1 files changed, 38 insertions, 3 deletions
diff --git a/src/cz/crcs/ectester/common/util/ECUtil.java b/src/cz/crcs/ectester/common/util/ECUtil.java
index 1706ca0..0260e95 100644
--- a/src/cz/crcs/ectester/common/util/ECUtil.java
+++ b/src/cz/crcs/ectester/common/util/ECUtil.java
@@ -3,9 +3,16 @@ package cz.crcs.ectester.common.util;
 import cz.crcs.ectester.applet.EC_Consts;
 import cz.crcs.ectester.common.ec.*;
 import cz.crcs.ectester.data.EC_Store;
+import org.bouncycastle.asn1.ASN1Integer;
+import org.bouncycastle.asn1.ASN1StreamParser;
+import org.bouncycastle.asn1.DERSequence;
+import org.bouncycastle.asn1.DERSequenceParser;
 
+import java.io.IOException;
 import java.math.BigInteger;
 import java.security.KeyPair;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
 import java.security.interfaces.ECPrivateKey;
 import java.security.interfaces.ECPublicKey;
 import java.security.spec.*;
@@ -196,7 +203,7 @@ public class ECUtil {
     public static ECPublicKey toPublicKey(EC_Key.Public pubkey) {
         EC_Curve curve = EC_Store.getInstance().getObject(EC_Curve.class, pubkey.getCurve());
         if (curve == null) {
-            throw new IllegalArgumentException("pubkey curve nor found: " + pubkey.getCurve());
+            throw new IllegalArgumentException("pubkey curve not found: " + pubkey.getCurve());
         }
         return new RawECPublicKey(toPoint(pubkey), curve.toSpec());
     }
@@ -204,7 +211,7 @@ public class ECUtil {
     public static ECPrivateKey toPrivateKey(EC_Key.Private privkey) {
         EC_Curve curve = EC_Store.getInstance().getObject(EC_Curve.class, privkey.getCurve());
         if (curve == null) {
-            throw new IllegalArgumentException("privkey curve nor found: " + privkey.getCurve());
+            throw new IllegalArgumentException("privkey curve not found: " + privkey.getCurve());
         }
         return new RawECPrivateKey(toScalar(privkey), curve.toSpec());
     }
@@ -212,7 +219,7 @@ public class ECUtil {
     public static KeyPair toKeyPair(EC_Keypair kp) {
         EC_Curve curve = EC_Store.getInstance().getObject(EC_Curve.class, kp.getCurve());
         if (curve == null) {
-            throw new IllegalArgumentException("keypair curve nor found: " + kp.getCurve());
+            throw new IllegalArgumentException("keypair curve not found: " + kp.getCurve());
         }
         ECPublicKey pubkey = new RawECPublicKey(toPoint(kp), curve.toSpec());
         ECPrivateKey privkey = new RawECPrivateKey(toScalar(kp), curve.toSpec());
@@ -222,4 +229,32 @@ public class ECUtil {
     public static byte[] toDERSignature(byte[] r, byte[] s) {
         return ByteUtil.concatenate(new byte[]{0x30, (byte) (r.length + s.length + 4), 0x02, (byte) r.length}, r, new byte[]{0x02, (byte) s.length}, s);
     }
+
+    public static BigInteger[] fromDERSignature(byte[] signature) throws IOException {
+        ASN1StreamParser parser = new ASN1StreamParser(signature);
+        DERSequence sequence = (DERSequence) ((DERSequenceParser) parser.readObject()).getLoadedObject();
+        ASN1Integer r = (ASN1Integer) sequence.getObjectAt(0);
+        ASN1Integer s = (ASN1Integer) sequence.getObjectAt(1);
+        return new BigInteger[]{r.getPositiveValue(), s.getPositiveValue()};
+    }
+
+    public static BigInteger recoverSignatureNonce(byte[] signature, byte[] data, BigInteger privkey, ECParameterSpec params, String hashType) {
+        try {
+            int bitSize = params.getOrder().bitLength();
+            MessageDigest md = MessageDigest.getInstance(hashType);
+            byte[] hash = md.digest(data);
+            BigInteger hashInt = new BigInteger(1, hash);
+            hashInt = hashInt.and(BigInteger.ONE.shiftLeft(bitSize + 1).subtract(BigInteger.ONE));
+
+            BigInteger[] sigPair = fromDERSignature(signature);
+            BigInteger r = sigPair[0];
+            BigInteger s = sigPair[1];
+
+            BigInteger rd = privkey.multiply(r).mod(params.getOrder());
+            BigInteger hrd = hashInt.add(rd).mod(params.getOrder());
+            return s.modInverse(params.getOrder()).multiply(hrd).mod(params.getOrder());
+        } catch (NoSuchAlgorithmException | IOException nsae) {
+            return null;
+        }
+    }
 }