
+        let len = string.length - 2;
+        while (len >= 0) {
+          result.push(string.substr(len, 2));
+          len -= 2;
+        }
+        return result.join('');
+        }
+
+    function getTransactionHash(transaction_in_hex) {
+        var x1,x2,x3,x4,x5;
+        x1 = Crypto.util.hexToBytes(transaction_in_hex);
+        x2 = Crypto.SHA256(x1);
+        x3 = Crypto.util.hexToBytes(x2);
+        x4 = Crypto.SHA256(x3);
+        x5 = changeEndianness(x4);
+        return x5;
+        }    
+
+    function compressedToUncompressed(compressed) {
+        var t1,t2;
+        t1 = curve.curve.decodePointHex(compressed);
+        t2 = curve.curve.encodePointHex(t1);
+        return t2;
+        }
+
+    function uncompressedToCompressed(uncompressed) {
+        var t1,t2,t3;
+        t1 = uncompressed.charAt(uncompressed.length-1)
+        t2 = parseInt(t1,10);
+        //Check if the last digit is odd
+        if(t2 % 2 == 1) { t3 = "03";} else { t3 = "02" };
+        return t3+ uncompressed.substr(2,64);
+    }
+    
+   function verifySignatureHex(hashHex,sigHex,pubHexCompressed){
+        var h1,s1,p1,p2;
+        h1 = Crypto.util.hexToBytes(hashHex);
+        s1 = Crypto.util.hexToBytes(sigHex);
+        p1 = compressedToUncompressed(pubHexCompressed);
+        p2 = Crypto.util.hexToBytes(p1);
+        
+        return coinjs.verifySignature(h1,s1,p2);
+        }
+    
     btc_api.getBalance = addr => new Promise((resolve, reject) => {
         fetch_api(`get_address_balance/BTC/${addr}`)
             .then(result => resolve(parseFloat(result.data.confirmed_balance)))