After numerous attempts with that code of yours I decided to ditch it - it is simply old, ineffective and unsafe (as noted by Plutonix).
Here's a much more efficient piece of code where I've modified and improved an old class of mine - called Aes256Stream. It is derived from the CryptoStream and will handle the IV automatically for you.
'+---------------------------------------------------------------------------------+'
'| === Aes256Stream === |'
'| |'
'| Created by Vincent "Visual Vincent" Bengtsson |'
'| Website: https://www.mydoomsite.com/ |'
'| |'
'| |'
'| === COPYRIGHT LICENSE === |'
'| |'
'| Copyright (c) 2016-2017, Vincent Bengtsson |'
'| All rights reserved. |'
'| |'
'| Redistribution and use in source and binary forms, with or without |'
'| modification, are permitted provided that the following conditions are met: |'
'| |'
'| 1. Redistributions of source code must retain the above copyright notice, this |'
'| list of conditions and the following disclaimer. |'
'| 2. Redistributions in binary form must reproduce the above copyright notice, |'
'| this list of conditions and the following disclaimer in the documentation |'
'| and/or other materials provided with the distribution. |'
'| |'
'| THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND |'
'| ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |'
'| WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |'
'| DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR |'
'| ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |'
'| (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |'
'| LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |'
'| ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |'
'| (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |'
'| SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |'
'+---------------------------------------------------------------------------------+'
Imports System.IO
Imports System.Security.Cryptography
Imports System.Runtime.InteropServices
Public Class Aes256Stream
Inherits CryptoStream
#Region "Fields"
Private _underlyingStream As Stream
Private AES As RijndaelManaged
Private Transform As ICryptoTransform
#End Region
#Region "Properties"
''' <summary>
''' Gets the block size, in bits, used by the stream's AES algorithm.
''' </summary>
''' <remarks></remarks>
Public ReadOnly Property BlockSize As Integer
Get
Return AES.BlockSize
End Get
End Property
''' <summary>
''' Gets the key size, in bits, used by the stream's AES algorithm.
''' </summary>
''' <remarks></remarks>
Public ReadOnly Property KeySize As Integer
Get
Return AES.KeySize
End Get
End Property
''' <summary>
''' Gets the length in bytes of the underlying stream.
''' </summary>
''' <remarks></remarks>
Public Overrides ReadOnly Property Length As Long
Get
Return _underlyingStream.Length
End Get
End Property
''' <summary>
''' Gets or sets the position within the underlying stream.
''' </summary>
''' <remarks></remarks>
Public Overrides Property Position As Long
Get
If _underlyingStream.CanSeek = False Then Throw New NotSupportedException("The underlying stream doesn't support seeking!")
Return _underlyingStream.Position
End Get
Set(value As Long)
If _underlyingStream.CanSeek = False Then Throw New NotSupportedException("The underlying stream doesn't support seeking!")
_underlyingStream.Position = value
End Set
End Property
''' <summary>
''' Gets the underlying stream.
''' </summary>
''' <remarks></remarks>
Public ReadOnly Property UnderlyingStream As Stream
Get
Return _underlyingStream
End Get
End Property
#End Region
#Region "Constructors"
Private Sub New(ByVal UnderlyingStream As Stream, _
ByVal AES As RijndaelManaged, _
ByVal CryptoTransform As ICryptoTransform, _
ByVal Mode As CryptoStreamMode)
MyBase.New(UnderlyingStream, CryptoTransform, Mode)
Me._underlyingStream = UnderlyingStream
Me.AES = AES
Me.Transform = CryptoTransform
End Sub
#End Region
#Region "Methods"
#Region "Instance"
''' <summary>
''' Sets the length of the underlying stream.
''' </summary>
''' <param name="value">The desired length of underlying stream in bytes.</param>
''' <remarks></remarks>the
Public Overrides Sub SetLength(value As Long)
_underlyingStream.SetLength(value)
End Sub
#End Region
#Region "Shared"
''' <summary>
''' Creates an AES-256 encryption stream.
