Initial Commit

iTechSharp/srcbc/crypto/paddings/TbcPadding.cs

@@ -0,0 +1,79 @@
+using System;
+using Org.BouncyCastle.Crypto;
+using Org.BouncyCastle.Security;
+
+namespace Org.BouncyCastle.Crypto.Paddings
+{
+
+    /// <summary> A padder that adds Trailing-Bit-Compliment padding to a block.
+    /// <p>
+    /// This padding pads the block out compliment of the last bit
+    /// of the plain text.
+    /// </p>
+    /// </summary>
+    public class TbcPadding
+		: IBlockCipherPadding
+    {
+        /// <summary> Return the name of the algorithm the cipher implements.</summary>
+        /// <returns> the name of the algorithm the cipher implements.
+        /// </returns>
+        public string PaddingName
+        {
+            get { return "TBC"; }
+        }
+
+		/// <summary> Initialise the padder.</summary>
+        /// <param name="random">- a SecureRandom if available.
+        /// </param>
+        public virtual void Init(SecureRandom random)
+        {
+            // nothing to do.
+        }
+
+        /// <summary> 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>
+        /// </summary>
+        public virtual int AddPadding(byte[] input, int inOff)
+        {
+            int count = input.Length - inOff;
+            byte code;
+
+            if (inOff > 0)
+            {
+                code = (byte)((input[inOff - 1] & 0x01) == 0?0xff:0x00);
+            }
+            else
+            {
+                code = (byte)((input[input.Length - 1] & 0x01) == 0?0xff:0x00);
+            }
+
+            while (inOff < input.Length)
+            {
+                input[inOff] = code;
+                inOff++;
+            }
+
+            return count;
+        }
+
+        /// <summary> return the number of pad bytes present in the block.</summary>
+        public virtual int PadCount(byte[] input)
+        {
+            byte code = input[input.Length - 1];
+
+            int index = input.Length - 1;
+            while (index > 0 && input[index - 1] == code)
+            {
+                index--;
+            }
+
+            return input.Length - index;
+        }
+    }
+}