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diff --git a/src/org/bouncycastle/crypto/digests/GeneralDigest.java b/src/org/bouncycastle/crypto/digests/GeneralDigest.java
new file mode 100644
index 0000000..2d319b7
--- /dev/null
+++ b/src/org/bouncycastle/crypto/digests/GeneralDigest.java
@@ -0,0 +1,128 @@
+package org.bouncycastle.crypto.digests;
+
+import org.bouncycastle.crypto.Digest;
+
+/**
+ * base implementation of MD4 family style digest as outlined in
+ * "Handbook of Applied Cryptography", pages 344 - 347.
+ */
+public abstract class GeneralDigest
+    implements Digest
+{
+    private byte[]  xBuf;
+    private int     xBufOff;
+
+    private long    byteCount;
+
+	/**
+	 * Standard constructor
+	 */
+	protected GeneralDigest()
+	{
+		xBuf = new byte[4];
+		xBufOff = 0;
+	}
+
+	/**
+	 * Copy constructor.  We are using copy constructors in place
+	 * of the Object.clone() interface as this interface is not
+	 * supported by J2ME.
+	 */
+	protected GeneralDigest(GeneralDigest t)
+	{
+        xBuf = new byte[t.xBuf.length];
+		System.arraycopy(t.xBuf, 0, xBuf, 0, t.xBuf.length);
+
+		xBufOff = t.xBufOff;
+		byteCount = t.byteCount;
+	}
+
+    public void update(
+        byte in)
+    {
+        xBuf[xBufOff++] = in;
+
+        if (xBufOff == xBuf.length)
+        {
+            processWord(xBuf, 0);
+            xBufOff = 0;
+        }
+
+        byteCount++;
+    }
+
+    public void update(
+        byte[]  in,
+        int     inOff,
+        int     len)
+    {
+        //
+        // fill the current word
+        //
+        while ((xBufOff != 0) && (len > 0))
+        {
+            update(in[inOff]);
+
+            inOff++;
+            len--;
+        }
+
+        //
+        // process whole words.
+        //
+        while (len > xBuf.length)
+        {
+            processWord(in, inOff);
+
+            inOff += xBuf.length;
+            len -= xBuf.length;
+            byteCount += xBuf.length;
+        }
+
+        //
+        // load in the remainder.
+        //
+        while (len > 0)
+        {
+            update(in[inOff]);
+
+            inOff++;
+            len--;
+        }
+    }
+
+    public void finish()
+    {
+        long    bitLength = (byteCount << 3);
+
+        //
+        // add the pad bytes.
+        //
+        update((byte)128);
+
+        while (xBufOff != 0)
+        {
+            update((byte)0);
+        }
+
+        processLength(bitLength);
+
+        processBlock();
+    }
+
+    public void reset()
+    {
+        byteCount = 0;
+
+        xBufOff = 0;
+		for ( int i = 0; i < xBuf.length; i++ ) {
+			xBuf[i] = 0;
+		}
+    }
+
+    protected abstract void processWord(byte[] in, int inOff);
+
+    protected abstract void processLength(long bitLength);
+
+    protected abstract void processBlock();
+}