Made AesStream handle syncing with the counter of the cipher.

ServerMaint/Program.cs

@@ -168,7 +168,7 @@ namespace ServerMaint
                     byte[] keyBytes = Encoding.UTF8.GetBytes(upload.Key);
                     byte[] ivBytes = Encoding.UTF8.GetBytes(upload.IV);
                     FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read);
-                    AESCryptoStream aesStream = new AESCryptoStream(fs, false, keyBytes, ivBytes, "CTR", "NoPadding", 0);
+                    AESCryptoStream aesStream = new AESCryptoStream(fs, false, keyBytes, ivBytes, "CTR", "NoPadding");
 
                     // We have the data, let's scan it
                     ClamScanResult scanResult = clam.SendAndScanFile(aesStream);

Teknik.sln

@@ -26,8 +26,6 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Configuration", "Utilities\
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "TeknikStreaming", "TeknikStreaming\TeknikStreaming.csproj", "{7695CE9A-A0DB-4D73-BC9B-2206481F0254}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Security", "Utilities\Security\Security.csproj", "{2BB2F552-B80F-41F2-937D-5D73F15C6DC4}"
-EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -93,14 +91,6 @@ Global
 		{7695CE9A-A0DB-4D73-BC9B-2206481F0254}.Release|Any CPU.Build.0 = Release|Any CPU
 		{7695CE9A-A0DB-4D73-BC9B-2206481F0254}.Release|x64.ActiveCfg = Release|Any CPU
 		{7695CE9A-A0DB-4D73-BC9B-2206481F0254}.Release|x64.Build.0 = Release|Any CPU
-		{2BB2F552-B80F-41F2-937D-5D73F15C6DC4}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{2BB2F552-B80F-41F2-937D-5D73F15C6DC4}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{2BB2F552-B80F-41F2-937D-5D73F15C6DC4}.Debug|x64.ActiveCfg = Debug|Any CPU
-		{2BB2F552-B80F-41F2-937D-5D73F15C6DC4}.Debug|x64.Build.0 = Debug|Any CPU
-		{2BB2F552-B80F-41F2-937D-5D73F15C6DC4}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{2BB2F552-B80F-41F2-937D-5D73F15C6DC4}.Release|Any CPU.Build.0 = Release|Any CPU
-		{2BB2F552-B80F-41F2-937D-5D73F15C6DC4}.Release|x64.ActiveCfg = Release|Any CPU
-		{2BB2F552-B80F-41F2-937D-5D73F15C6DC4}.Release|x64.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

Teknik/Areas/Upload/Controllers/UploadController.cs

@@ -292,12 +292,9 @@ namespace Teknik.Areas.Upload.Controllers
                                     byte[] keyBytes = Encoding.UTF8.GetBytes(key);
                                     byte[] ivBytes = Encoding.UTF8.GetBytes(iv);
 
-                                    // Calculate the block offset needed for the counter
-                                    int counterOffset = (int)Math.Floor(startByte / 16.0);
-
                                     return new FileGenerateResult(url,
                                                                 contentType,
-                                                                (response) => ResponseHelper.StreamToOutput(response, true, new AESCryptoStream(fs, false, keyBytes, ivBytes, "CTR", "NoPadding", counterOffset), (int)length, Config.UploadConfig.ChunkSize),
+                                                                (response) => ResponseHelper.StreamToOutput(response, true, new AESCryptoStream(fs, false, keyBytes, ivBytes, "CTR", "NoPadding"), (int)length, Config.UploadConfig.ChunkSize),
                                                                 false);
                                 }
                                 else // Otherwise just send it

Teknik/Teknik.csproj

@@ -802,10 +802,6 @@
       <Project>{c492c2c6-d45a-498b-84a2-6d4c8bf9de77}</Project>
       <Name>Piwik</Name>
     </ProjectReference>
-    <ProjectReference Include="..\Utilities\Security\Security.csproj">
-      <Project>{2bb2f552-b80f-41f2-937d-5d73f15c6dc4}</Project>
-      <Name>Security</Name>
-    </ProjectReference>
     <ProjectReference Include="..\Utilities\Utilities\Utilities.csproj">
       <Project>{f45de6fc-3754-4954-a20a-4277362cc6c1}</Project>
       <Name>Utilities</Name>

