updated mixer code

mixer/src/main/java/mixer/Graph.java

@@ -10,7 +10,7 @@ class Graph
 	private Node[] nodes;
 	protected Graph(int[] permutation){
 		n = permutation.length; // n = 2^k
-        nDiv2 = n /2;
+        nDiv2 = n >> 1;
         createNodes();
         createEdges(permutation);
         setSwitches();

mixer/src/main/java/mixer/Mixer.java

@@ -6,6 +6,8 @@ import java.util.Queue;
 import java.util.concurrent.ArrayBlockingQueue;
 import javafx.util.Pair;
 import java.util.Random;
+import java.util.regex.Matcher;
+
 import com.google.protobuf.InvalidProtocolBufferException;
 
 import meerkat.protobuf.Crypto.*;
@@ -30,41 +32,38 @@ public class Mixer implements meerkat.crypto.mixnet.Mixer{
 	public Pair<ZeroKnowledgeProof[][],RerandomizableEncryptedMessage[][]> mix(List<RerandomizableEncryptedMessage> ciphertexts) throws InvalidProtocolBufferException{
 
 		int n = ciphertexts.size();
+		int nDiv2 = n >> 1;
 		// assert n = 2^k and n > 1
 		if( n <= 1 || ((n & (n-1)) != 0))
 			return null;
 
 		//initialization
-		int layers = 0;
+		int layers = (int)(2 * Math.log(n)/Math.log(2)) - 1;  // layers = 2logn -1
-		for (int i = n; i > 1; i>>=1) {
-			layers++;
-		}
-        layers<<=1;
-        layers--;
         RerandomizableEncryptedMessage[][] encryptionTable = new RerandomizableEncryptedMessage[layers][n];
-    	ZeroKnowledgeProof[][] proofsTable= new ZeroKnowledgeProof[layers][n/2];
+    	ZeroKnowledgeProof[][] proofsTable= new ZeroKnowledgeProof[layers][nDiv2];
 		boolean[][] mixnet = createMixNet(n,layers);
         int index1, index2, switchIndex = 0;
         EncryptionRandomness r1 ,r2;
         RerandomizableEncryptedMessage e1, e2;
         boolean half = true;
         
-        //set first level of encryption
+        // set first level of encryption
         for (int j = 0; j < n; j++)
         {
             encryptionTable[0][j] = ciphertexts.get(j);
         }
 
         // main loop
-		int i = n;
+		int i = n,iDiv2;
         for (int layer = 0; layer < layers; layer++) // i == permutation size
         {
+			iDiv2 = i >> 1;
             for (int j = 0; j < n; j += i) // j == permutation index
             {
-                for (int k = 0; k < i / 2; k++) // k == elements index in permutation j
+                for (int k = 0; k < iDiv2; k++) // k == elements index in permutation j
                 {
                     index1 = k + j;
-                    index2 = k + j + i / 2;
+                    index2 = k + j + iDiv2;
                     e1 = encryptionTable[layer][index1];
                     e2 = encryptionTable[layer][index2];
                     r1 = encryptor.generateRandomness(random);
@@ -85,12 +84,12 @@ public class Mixer implements meerkat.crypto.mixnet.Mixer{
                     				encryptionTable[layer + 1][index2],
                     				 mixnet[layer][switchIndex], r1,r2);
                     
-                    switchIndex = (switchIndex + 1) % (n / 2);
+                    switchIndex = (switchIndex + 1) % nDiv2;
                 }
             }
             if (half)
             {
-                i >>= 1;
+                i = iDiv2;
                 if (i == 1)
                 {
                     half = false;
@@ -127,32 +126,34 @@ public class Mixer implements meerkat.crypto.mixnet.Mixer{
 		int[] pi, piL, piR;
 		Queue<int[]> permutationsQueue = new ArrayBlockingQueue<int[]>(n);
 		Graph graph;
-		boolean[][] mixnet = new boolean[layers][n>>1];
+		int iDiv2;
+		int nDiv2 = n >> 1;
+		boolean[][] mixnet = new boolean[layers][nDiv2];
 
 		permutationsQueue.add(permutation);
-
 		for (int i = n, layer = 0; i > 1; i >>= 1, layer++) // i == permutation size
 		{
-			for (int j = 0; j < n / 2; j += i / 2) // j == permutation index
+			iDiv2 = i >> 1;
+			for (int j = 0; j < nDiv2; j += iDiv2) // j == permutation index
 			{
 				pi = permutationsQueue.remove();
 				graph = new Graph(pi);
-				piL = new int[i / 2];
+				piL = new int[iDiv2];
-				piR = new int[i / 2];
+				piR = new int[iDiv2];
-				for (int k = 0; k < i / 2; k++) // k == switch index in permutation j
+				for (int k = 0; k < iDiv2; k++) // k == switch index in permutation j
 				{
 					mixnet[layers - layer - 1][k + j] = graph.getSwitchValue(k, true);
 					mixnet[layer][k + j] = graph.getSwitchValue(k, false);
 
 					if (!mixnet[layers - layer - 1][k + j])
 					{
-						piL[k] = pi[k] % (i / 2);
+						piL[k] = pi[k] % iDiv2;
-						piR[k] = pi[k + i / 2] % (i / 2);
+						piR[k] = pi[k + iDiv2] % iDiv2;
 					}
 					else
 					{
-						piL[k] = pi[k + i / 2] % (i / 2);
+						piL[k] = pi[k + iDiv2] % iDiv2;
-						piR[k] = pi[k] % (i / 2);
+						piR[k] = pi[k] % iDiv2;
 					}
 				}
 				permutationsQueue.add(piL);