''' </summary>
''' <param name="UnderlyingStream">The underlying stream to write the encrypted data to.</param>
''' <param name="Key">The encryption key to use when encrypting the data (automatically padded or truncated to KeySize/8 bytes).</param>
''' <remarks></remarks>
Public Shared Function CreateEncryptionStream(ByVal UnderlyingStream As Stream, ByVal Key As Byte()) As Aes256Stream
Dim AES As New RijndaelManaged
AES.KeySize = 256
AES.BlockSize = 128
AES.Key = Aes256Stream.PadOrTruncate(Key, AES.KeySize / 8)
AES.GenerateIV()
AES.Mode = CipherMode.CBC
AES.Padding = PaddingMode.PKCS7
'Write the IV to the underlying stream.
If UnderlyingStream.CanWrite = True Then
Dim LengthIV As Byte() = BitConverter.GetBytes(AES.IV.Length) 'Convert the IV.Length Integer to a byte array.
UnderlyingStream.Write(LengthIV, 0, LengthIV.Length) 'Write the length of the IV.
UnderlyingStream.Write(AES.IV, 0, AES.IV.Length) 'Write the IV.
Else
Throw New IOException("Underlying stream is not writable!")
End If
Return New Aes256Stream(UnderlyingStream, AES, AES.CreateEncryptor(), CryptoStreamMode.Write)
End Function
''' <summary>
''' Creates an AES-256 decryption stream.
''' </summary>
''' <param name="UnderlyingStream">The underlying stream to decrypt the data from.</param>
''' <param name="Key">The encryption key to use when encrypting the data (automatically padded or truncated to KeySize/8 bytes).</param>
''' <remarks></remarks>
Public Shared Function CreateDecryptionStream(ByVal UnderlyingStream As Stream, ByVal Key As Byte()) As Aes256Stream
Dim AES As New RijndaelManaged
AES.KeySize = 256
AES.BlockSize = 128
AES.Key = Aes256Stream.PadOrTruncate(Key, AES.KeySize / 8)
'Read the IV from the underlying stream.
If UnderlyingStream.CanRead = True Then
Dim BytesReadIV As Integer = 0
Dim BufferIV As Byte() = New Byte(Marshal.SizeOf(GetType(Integer)) - 1) {}
Dim LengthIV As Integer
'Read the IV's length.
While BytesReadIV < BufferIV.Length
Dim BytesRead As Integer = UnderlyingStream.Read(BufferIV, BytesReadIV, BufferIV.Length - BytesReadIV)
BytesReadIV += BytesRead
If BytesRead = 0 AndAlso BytesReadIV < BufferIV.Length Then _
Throw New IOException("End of stream reached before IV could be parsed!")
End While
'Convert the bytes to an Integer.
LengthIV = BitConverter.ToInt32(BufferIV, 0)
'Reset the variables.
BytesReadIV = 0
BufferIV = New Byte(LengthIV - 1) {}
'Read the IV.
While BytesReadIV < BufferIV.Length
Dim BytesRead As Integer = UnderlyingStream.Read(BufferIV, BytesReadIV, BufferIV.Length - BytesReadIV)
BytesReadIV += BytesRead
If BytesRead = 0 AndAlso BytesReadIV < BufferIV.Length Then _
Throw New IOException("End of stream reached before IV could be parsed!")
End While
'Set the IV.
AES.IV = BufferIV
Else
Throw New IOException("Underlying stream is not readable!")
End If
AES.Mode = CipherMode.CBC
AES.Padding = PaddingMode.PKCS7
Return New Aes256Stream(UnderlyingStream, AES, AES.CreateDecryptor(), CryptoStreamMode.Read)
End Function
Private Shared Function PadOrTruncate(ByVal Input As Byte(), ByVal PreferredLength As Integer) As Byte()
If Input.Length < PreferredLength Then 'Pad with zeros.
Dim PreviousLength As Integer = Input.Length
Array.Resize(Input, Input.Length + (PreferredLength - Input.Length))
For i = PreviousLength To Input.Length - 1
Input(i) = 0
Next
Return Input
ElseIf Input.Length > PreferredLength Then 'Truncate.