Utilities/Security/Cryptography/AesCounterMode.cs

@@ -1,137 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Security.Cryptography;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace Teknik.Security.Cryptography
-{
-    public class AesCounterMode : SymmetricAlgorithm
-    {
-        private const int _blockSize = 16;
-        private readonly byte[] _counter;
-        private readonly AesManaged _aes;
-
-        public AesCounterMode(byte[] counter)
-        {
-            if (counter == null) throw new ArgumentNullException("counter");
-            if (counter.Length != _blockSize)
-                throw new ArgumentException(String.Format("Counter size must be same as block size (actual: {0}, expected: {1})",
-                    counter.Length, _blockSize));
-
-            _aes = new AesManaged
-            {
-                Mode = CipherMode.ECB,
-                Padding = PaddingMode.None
-            };
-
-            _counter = counter;
-        }
-
-        public override ICryptoTransform CreateEncryptor(byte[] key, byte[] iv)
-        {
-            return new CounterModeCryptoTransform(_aes, key, iv, _counter);
-        }
-
-        public override ICryptoTransform CreateDecryptor(byte[] key, byte[] iv)
-        {
-            return new CounterModeCryptoTransform(_aes, key, iv, _counter);
-        }
-
-        public override void GenerateKey()
-        {
-            _aes.GenerateKey();
-        }
-
-        public override void GenerateIV()
-        {
-            // IV not needed in Counter Mode
-        }
-    }
-
-    public class CounterModeCryptoTransform : ICryptoTransform
-    {
-        private readonly byte[] _iv;
-        private readonly byte[] _counter;
-        private readonly ICryptoTransform _counterEncryptor;
-        private readonly Queue<byte> _xorMask = new Queue<byte>();
-        private readonly SymmetricAlgorithm _symmetricAlgorithm;
-
-        public CounterModeCryptoTransform(SymmetricAlgorithm symmetricAlgorithm, byte[] key, byte[] iv, byte[] counter)
-        {
-            if (symmetricAlgorithm == null) throw new ArgumentNullException("symmetricAlgorithm");
-            if (key == null) throw new ArgumentNullException("key");
-            if (iv == null) throw new ArgumentNullException("counter");
-            if (iv.Length != symmetricAlgorithm.BlockSize / 8)
-                throw new ArgumentException(String.Format("Counter size must be same as block size (actual: {0}, expected: {1})",
-                    iv.Length, symmetricAlgorithm.BlockSize / 8));
-
-            _symmetricAlgorithm = symmetricAlgorithm;
-            _counter = counter;
-            _iv = iv;
-            
-            _counterEncryptor = symmetricAlgorithm.CreateEncryptor(key, iv);
-        }
-
-        public byte[] TransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
-        {
-            var output = new byte[inputCount];
-            TransformBlock(inputBuffer, inputOffset, inputCount, output, 0);
-            return output;
-        }
-
-        public int TransformBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
-        {
-            for (var i = 0; i < inputCount; i++)
-            {
-                if (NeedMoreXorMaskBytes()) EncryptCounterThenIncrement();
-
-                var mask = _xorMask.Dequeue();
-                outputBuffer[outputOffset + i] = (byte)(mask ^ inputBuffer[inputOffset + i]);
-            }
-
-            return inputCount;
-        }
-
-        private bool NeedMoreXorMaskBytes()
-        {
-            return _xorMask.Count == 0;
-        }
-
-        private void EncryptCounterThenIncrement()
-        {
-            var counterModeBlock = new byte[_symmetricAlgorithm.BlockSize / 8];
-
-            _counterEncryptor.TransformBlock(_counter, 0, _counter.Length, counterModeBlock, 0);
-            IncrementCounter();
-
-            foreach (var b in counterModeBlock)
-            {
-                _xorMask.Enqueue(b);
-            }
-        }
-
-        private void IncrementCounter()
-        {
-            int j = _counter.Length;
-            while (--j >= 0 && ++_counter[j] == 0)
-            {
-            }
-            //for (var i = _counter.Length - 1; i >= 0; i--)
-            //{
-            //    if (++_counter[i] != 0)
-            //        break;
-            //}
-        }
-
-        public int InputBlockSize { get { return _symmetricAlgorithm.BlockSize / 8; } }
-        public int OutputBlockSize { get { return _symmetricAlgorithm.BlockSize / 8; } }
-        public bool CanTransformMultipleBlocks { get { return true; } }
-        public bool CanReuseTransform { get { return false; } }
-
-        public void Dispose()
-        {
-        }
-    }
-}

