1 files changed, 80 insertions, 0 deletions
diff --git a/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/paddings/X923Padding.java b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/paddings/X923Padding.java
new file mode 100644
index 000000000..e5b8992f1
--- /dev/null
+++ b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/paddings/X923Padding.java
@@ -0,0 +1,80 @@
+package org.spongycastle.crypto.paddings;
+
+import java.security.SecureRandom;
+
+import org.spongycastle.crypto.InvalidCipherTextException;
+
+/**
+ * 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
+    implements BlockCipherPadding
+{
+    SecureRandom    random = null;
+
+    /**
+     * Initialise the padder.
+     *
+     * @param random a SecureRandom if one is available.
+     */
+    public void init(SecureRandom random)
+        throws IllegalArgumentException
+    {
+        this.random = random;
+    }
+
+    /**
+     * Return the name of the algorithm the padder implements.
+     *
+     * @return the name of the algorithm the padder implements.
+     */
+    public String getPaddingName()
+    {
+        return "X9.23";
+    }
+
+    /**
+     * add the pad bytes to the passed in block, returning the
+     * number of bytes added.
+     */
+    public int addPadding(
+        byte[]  in,
+        int     inOff)
+    {
+        byte code = (byte)(in.length - inOff);
+
+        while (inOff < in.length - 1)
+        {
+            if (random == null)
+            {
+                in[inOff] = 0;
+            }
+            else
+            {
+                in[inOff] = (byte)random.nextInt();
+            }
+            inOff++;
+        }
+
+        in[inOff] = code;
+
+        return code;
+    }
+
+    /**
+     * return the number of pad bytes present in the block.
+     */
+    public int padCount(byte[] in)
+        throws InvalidCipherTextException
+    {
+        int count = in[in.length - 1] & 0xff;
+
+        if (count > in.length)
+        {
+            throw new InvalidCipherTextException("pad block corrupted");
+        }
+
+        return count;
+    }
+}