1 files changed, 144 insertions, 0 deletions
diff --git a/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/engines/RC4Engine.java b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/engines/RC4Engine.java
new file mode 100644
index 000000000..712426f1e
--- /dev/null
+++ b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/engines/RC4Engine.java
@@ -0,0 +1,144 @@
+package org.spongycastle.crypto.engines;
+
+import org.spongycastle.crypto.CipherParameters;
+import org.spongycastle.crypto.DataLengthException;
+import org.spongycastle.crypto.OutputLengthException;
+import org.spongycastle.crypto.StreamCipher;
+import org.spongycastle.crypto.params.KeyParameter;
+
+public class RC4Engine implements StreamCipher
+{
+    private final static int STATE_LENGTH = 256;
+
+    /*
+     * variables to hold the state of the RC4 engine
+     * during encryption and decryption
+     */
+
+    private byte[]      engineState = null;
+    private int         x = 0;
+    private int         y = 0;
+    private byte[]      workingKey = null;
+
+    /**
+     * initialise a RC4 cipher.
+     *
+     * @param forEncryption whether or not we are for encryption.
+     * @param params the parameters required to set up the cipher.
+     * @exception IllegalArgumentException if the params argument is
+     * inappropriate.
+     */
+    public void init(
+        boolean             forEncryption, 
+        CipherParameters     params
+   )
+    {
+        if (params instanceof KeyParameter)
+        {
+            /* 
+             * RC4 encryption and decryption is completely
+             * symmetrical, so the 'forEncryption' is 
+             * irrelevant.
+             */
+            workingKey = ((KeyParameter)params).getKey();
+            setKey(workingKey);
+
+            return;
+        }
+
+        throw new IllegalArgumentException("invalid parameter passed to RC4 init - " + params.getClass().getName());
+    }
+
+    public String getAlgorithmName()
+    {
+        return "RC4";
+    }
+
+    public byte returnByte(byte in)
+    {
+        x = (x + 1) & 0xff;
+        y = (engineState[x] + y) & 0xff;
+
+        // swap
+        byte tmp = engineState[x];
+        engineState[x] = engineState[y];
+        engineState[y] = tmp;
+
+        // xor
+        return (byte)(in ^ engineState[(engineState[x] + engineState[y]) & 0xff]);
+    }
+
+    public void processBytes(
+        byte[]     in, 
+        int     inOff, 
+        int     len, 
+        byte[]     out, 
+        int     outOff)
+    {
+        if ((inOff + len) > in.length)
+        {
+            throw new DataLengthException("input buffer too short");
+        }
+
+        if ((outOff + len) > out.length)
+        {
+            throw new OutputLengthException("output buffer too short");
+        }
+
+        for (int i = 0; i < len ; i++)
+        {
+            x = (x + 1) & 0xff;
+            y = (engineState[x] + y) & 0xff;
+
+            // swap
+            byte tmp = engineState[x];
+            engineState[x] = engineState[y];
+            engineState[y] = tmp;
+
+            // xor
+            out[i+outOff] = (byte)(in[i + inOff]
+                    ^ engineState[(engineState[x] + engineState[y]) & 0xff]);
+        }
+    }
+
+    public void reset()
+    {
+        setKey(workingKey);
+    }
+
+    // Private implementation
+
+    private void setKey(byte[] keyBytes)
+    {
+        workingKey = keyBytes;
+
+        // System.out.println("the key length is ; "+ workingKey.length);
+
+        x = 0;
+        y = 0;
+
+        if (engineState == null)
+        {
+            engineState = new byte[STATE_LENGTH];
+        }
+
+        // reset the state of the engine
+        for (int i=0; i < STATE_LENGTH; i++)
+        {
+            engineState[i] = (byte)i;
+        }
+        
+        int i1 = 0;
+        int i2 = 0;
+
+        for (int i=0; i < STATE_LENGTH; i++)
+        {
+            i2 = ((keyBytes[i1] & 0xff) + engineState[i] + i2) & 0xff;
+            // do the byte-swap inline
+            byte tmp = engineState[i];
+            engineState[i] = engineState[i2];
+            engineState[i2] = tmp;
+            i1 = (i1+1) % keyBytes.length; 
+        }
+    }
+}