Utilities/Security/Properties/AssemblyInfo.cs

@@ -1,36 +0,0 @@
-using System.Reflection;
-using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
-
-// General Information about an assembly is controlled through the following 
-// set of attributes. Change these attribute values to modify the information
-// associated with an assembly.
-[assembly: AssemblyTitle("Teknik Security Utilities")]
-[assembly: AssemblyDescription("")]
-[assembly: AssemblyConfiguration("")]
-[assembly: AssemblyCompany("")]
-[assembly: AssemblyProduct("Teknik")]
-[assembly: AssemblyCopyright("Copyright ©  2017")]
-[assembly: AssemblyTrademark("")]
-[assembly: AssemblyCulture("")]
-
-// Setting ComVisible to false makes the types in this assembly not visible 
-// to COM components.  If you need to access a type in this assembly from 
-// COM, set the ComVisible attribute to true on that type.
-[assembly: ComVisible(false)]
-
-// The following GUID is for the ID of the typelib if this project is exposed to COM
-[assembly: Guid("2bb2f552-b80f-41f2-937d-5d73f15c6dc4")]
-
-// Version information for an assembly consists of the following four values:
-//
-//      Major Version
-//      Minor Version 
-//      Build Number
-//      Revision
-//
-// You can specify all the values or you can default the Build and Revision Numbers 
-// by using the '*' as shown below:
-// [assembly: AssemblyVersion("1.0.*")]
-[assembly: AssemblyVersion("1.0.0.0")]
-[assembly: AssemblyFileVersion("1.0.0.0")]

Utilities/Security/Security.csproj

@@ -1,55 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
-  <PropertyGroup>
-    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
-    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
-    <ProjectGuid>{2BB2F552-B80F-41F2-937D-5D73F15C6DC4}</ProjectGuid>
-    <OutputType>Library</OutputType>
-    <AppDesignerFolder>Properties</AppDesignerFolder>
-    <RootNamespace>Teknik.Security</RootNamespace>
-    <AssemblyName>Teknik.Security</AssemblyName>
-    <TargetFrameworkVersion>v4.6.2</TargetFrameworkVersion>
-    <FileAlignment>512</FileAlignment>
-    <TargetFrameworkProfile />
-  </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
-    <DebugSymbols>true</DebugSymbols>
-    <DebugType>full</DebugType>
-    <Optimize>false</Optimize>
-    <OutputPath>bin\Debug\</OutputPath>
-    <DefineConstants>DEBUG;TRACE</DefineConstants>
-    <ErrorReport>prompt</ErrorReport>
-    <WarningLevel>4</WarningLevel>
-  </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
-    <DebugType>pdbonly</DebugType>
-    <Optimize>true</Optimize>
-    <OutputPath>bin\Release\</OutputPath>
-    <DefineConstants>TRACE</DefineConstants>
-    <ErrorReport>prompt</ErrorReport>
-    <WarningLevel>4</WarningLevel>
-  </PropertyGroup>
-  <ItemGroup>
-    <Reference Include="System" />
-    <Reference Include="System.Core" />
-    <Reference Include="System.Xml.Linq" />
-    <Reference Include="System.Data.DataSetExtensions" />
-    <Reference Include="Microsoft.CSharp" />
-    <Reference Include="System.Data" />
-    <Reference Include="System.Net.Http" />
-    <Reference Include="System.Xml" />
-  </ItemGroup>
-  <ItemGroup>
-    <Compile Include="Cryptography\AesCounterMode.cs" />
-    <Compile Include="Properties\AssemblyInfo.cs" />
-  </ItemGroup>
-  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
-  <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
-       Other similar extension points exist, see Microsoft.Common.targets.
-  <Target Name="BeforeBuild">
-  </Target>
-  <Target Name="AfterBuild">
-  </Target>
-  -->
-</Project>

