1 files changed, 113 insertions, 0 deletions
diff --git a/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/modes/SICBlockCipher.java b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/modes/SICBlockCipher.java
new file mode 100644
index 000000000..f228baf35
--- /dev/null
+++ b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/modes/SICBlockCipher.java
@@ -0,0 +1,113 @@
+package org.spongycastle.crypto.modes;
+
+import org.spongycastle.crypto.BlockCipher;
+import org.spongycastle.crypto.CipherParameters;
+import org.spongycastle.crypto.DataLengthException;
+import org.spongycastle.crypto.params.ParametersWithIV;
+
+/**
+ * Implements the Segmented Integer Counter (SIC) mode on top of a simple
+ * block cipher. This mode is also known as CTR mode.
+ */
+public class SICBlockCipher
+    implements BlockCipher
+{
+    private final BlockCipher     cipher;
+    private final int             blockSize;
+    
+    private byte[]          IV;
+    private byte[]          counter;
+    private byte[]          counterOut;
+
+
+    /**
+     * Basic constructor.
+     *
+     * @param c the block cipher to be used.
+     */
+    public SICBlockCipher(BlockCipher c)
+    {
+        this.cipher = c;
+        this.blockSize = cipher.getBlockSize();
+        this.IV = new byte[blockSize];
+        this.counter = new byte[blockSize];
+        this.counterOut = new byte[blockSize];
+    }
+
+
+    /**
+     * return the underlying block cipher that we are wrapping.
+     *
+     * @return the underlying block cipher that we are wrapping.
+     */
+    public BlockCipher getUnderlyingCipher()
+    {
+        return cipher;
+    }
+
+
+    public void init(
+        boolean             forEncryption, //ignored by this CTR mode
+        CipherParameters    params)
+        throws IllegalArgumentException
+    {
+        if (params instanceof ParametersWithIV)
+        {
+          ParametersWithIV ivParam = (ParametersWithIV)params;
+          byte[]           iv      = ivParam.getIV();
+          System.arraycopy(iv, 0, IV, 0, IV.length);
+
+          reset();
+
+          // if null it's an IV changed only.
+          if (ivParam.getParameters() != null)
+          {
+            cipher.init(true, ivParam.getParameters());
+          }
+        }
+        else
+        {
+            throw new IllegalArgumentException("SIC mode requires ParametersWithIV");
+        }
+    }
+
+    public String getAlgorithmName()
+    {
+        return cipher.getAlgorithmName() + "/SIC";
+    }
+
+    public int getBlockSize()
+    {
+        return cipher.getBlockSize();
+    }
+
+
+    public int processBlock(byte[] in, int inOff, byte[] out, int outOff)
+          throws DataLengthException, IllegalStateException
+    {
+        cipher.processBlock(counter, 0, counterOut, 0);
+
+        //
+        // XOR the counterOut with the plaintext producing the cipher text
+        //
+        for (int i = 0; i < counterOut.length; i++)
+        {
+          out[outOff + i] = (byte)(counterOut[i] ^ in[inOff + i]);
+        }
+
+        // increment counter by 1.
+        for (int i = counter.length - 1; i >= 0 && ++counter[i] == 0; i--)
+        {
+            ; // do nothing - pre-increment and test for 0 in counter does the job.
+        }
+
+        return counter.length;
+    }
+
+
+    public void reset()
+    {
+        System.arraycopy(IV, 0, counter, 0, counter.length);
+        cipher.reset();
+    }
+}