simple rerandomize test

gradle/wrapper/gradle-wrapper.properties

@@ -1,4 +1,4 @@
-#Sun Dec 27 09:28:01 IST 2015
+#Sun Mar 20 15:13:00 IST 2016
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME

mixer/src/test/java/mixer/CreateTestVector.java

@@ -68,7 +68,7 @@ public class CreateTestVector {
         }
         return result;
     }
-    //@Test
+    //@SimpleRerandomizeTest
     public void createValidTest() throws IOException {
 
         List<Crypto.RerandomizableEncryptedMessage> mixerInput = generateMixerInput();
@@ -81,7 +81,7 @@ public class CreateTestVector {
         System.out.println("all done");
     }
 
-    //@Test
+    //@SimpleRerandomizeTest
     public void createInvalidTest() throws IOException {
 
         //Mix2ZeroKnowledgeVerifier corruptedVerifier = new Verifier(encryptor,randomOracle,true);

mixer/src/test/java/mixer/RerandomizeTest.java

@@ -62,10 +62,18 @@ public class RerandomizeTest {
         ConcreteCrypto.ElGamalCiphertext eElGamal = ECElGamalEncryption.RerandomizableEncryptedMessage2ElGamalCiphertext(e);
         ConcreteCrypto.ElGamalCiphertext eNewElGamal = ECElGamalEncryption.RerandomizableEncryptedMessage2ElGamalCiphertext(eNew);
 
-        assert (g.multiply(new BigInteger(r.getData().toByteArray())).equals(
+        ECPoint expected1 = g.multiply(new BigInteger(r.getData().toByteArray()));
-               group.add(convert2ECPoint(eNewElGamal.getC1()),group.negate(convert2ECPoint(eElGamal.getC1())))));
+        ECPoint result1 = group.add(convert2ECPoint(eNewElGamal.getC1()),group.negate(convert2ECPoint(eElGamal.getC1())));
-        assert(h.multiply(new BigInteger(r.getData().toByteArray())).equals(
+        expected1.normalize();
-                group.add(convert2ECPoint(eNewElGamal.getC2()), group.negate(convert2ECPoint(eElGamal.getC2())))));
+        result1.normalize();
+        assert (expected1.equals(result1));
+
+        ECPoint expected2 = h.multiply(new BigInteger(r.getData().toByteArray()));
+        ECPoint result2 = group.add(convert2ECPoint(eNewElGamal.getC2()), group.negate(convert2ECPoint(eElGamal.getC2())));
+        expected2.normalize();
+        result2.normalize();
+
+        assert (expected2.equals(result2));
     }
 
     @Test

mixer/src/test/java/mixer/SimpleRerandomizeTest.java

@@ -0,0 +1,89 @@
+package mixer;
+
+import org.bouncycastle.math.ec.ECPoint;
+import org.junit.Before;
+import qilin.primitives.concrete.ECGroup;
+
+import java.math.BigInteger;
+import java.util.Random;
+
+/**
+ * Created by Tzlil on 3/20/2016.
+ */
+public class SimpleRerandomizeTest {
+
+    Random rand;
+    ECGroup group;
+    ECPoint g ;
+    ECPoint h ;
+    BigInteger sk;
+    @Before
+    public void setup() throws Exception {
+        rand = new Random();
+        group = new ECGroup("secp256k1");
+        g = group.getGenerator();
+        sk = random();
+        h = g.multiply(sk);
+    }
+
+    public BigInteger random(){
+        return new BigInteger(256,rand).mod(group.orderUpperBound());
+    }
+
+    public ECPoint randomMessage(){
+        return group.sample(rand);
+    }
+
+    public Encryption encrypt(ECPoint message,BigInteger randomness){
+        return new Encryption(g.multiply(randomness), message.add(h.multiply(randomness)));
+    }
+
+    public Encryption rerandomize(Encryption encryption,BigInteger randomness){
+        return new Encryption(encryption.a.add(g.multiply(randomness)),encryption.b.add(h.multiply(randomness)));
+    }
+
+    public ECPoint decrypt(Encryption encryption){
+        return encryption.a.multiply(sk).negate().add(encryption.b);
+    }
+
+    public class Encryption{
+        ECPoint a,b;
+        Encryption(ECPoint a, ECPoint b){
+            this.a = a;
+            this.b = b;
+        }
+    }
+
+    public void oneRerandomizeTest(){
+        ECPoint message = randomMessage();
+        Encryption e = encrypt(message,random());
+        BigInteger r = random();
+        Encryption eNew = rerandomize(e,r);
+        assert (decrypt(e).equals(message));
+        assert (decrypt(eNew).equals(message));
+
+        ECPoint expected1 = g.multiply(r);
+        ECPoint result1 = group.add(eNew.a,e.a.negate());
+        expected1.normalize();
+        result1.normalize();
+        assert (expected1.equals(result1));
+
+        ECPoint expected2 = h.multiply(r);
+        ECPoint result2 = group.add(eNew.b,e.b.negate());
+        expected2.normalize();
+        result2.normalize();
+        assert (expected2.equals(result2));
+    }
+
+
+    @org.junit.Test
+    public void rerandomizeTest(){
+
+        int tests = 1000;
+
+        for (int i = 0; i < tests; i ++){
+            System.out.println("rerandomize test #" + i);
+            oneRerandomizeTest();
+        }
+    }
+}