Utilities/Utilities/Cryptography/AesCounterMode.cs

@@ -0,0 +1,187 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Security.Cryptography;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Teknik.Utilities.Cryptography
+{
+    public class AesCounterMode : SymmetricAlgorithm
+    {
+        // Internal Variables
+        private const int _BlockSize = 16;
+        private readonly byte[] _Counter;
+        private readonly AesManaged _Algo;
+
+        public AesCounterMode() : this(new byte[_BlockSize]) { }
+
+        public AesCounterMode(byte[] counter)
+        {
+            if (counter == null) throw new ArgumentNullException("counter");
+            if (counter.Length != _BlockSize)
+                throw new ArgumentException(String.Format("Counter size must be same as block size (actual: {0}, expected: {1})",
+                    counter.Length, _BlockSize));
+
+            // Generate a new instance of the Aes Algorithm in ECB mode with no padding
+            _Algo = new AesManaged
+            {
+                Mode = CipherMode.ECB,
+                Padding = PaddingMode.None
+            };
+
+            // Set the internal variables
+            _Counter = counter;
+        }
+
+        public override ICryptoTransform CreateEncryptor(byte[] key, byte[] iv)
+        {
+            return new CounterModeCryptoTransform(_Algo, key, iv, _Counter);
+        }
+
+        public override ICryptoTransform CreateDecryptor(byte[] key, byte[] iv)
+        {
+            return new CounterModeCryptoTransform(_Algo, key, iv, _Counter);
+        }
+
+        public override void GenerateKey()
+        {
+            _Algo.GenerateKey();
+        }
+
+        public override void GenerateIV()
+        {
+            _Algo.GenerateIV();
+        }
+    }
+
+    public class CounterModeCryptoTransform : ICryptoTransform
+    {
+        private readonly byte[] _IV;
+        private readonly byte[] _Counter;
+        private readonly ICryptoTransform _CounterEncryptor;
+        private readonly SymmetricAlgorithm _SymmetricAlgorithm;
+
+        // Stateful Fields
+        private byte[] _EncryptedCounter;
+
+        private int _Iterations;
+        public int Iterations
+        {
+            get
+            {
+                return _Iterations;
+            }
+        }
+
+        private int _CounterPosition;
+        public int CounterPosition
+        {
+            get
+            {
+                return _CounterPosition;
+            }
+            set
+            {
+                if (value > 0 && value < _EncryptedCounter.Length)
+                {
+                    _CounterPosition = value;
+                }
+            }
+        }
+
+        public CounterModeCryptoTransform(SymmetricAlgorithm symmetricAlgorithm, byte[] key, byte[] iv, byte[] counter)
+        {
+            if (symmetricAlgorithm == null) throw new ArgumentNullException("symmetricAlgorithm");
+            if (key == null) throw new ArgumentNullException("key");
+            if (iv == null) throw new ArgumentNullException("iv");
+            if (counter == null) throw new ArgumentNullException("counter");
+
+            // Check lengths
+            if (counter.Length != symmetricAlgorithm.BlockSize / 8)
+                throw new ArgumentException(String.Format("Counter size must be same as block size (actual: {0}, expected: {1})",
+                    counter.Length, symmetricAlgorithm.BlockSize / 8));
+
+            _SymmetricAlgorithm = symmetricAlgorithm;
+            _IV = iv;
+            _Counter = counter;
+            
+            _CounterEncryptor = symmetricAlgorithm.CreateEncryptor(key, iv);
+
+            // Initialize State
+            _CounterPosition = 0;
+            _Iterations = 0;
+
+            // Encrypt the counter
+            EncryptCounter();
+        }
+
+        public byte[] TransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
+        {
+            var output = new byte[inputCount];
+            TransformBlock(inputBuffer, inputOffset, inputCount, output, 0);
+            return output;
+        }
+
+        public int TransformBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
+        {
+            for (var i = 0; i < inputCount; i++)
+            {
+                // Encrypt the counter if we have reached the end, or 
+                if (_CounterPosition >= _EncryptedCounter.Length)
+                {
+                    // Encrypt the counter
+                    EncryptCounter();
+
+                    //Reset current counter position
+                    _CounterPosition = 0;
+
+                    // Increment the counter for the next run
+                    IncrementCounter();
+                }
+                
+                // XOR the encrypted counter with the input plain text
+                outputBuffer[outputOffset + i] = (byte)(_EncryptedCounter[_CounterPosition] ^ inputBuffer[inputOffset + i]);
+
+                // Move the counter position
+                _CounterPosition++;
+            }
+
+            return inputCount;
+        }
+
+        public void EncryptCounter()
+        {
+            // Clear the encrypted counter
+            _EncryptedCounter = new byte[_SymmetricAlgorithm.BlockSize / 8];
+
+            // Encrypt the current counter to the encrypted counter
+            _CounterEncryptor.TransformBlock(_Counter, 0, _Counter.Length, _EncryptedCounter, 0);
+        }
+
+        public void ResetCounter()
+        {
+            Array.Clear(_Counter, 0, _Counter.Length);
+            Array.Copy(_IV, 0, _Counter, 0, _IV.Length);
+            _Iterations = 0;
+        }
+
+        public void IncrementCounter()
+        {
+            int j = _Counter.Length;
+            while (--j >= 0 && ++_Counter[j] == 0)
+            {
+            }
+            _Iterations++;
+        }
+
+        public int InputBlockSize { get { return _SymmetricAlgorithm.BlockSize / 8; } }
+        public int OutputBlockSize { get { return _SymmetricAlgorithm.BlockSize / 8; } }
+        public bool CanTransformMultipleBlocks { get { return true; } }
+        public bool CanReuseTransform { get { return false; } }
+
+        public void Dispose()
+        {
+        }
+    }
+}