Array.Resize(Input, PreferredLength)
Return Input
End If
Return Input 'Do nothing.
End Function
#End Region
#End Region
#Region "Dispose()"
Protected Overrides Sub Dispose(disposing As Boolean)
MyBase.Dispose(disposing)
If disposing Then
Try
If Transform IsNot Nothing Then
Transform.Dispose()
Transform = Nothing
End If
Catch
End Try
Try
If AES IsNot Nothing Then
AES.Dispose()
AES = Nothing
End If
Catch
End Try
End If
End Sub
#End Region
End Class
The two main things to remember are:
Performing encryption
The simplest example of performing encryption only requires you to create a new Aes256Stream and write to it:
Using AesStream As Aes256Stream = Aes256Stream.CreateEncryptionStream(<output stream>, <encryption key>)
AesStream.Write(<buffer>, <offset>, <length>)
End Using
Notes:
<output stream> is the stream to encrypt the data to (for instance a FileStream).
<encryption key> is the key (as a byte array) to use when encrypting the data.
<buffer>, <offset> and <length> behave just like when you write to a regular stream.
Performing decryption
Likewise the most simple example of performing decryption only requires you to create a new Aes256Stream and read from it:
Using AesStream As Aes256Stream = Aes256Stream.CreateDecryptionStream(<input stream>, <decryption key>)
Dim DecryptedData As Byte() = New Byte(AesStream.Length - 1) {}
AesStream.Read(DecryptedData, 0, DecryptedData.Length)
End Using
Notes:
<input stream> is the stream to decrypt data from (for instance a FileStream).
<decryption key> (same as <encryption key> above).
AesStream.Length is equal to calling <input stream>.Length (same goes for AesStream.Position and <input stream>.Position).
For your use
Here's how you can adapt your code to work with it...
Methods:
''' <summary>
''' Encrypts data to a file.
''' </summary>
''' <param name="File">The file to encrypt data to.</param>
''' <param name="Data">The data to encrypt.</param>
''' <param name="Key">The key to use to perform the encryption.</param>
''' <remarks></remarks>
Public Sub EncryptFile(ByVal File As String, ByVal Data As Byte(), ByVal Key As Byte())
Using OutputStream As New FileStream(File, FileMode.Create, FileAccess.Write, FileShare.None)
Using AesStream As Aes256Stream = Aes256Stream.CreateEncryptionStream(OutputStream, Key)
AesStream.Write(Data, 0, Data.Length)
End Using
End Using
End Sub
''' <summary>
''' Decrypts a file and returns the decrypted data.
''' </summary>
''' <param name="File">The file to decrypt.</param>
''' <param name="Key">The key to use to perform the decryption.</param>
''' <remarks></remarks>
Public Function DecryptFile(ByVal File As String, ByVal Key As Byte()) As Byte()
Using InputStream As New FileStream(File, FileMode.Open, FileAccess.Read, FileShare.Read)
Using DecryptedStream As New MemoryStream
Using AesStream As Aes256Stream = Aes256Stream.CreateDecryptionStream(InputStream, Key)
Dim Buffer As Byte() = New Byte(4096 - 1) {}
While AesStream.Position < AesStream.Length
Dim BytesRead As Integer = AesStream.Read(Buffer, 0, Buffer.Length)
DecryptedStream.Write(Buffer, 0, BytesRead)
End While
Return DecryptedStream.ToArray()
End Using
End Using
End Using
End Function
Usage example:
Dim Key As Byte() = System.Text.Encoding.UTF8.GetBytes("verysecretpassword") 'If you actually use a password here do hash it first!
Dim TextToEncrypt As String = "Hello World! How are you?"
Dim DataToEncrypt As Byte() = System.Text.Encoding.UTF8.GetBytes(TextToEncrypt)
EncryptFile("encrypted.txt", DataToEncrypt, Key)
Dim DecryptedData As Byte() = DecryptFile("encrypted.txt", Key)
Dim DecryptedText As String = System.Text.Encoding.UTF8.GetString(DecryptedData)
Online test
An online testable version of this code can be found here: https://dotnetfiddle.net/PXaJF8
