diff --git a/Crypto/src/crypto/tls/TlsMac.cs b/Crypto/src/crypto/tls/TlsMac.cs
new file mode 100644
index 000000000..0e58b89dc
--- /dev/null
+++ b/Crypto/src/crypto/tls/TlsMac.cs
@@ -0,0 +1,106 @@
+using System;
+using System.IO;
+
+using Org.BouncyCastle.Crypto.Digests;
+using Org.BouncyCastle.Crypto.Macs;
+using Org.BouncyCastle.Crypto.Parameters;
+using Org.BouncyCastle.Security;
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Crypto.Tls
+{
+ /// <remarks>
+ /// A generic TLS MAC implementation, which can be used with any kind of
+ /// IDigest to act as an HMAC.
+ /// </remarks>
+ public class TlsMac
+ {
+ protected long seqNo;
+ protected byte[] secret;
+ protected HMac mac;
+
+ /**
+ * Generate a new instance of an TlsMac.
+ *
+ * @param digest The digest to use.
+ * @param key_block A byte-array where the key for this mac is located.
+ * @param offset The number of bytes to skip, before the key starts in the buffer.
+ * @param len The length of the key.
+ */
+ public TlsMac(
+ IDigest digest,
+ byte[] key_block,
+ int offset,
+ int len)
+ {
+ this.seqNo = 0;
+
+ KeyParameter param = new KeyParameter(key_block, offset, len);
+
+ this.secret = Arrays.Clone(param.GetKey());
+
+ this.mac = new HMac(digest);
+ this.mac.Init(param);
+ }
+
+ /**
+ * @return the MAC write secret
+ */
+ public virtual byte[] GetMacSecret()
+ {
+ return this.secret;
+ }
+
+ /**
+ * @return the current write sequence number
+ */
+ public virtual long SequenceNumber
+ {
+ get { return this.seqNo; }
+ }
+
+ /**
+ * Increment the current write sequence number
+ */
+ public virtual void IncSequenceNumber()
+ {
+ this.seqNo++;
+ }
+
+ /**
+ * @return The Keysize of the mac.
+ */
+ public virtual int Size
+ {
+ get { return mac.GetMacSize(); }
+ }
+
+ /**
+ * Calculate the mac for some given data.
+ * <p/>
+ * TlsMac will keep track of the sequence number internally.
+ *
+ * @param type The message type of the message.
+ * @param message A byte-buffer containing the message.
+ * @param offset The number of bytes to skip, before the message starts.
+ * @param len The length of the message.
+ * @return A new byte-buffer containing the mac value.
+ */
+ public virtual byte[] CalculateMac(
+ ContentType type,
+ byte[] message,
+ int offset,
+ int len)
+ {
+ byte[] macHeader = new byte[13];
+ TlsUtilities.WriteUint64(seqNo++, macHeader, 0);
+ TlsUtilities.WriteUint8((byte)type, macHeader, 8);
+ TlsUtilities.WriteVersion(macHeader, 9);
+ TlsUtilities.WriteUint16(len, macHeader, 11);
+
+ mac.BlockUpdate(macHeader, 0, macHeader.Length);
+ mac.BlockUpdate(message, offset, len);
+ return MacUtilities.DoFinal(mac);
+ }
+ }
+}
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