1 files changed, 142 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/crypto/engines/VMPCEngine.java b/core/src/main/java/org/spongycastle/crypto/engines/VMPCEngine.java
new file mode 100644
index 00000000..f1a4a564
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/crypto/engines/VMPCEngine.java
@@ -0,0 +1,142 @@
+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;
+import org.spongycastle.crypto.params.ParametersWithIV;
+
+public class VMPCEngine implements StreamCipher
+{
+    /*
+     * variables to hold the state of the VMPC engine during encryption and
+     * decryption
+     */
+    protected byte n = 0;
+    protected byte[] P = null;
+    protected byte s = 0;
+
+    protected byte[] workingIV;
+    protected byte[] workingKey;
+
+    public String getAlgorithmName()
+    {
+        return "VMPC";
+    }
+
+    /**
+     * initialise a VMPC 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 ParametersWithIV))
+        {
+            throw new IllegalArgumentException(
+                "VMPC init parameters must include an IV");
+        }
+
+        ParametersWithIV ivParams = (ParametersWithIV) params;
+
+        if (!(ivParams.getParameters() instanceof KeyParameter))
+        {
+            throw new IllegalArgumentException(
+                "VMPC init parameters must include a key");
+        }
+
+        KeyParameter key = (KeyParameter) ivParams.getParameters();
+
+        this.workingIV = ivParams.getIV();
+
+        if (workingIV == null || workingIV.length < 1 || workingIV.length > 768)
+        {
+            throw new IllegalArgumentException("VMPC requires 1 to 768 bytes of IV");
+        }
+
+        this.workingKey = key.getKey();
+
+        initKey(this.workingKey, this.workingIV);
+    }
+
+    protected void initKey(byte[] keyBytes, byte[] ivBytes)
+    {
+        s = 0;
+        P = new byte[256];
+        for (int i = 0; i < 256; i++)
+        {
+            P[i] = (byte) i;
+        }
+
+        for (int m = 0; m < 768; m++)
+        {
+            s = P[(s + P[m & 0xff] + keyBytes[m % keyBytes.length]) & 0xff];
+            byte temp = P[m & 0xff];
+            P[m & 0xff] = P[s & 0xff];
+            P[s & 0xff] = temp;
+        }
+        for (int m = 0; m < 768; m++)
+        {
+            s = P[(s + P[m & 0xff] + ivBytes[m % ivBytes.length]) & 0xff];
+            byte temp = P[m & 0xff];
+            P[m & 0xff] = P[s & 0xff];
+            P[s & 0xff] = temp;
+        }
+        n = 0;
+    }
+
+    public int 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++)
+        {
+            s = P[(s + P[n & 0xff]) & 0xff];
+            byte z = P[(P[(P[s & 0xff]) & 0xff] + 1) & 0xff];
+            // encryption
+            byte temp = P[n & 0xff];
+            P[n & 0xff] = P[s & 0xff];
+            P[s & 0xff] = temp;
+            n = (byte) ((n + 1) & 0xff);
+
+            // xor
+            out[i + outOff] = (byte) (in[i + inOff] ^ z);
+        }
+
+        return len;
+    }
+
+    public void reset()
+    {
+        initKey(this.workingKey, this.workingIV);
+    }
+
+    public byte returnByte(byte in)
+    {
+        s = P[(s + P[n & 0xff]) & 0xff];
+        byte z = P[(P[(P[s & 0xff]) & 0xff] + 1) & 0xff];
+        // encryption
+        byte temp = P[n & 0xff];
+        P[n & 0xff] = P[s & 0xff];
+        P[s & 0xff] = temp;
+        n = (byte) ((n + 1) & 0xff);
+
+        // xor
+        return (byte) (in ^ z);
+    }
+}