Utilities/Utilities/StreamHelper.cs

@@ -5,105 +5,59 @@ using System.Linq;
 using System.Security.Cryptography;
 using System.Text;
 using System.Threading.Tasks;
-using Teknik.Security.Cryptography;
+using Teknik.Utilities.Cryptography;
 
 namespace Teknik.Utilities
 {
     public class AESCryptoStream : Stream
     {
         private Stream _Inner;
-        //private IBufferedCipher _Cipher;
+        private CounterModeCryptoTransform _Cipher;
-        private ICryptoTransform _Cipher;
 
-        public AESCryptoStream(Stream stream, bool encrypt, byte[] key, byte[] iv, string mode, string padding, int initCounter)
+        public AESCryptoStream(Stream stream, bool encrypt, byte[] key, byte[] iv, string mode, string padding)
         {
             _Inner = stream;
 
-            // Create initial counter value from IV
-            byte[] counter = new byte[iv.Length];
-            iv.CopyTo(counter, 0);
-
-            // Increment the counter depending on the init counter
-            for (int i = 0; i < initCounter; i++)
-            {
-                int j = counter.Length;
-                while (--j >= 0 && ++counter[j] == 0) { }
-            }
-
             // Create the Aes Cipher
-            AesCounterMode aes = new AesCounterMode(counter);
+            AesCounterMode aes = new AesCounterMode(iv);
             if (encrypt)
             {
-                _Cipher = aes.CreateEncryptor(key, iv); // Encrypt
+                _Cipher = (CounterModeCryptoTransform)aes.CreateEncryptor(key, iv); // Encrypt
             }
             else
             {
-                _Cipher = aes.CreateDecryptor(key, iv); // Decrypt
+                _Cipher = (CounterModeCryptoTransform)aes.CreateDecryptor(key, iv); // Decrypt
             }
+
+            // Sync the counter
+            SyncCounter();
         }
 
         public override int Read(byte[] buffer, int offset, int count)
         {
             if (_Inner != null && CanRead)
             {
-                int bytesRead = 0;
+                byte[] readBuf = new byte[count];
-                int totalBytesRead = 0;
+                int processed = 0;
-                int bytesProcessed = 0;
-                long startPosition = _Inner.Position;
-                int blockSize = _Cipher.InputBlockSize;
-                long byteOffset = (startPosition % blockSize);
-                int initialOffset = (int)byteOffset;
-                int blockOffset = (byteOffset == 0) ? 0 : 1;
-                int blocksToProcess = (int)Math.Ceiling(count / (double)blockSize) + blockOffset;
 
-                // Determine if we are at the start of a block, or not
+                // Read the data from the stream
-                if (byteOffset != 0)
+                int bytesRead = _Inner.Read(readBuf, 0, count);
+                if (bytesRead > 0)
                 {
-                    // We are not a multiple of the block size, so let's backup to get the current block
+                    // Process the 
-                    _Inner.Seek(startPosition - byteOffset, SeekOrigin.Begin);
+                    processed = _Cipher.TransformBlock(readBuf, 0, bytesRead, buffer, 0);
                 }
 
