1 files changed, 82 insertions, 0 deletions
diff --git a/Crypto/src/crypto/paddings/X923Padding.cs b/Crypto/src/crypto/paddings/X923Padding.cs
new file mode 100644
index 000000000..cc1b52b3e
--- /dev/null
+++ b/Crypto/src/crypto/paddings/X923Padding.cs
@@ -0,0 +1,82 @@
+using System;
+
+using Org.BouncyCastle.Crypto;
+using Org.BouncyCastle.Security;
+
+namespace Org.BouncyCastle.Crypto.Paddings
+{
+    /**
+    * A padder that adds X9.23 padding to a block - if a SecureRandom is
+    * passed in random padding is assumed, otherwise padding with zeros is used.
+    */
+    public class X923Padding
+		: IBlockCipherPadding
+    {
+        private SecureRandom random;
+
+		/**
+        * Initialise the padder.
+        *
+        * @param random a SecureRandom if one is available.
+        */
+        public void Init(
+			SecureRandom random)
+        {
+            this.random = random;
+        }
+
+		/**
+        * Return the name of the algorithm the cipher implements.
+        *
+        * @return the name of the algorithm the cipher implements.
+        */
+        public string PaddingName
+        {
+            get { return "X9.23"; }
+        }
+
+		/**
+        * add the pad bytes to the passed in block, returning the
+        * number of bytes added.
+        */
+        public int AddPadding(
+            byte[]  input,
+            int     inOff)
+        {
+            byte code = (byte)(input.Length - inOff);
+
+            while (inOff < input.Length - 1)
+            {
+                if (random == null)
+                {
+                    input[inOff] = 0;
+                }
+                else
+                {
+                    input[inOff] = (byte)random.NextInt();
+                }
+                inOff++;
+            }
+
+            input[inOff] = code;
+
+            return code;
+        }
+
+        /**
+        * return the number of pad bytes present in the block.
+        */
+        public int PadCount(
+			byte[] input)
+        {
+            int count = input[input.Length - 1] & 0xff;
+
+            if (count > input.Length)
+            {
+                throw new InvalidCipherTextException("pad block corrupted");
+            }
+
+            return count;
+        }
+    }
+}