finished basic HMAC class

Author: john-h-k

src/Backend/MessageAuthenticator.cs

@@ -1,25 +1,64 @@
 using System;
 using System.IO;
+using System.Linq;
 using System.Security.Cryptography;
 
 namespace Encryption_App
 {
     class MessageAuthenticator
     {
-        public void VerifyHMACFile(byte[] data, byte[] key)
+        public byte[] CreateHMAC(byte[] data, byte[] key)
         {
             byte[] hashKey;
 
             using (var hmac = new HMACSHA384(key))
             {
-                if (key.Length > hmac.InputBlockSize)
-                {
-                    hashKey = hmac.ComputeHash(data);
-                }
+                hashKey = hmac.ComputeHash(data);
             }
+
+            return hashKey;
+        }
+
+        public byte[] CreateHMAC(byte[] data, byte[] key, Type TypeOfHash)
+        {
+            HMAC hmac;
+            if (TypeOfHash.IsSubclassOf(typeof(HMAC)))
+            {
+                hmac = (HMAC)Activator.CreateInstance(TypeOfHash);
+            }
+            else
+            {
+                throw new ArgumentException("TypeOfHash is not a derivative of \"System.Security.Cryptorgaphy.HMAC\"");
+            }
+
+            byte[] hashKey;
+
+            using (hmac)
+            {
+                hashKey = hmac.ComputeHash(data);
+            }
+
+            return hashKey;
+        }
+
+        public bool VerifyHMAC(byte[] data, byte[] key, byte[] hash)
+        {
+            byte[] hashKey;
+
+            using (var hmac = new HMACSHA384(key))
+            {
+                hashKey = hmac.ComputeHash(data);
+            }
+
+            if (data.SequenceEqual(hash))
+            {
+                return true;
+            }
+
+            return false;
         }
 
-        public void VerifyHMACFile(byte[] data, byte[] key, Type TypeOfHash)
+        public bool VerifyHMAC(byte[] data, byte[] key, byte[] hash, Type TypeOfHash)
         {
             HMAC hmac;
             if (TypeOfHash.IsSubclassOf(typeof(HMAC)))
@@ -30,6 +69,20 @@ public void VerifyHMACFile(byte[] data, byte[] key, Type TypeOfHash)
             {
                 throw new ArgumentException("TypeOfHash is not a derivative of \"System.Security.Cryptorgaphy.HMAC\"");
             }
+
+            byte[] hashKey;
+
+            using (hmac)
+            {
+                hashKey = hmac.ComputeHash(data);
+            }
+
+            if (data.SequenceEqual(hash))
+            {
+                return true;
+            }
+
+            return false;
         }
     }
 }