-                // Initialize buffers
+                // Do we have more?
-                byte[] readBuf = new byte[blockSize];
+                if (processed < bytesRead)
-                byte[] outBuf = new byte[blockSize];
-
-                // Iterate through each block of the ammount we want to read
-                for (int i = 0; i < blocksToProcess; i++)
-                {
-                    // Read the next block of data
-                    totalBytesRead += bytesRead = _Inner.Read(readBuf, 0, blockSize);
-                    if (bytesRead > 0)
-                    {
-                        // process the cipher for the read block and add it to the output
-                        int processed = _Cipher.TransformBlock(readBuf, 0, bytesRead, outBuf, 0);
-
-                        // copy the values to the output
-                        outBuf.Skip(initialOffset).ToArray().CopyTo(buffer, bytesProcessed + offset);
-
-                        // Reset initial offset and calibrate
-                        bytesProcessed += processed - initialOffset;
-
-                        // Reset initial offset
-                        initialOffset = 0;
-                    }
-
-                    // Clear the read buffer
-                    Array.Clear(readBuf, 0, blockSize);
-                }
-
-                // Adjust bytes read by the block offset
-                totalBytesRead -= (int)byteOffset;
-                bytesProcessed -= (int)byteOffset;
-
-                if (bytesProcessed < count)
                 {
                     // Finalize the cipher
-                    byte[] finalBuf = _Cipher.TransformFinalBlock(readBuf, bytesProcessed, bytesRead);
+                    byte[] finalBuf = _Cipher.TransformFinalBlock(readBuf, processed, bytesRead);
-                    finalBuf.Take(count - bytesProcessed).ToArray().CopyTo(buffer, bytesProcessed);
+                    finalBuf.CopyTo(buffer, processed);
-                    bytesProcessed += count - bytesProcessed;
+                    processed += finalBuf.Length;
                 }
 
-                return bytesProcessed;
+                return processed;
             }
             return -1;
         }
@@ -187,6 +141,9 @@ namespace Teknik.Utilities
                 if (_Inner != null)
                 {
                     _Inner.Position = value;
+
+                    // Sync the counter
+                    SyncCounter();
                 }
             }
         }
@@ -203,7 +160,12 @@ namespace Teknik.Utilities
         {
             if (_Inner != null)
             {
-                return _Inner.Seek(offset, origin);
+                long newPos = _Inner.Seek(offset, origin);
+
+                // Sync the counter
+                SyncCounter();
+
+                return newPos;
             }
             return -1;
         }
@@ -215,5 +177,37 @@ namespace Teknik.Utilities
                 _Inner.SetLength(value);
             }
         }
+
+        private void SyncCounter()
+        {
+            if (_Cipher != null)
+            {
+                // Calculate the counter iterations and position needed
+                int iterations = (int)Math.Floor(_Inner.Position / (decimal)_Cipher.InputBlockSize);
+                int counterPos = (int)(_Inner.Position % _Cipher.InputBlockSize);
+
+                // Are we out of sync with the cipher?
+                if (_Cipher.Iterations != iterations || _Cipher.CounterPosition != counterPos)
+                {
+                    // Reset the current counter
+                    _Cipher.ResetCounter();
+
+                    // Iterate the counter to the current position
+                    for (int i = 0; i < iterations; i++)
+                    {
+                        _Cipher.IncrementCounter();
+                    }
+
+                    // Encrypt the counter
+                    _Cipher.EncryptCounter();
+
+                    // Set the current position of the counter
+                    _Cipher.CounterPosition = counterPos;
+
+                    // Increment the counter for the next time
+                    _Cipher.IncrementCounter();
+                }
+            }
+        }
     }
 }

Utilities/Utilities/Utilities.csproj

@@ -106,6 +106,7 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="AccountType.cs" />
+    <Compile Include="Cryptography\AesCounterMode.cs" />
     <Compile Include="CurrencyHelper.cs" />
     <Compile Include="CurrencyType.cs" />
     <Compile Include="EntityExtensions.cs" />
@@ -139,12 +140,6 @@
     <None Include="app.config" />
     <None Include="packages.config" />
   </ItemGroup>
-  <ItemGroup>
-    <ProjectReference Include="..\Security\Security.csproj">
-      <Project>{2bb2f552-b80f-41f2-937d-5d73f15c6dc4}</Project>
-      <Name>Security</Name>
-    </ProjectReference>
-  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <Import Project="..\..\packages\GitVersionTask.3.6.5\build\dotnet\GitVersionTask.targets" Condition="Exists('..\..\packages\GitVersionTask.3.6.5\build\dotnet\GitVersionTask.targets')" />
   <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">