1 files changed, 89 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/crypto/paddings/TBCPadding.java b/core/src/main/java/org/spongycastle/crypto/paddings/TBCPadding.java
new file mode 100644
index 00000000..4b8190df
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/crypto/paddings/TBCPadding.java
@@ -0,0 +1,89 @@
+package org.spongycastle.crypto.paddings;
+
+import java.security.SecureRandom;
+
+import org.spongycastle.crypto.InvalidCipherTextException;
+
+/**
+ * A padder that adds Trailing-Bit-Compliment padding to a block.
+ * <p>
+ * This padding pads the block out with the compliment of the last bit
+ * of the plain text.
+ * </p>
+ */
+public class TBCPadding
+    implements BlockCipherPadding
+{
+    /**
+     * Initialise the padder.
+     *
+     * @param random - a SecureRandom if available.
+     */
+    public void init(SecureRandom random)
+        throws IllegalArgumentException
+    {
+        // nothing to do.
+    }
+
+    /**
+     * Return the name of the algorithm the padder implements.
+     *
+     * @return the name of the algorithm the padder implements.
+     */
+    public String getPaddingName()
+    {
+        return "TBC";
+    }
+
+    /**
+     * add the pad bytes to the passed in block, returning the
+     * number of bytes added.
+     * <p>
+     * Note: this assumes that the last block of plain text is always 
+     * passed to it inside in. i.e. if inOff is zero, indicating the
+     * entire block is to be overwritten with padding the value of in
+     * should be the same as the last block of plain text.
+     * </p>
+     */
+    public int addPadding(
+        byte[]  in,
+        int     inOff)
+    {
+        int     count = in.length - inOff;
+        byte    code;
+        
+        if (inOff > 0)
+        {
+            code = (byte)((in[inOff - 1] & 0x01) == 0 ? 0xff : 0x00);
+        }
+        else
+        {
+            code = (byte)((in[in.length - 1] & 0x01) == 0 ? 0xff : 0x00);
+        }
+            
+        while (inOff < in.length)
+        {
+            in[inOff] = code;
+            inOff++;
+        }
+
+        return count;
+    }
+
+    /**
+     * return the number of pad bytes present in the block.
+     */
+    public int padCount(byte[] in)
+        throws InvalidCipherTextException
+    {
+        byte code = in[in.length - 1];
+
+        int index = in.length - 1;
+        while (index > 0 && in[index - 1] == code)
+        {
+            index--;
+        }
+
+        return in.length - index;
+    }
+}