diff --git a/Crypto/src/crypto/io/MacStream.cs b/Crypto/src/crypto/io/MacStream.cs
new file mode 100644
index 000000000..419eafb77
--- /dev/null
+++ b/Crypto/src/crypto/io/MacStream.cs
@@ -0,0 +1,139 @@
+using System;
+using System.IO;
+
+namespace Org.BouncyCastle.Crypto.IO
+{
+ public class MacStream
+ : Stream
+ {
+ protected readonly Stream stream;
+ protected readonly IMac inMac;
+ protected readonly IMac outMac;
+
+ public MacStream(
+ Stream stream,
+ IMac readMac,
+ IMac writeMac)
+ {
+ this.stream = stream;
+ this.inMac = readMac;
+ this.outMac = writeMac;
+ }
+
+ public virtual IMac ReadMac()
+ {
+ return inMac;
+ }
+
+ public virtual IMac WriteMac()
+ {
+ return outMac;
+ }
+
+ public override int Read(
+ byte[] buffer,
+ int offset,
+ int count)
+ {
+ int n = stream.Read(buffer, offset, count);
+ if (inMac != null)
+ {
+ if (n > 0)
+ {
+ inMac.BlockUpdate(buffer, offset, n);
+ }
+ }
+ return n;
+ }
+
+ public override int ReadByte()
+ {
+ int b = stream.ReadByte();
+ if (inMac != null)
+ {
+ if (b >= 0)
+ {
+ inMac.Update((byte)b);
+ }
+ }
+ return b;
+ }
+
+ public override void Write(
+ byte[] buffer,
+ int offset,
+ int count)
+ {
+ if (outMac != null)
+ {
+ if (count > 0)
+ {
+ outMac.BlockUpdate(buffer, offset, count);
+ }
+ }
+ stream.Write(buffer, offset, count);
+ }
+
+ public override void WriteByte(byte b)
+ {
+ if (outMac != null)
+ {
+ outMac.Update(b);
+ }
+ stream.WriteByte(b);
+ }
+
+ public override bool CanRead
+ {
+ get { return stream.CanRead; }
+ }
+
+ public override bool CanWrite
+ {
+ get { return stream.CanWrite; }
+ }
+
+ public override bool CanSeek
+ {
+ get { return stream.CanSeek; }
+ }
+
+ public override long Length
+ {
+ get { return stream.Length; }
+ }
+
+ public override long Position
+ {
+ get { return stream.Position; }
+ set { stream.Position = value; }
+ }
+
+ protected override void Dispose(bool disposing)
+ {
+ if (disposing)
+ {
+ stream.Dispose();
+ }
+ }
+
+ public override void Flush()
+ {
+ stream.Flush();
+ }
+
+ public override long Seek(
+ long offset,
+ SeekOrigin origin)
+ {
+ return stream.Seek(offset,origin);
+ }
+
+ public override void SetLength(
+ long length)
+ {
+ stream.SetLength(length);
+ }
+ }
+}
+
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