bcgit · timw · Jul 6, 2013 · Jul 6, 2013 · Jul 7, 2013 · Jul 7, 2013
diff --git a/core/src/main/java/org/bouncycastle/crypto/engines/ChaChaEngine.java b/core/src/main/java/org/bouncycastle/crypto/engines/ChaChaEngine.java
@@ -0,0 +1,186 @@
+package org.bouncycastle.crypto.engines;
+
+import org.bouncycastle.crypto.util.Pack;
+
+/**
+ * Implementation of Daniel J. Bernstein's ChaCha stream cipher.
+ */
+public class ChaChaEngine extends Salsa20Engine
+{
+
+    /**
+     * Creates a 20 rounds ChaCha engine.
+     */
+    public ChaChaEngine()
+    {
+        super();
+    }
+
+    /**
+     * Creates a ChaCha engine with a specific number of rounds.
+     * @param rounds the number of rounds (must be an even number).
+     */
+    public ChaChaEngine(int rounds)
+    {
+        super(rounds);
+    }
+
+    public String getAlgorithmName()
+    {
+        return "ChaCha" + rounds;
+    }
+
+    protected void advanceCounter()
+    {
+        if (++engineState[12] == 0)
+        {
+            ++engineState[13];
+        }
+    }
+
+    protected void resetCounter()
+    {
+        engineState[12] = engineState[13] = 0;
+    }
+
+    protected void setKey(byte[] keyBytes, byte[] ivBytes)
+    {
+        if ((keyBytes.length != 16) && (keyBytes.length != 32))
+        {
+            throw new IllegalArgumentException(getAlgorithmName() + " requires 128 bit or 256 bit key");
+        }
+
+        int offset = 0;
+        byte[] constants;
+
+        // Key
+        engineState[4] = Pack.littleEndianToInt(keyBytes, 0);
+        engineState[5] = Pack.littleEndianToInt(keyBytes, 4);
+        engineState[6] = Pack.littleEndianToInt(keyBytes, 8);
+        engineState[7] = Pack.littleEndianToInt(keyBytes, 12);
+
+        if (keyBytes.length == 32)
+        {
+            constants = sigma;
+            offset = 16;
+        } else
+        {
+            constants = tau;
+        }
+
+        engineState[8] = Pack.littleEndianToInt(keyBytes, offset);
+        engineState[9] = Pack.littleEndianToInt(keyBytes, offset + 4);
+        engineState[10] = Pack.littleEndianToInt(keyBytes, offset + 8);
+        engineState[11] = Pack.littleEndianToInt(keyBytes, offset + 12);
+
+        engineState[0] = Pack.littleEndianToInt(constants, 0);
+        engineState[1] = Pack.littleEndianToInt(constants, 4);
+        engineState[2] = Pack.littleEndianToInt(constants, 8);
+        engineState[3] = Pack.littleEndianToInt(constants, 12);
+
+        // Counter
+        engineState[12] = engineState[13] = 0;
+
+        // IV
+        engineState[14] = Pack.littleEndianToInt(ivBytes, 0);
+        engineState[15] = Pack.littleEndianToInt(ivBytes, 4);
+    }
+
+    protected void generateKeyStream(byte[] output)
+    {
+        chachaCore(rounds, engineState, x);
+        Pack.intToLittleEndian(x, output, 0);
+    }
+
+    /**
+     * ChacCha function
+     *
+     * @param   input   input data
+     *
+     * @return  keystream
+     */    
+    public static void chachaCore(int rounds, int[] input, int[] x)
+    {
+        if (input.length != 16) {
+            throw new IllegalArgumentException();
+        }
+        if (x.length != 16) {
+            throw new IllegalArgumentException();
+        }
+        if (rounds % 2 != 0) {
+            throw new IllegalArgumentException("Number of rounds must be even");
+        }
+
+        int x00 = input[ 0];
+        int x01 = input[ 1];
+        int x02 = input[ 2];
+        int x03 = input[ 3];
+        int x04 = input[ 4];
+        int x05 = input[ 5];
+        int x06 = input[ 6];
+        int x07 = input[ 7];
+        int x08 = input[ 8];
+        int x09 = input[ 9];
+        int x10 = input[10];
+        int x11 = input[11];
+        int x12 = input[12];
+        int x13 = input[13];
+        int x14 = input[14];
+        int x15 = input[15];
+
+        for (int i = rounds; i > 0; i -= 2)
+        {
+            x00 += x04; x12 = rotl(x12 ^ x00, 16);
+            x08 += x12; x04 = rotl(x04 ^ x08, 12);
+            x00 += x04; x12 = rotl(x12 ^ x00, 8);
+            x08 += x12; x04 = rotl(x04 ^ x08, 7);
+            x01 += x05; x13 = rotl(x13 ^ x01, 16);
+            x09 += x13; x05 = rotl(x05 ^ x09, 12);
+            x01 += x05; x13 = rotl(x13 ^ x01, 8);
+            x09 += x13; x05 = rotl(x05 ^ x09, 7);
+            x02 += x06; x14 = rotl(x14 ^ x02, 16);
+            x10 += x14; x06 = rotl(x06 ^ x10, 12);
+            x02 += x06; x14 = rotl(x14 ^ x02, 8);
+            x10 += x14; x06 = rotl(x06 ^ x10, 7);
+            x03 += x07; x15 = rotl(x15 ^ x03, 16);
+            x11 += x15; x07 = rotl(x07 ^ x11, 12);
+            x03 += x07; x15 = rotl(x15 ^ x03, 8);
+            x11 += x15; x07 = rotl(x07 ^ x11, 7);
+            x00 += x05; x15 = rotl(x15 ^ x00, 16);
+            x10 += x15; x05 = rotl(x05 ^ x10, 12);
+            x00 += x05; x15 = rotl(x15 ^ x00, 8);
+            x10 += x15; x05 = rotl(x05 ^ x10, 7);
+            x01 += x06; x12 = rotl(x12 ^ x01, 16);
+            x11 += x12; x06 = rotl(x06 ^ x11, 12);
+            x01 += x06; x12 = rotl(x12 ^ x01, 8);
+            x11 += x12; x06 = rotl(x06 ^ x11, 7);
+            x02 += x07; x13 = rotl(x13 ^ x02, 16);
+            x08 += x13; x07 = rotl(x07 ^ x08, 12);
+            x02 += x07; x13 = rotl(x13 ^ x02, 8);
+            x08 += x13; x07 = rotl(x07 ^ x08, 7);
+            x03 += x04; x14 = rotl(x14 ^ x03, 16);
+            x09 += x14; x04 = rotl(x04 ^ x09, 12);
+            x03 += x04; x14 = rotl(x14 ^ x03, 8);
+            x09 += x14; x04 = rotl(x04 ^ x09, 7);
+
+        }
+
+        x[ 0] = x00 + input[ 0];
+        x[ 1] = x01 + input[ 1];
+        x[ 2] = x02 + input[ 2];
+        x[ 3] = x03 + input[ 3];
+        x[ 4] = x04 + input[ 4];
+        x[ 5] = x05 + input[ 5];
+        x[ 6] = x06 + input[ 6];
+        x[ 7] = x07 + input[ 7];
+        x[ 8] = x08 + input[ 8];
+        x[ 9] = x09 + input[ 9];
+        x[10] = x10 + input[10];
+        x[11] = x11 + input[11];
+        x[12] = x12 + input[12];
+        x[13] = x13 + input[13];
+        x[14] = x14 + input[14];
+        x[15] = x15 + input[15];
+    }
+
+}