[RESOLVED] "Padding is invalid and cannot be removed."

[tassa]

Hello,

I'm using this class to encrypt/decrypt a file:

Imports System.Security.Cryptography
Imports System.Text
Imports System.IO
 
Public Class EncryptFile
 
    Private Shared Buffer(4096) As Byte
    Private Shared _Rijndael As New RijndaelManaged
    Private Shared _Hash As New SHA256Managed
    Private Shared _Encoding As New UTF8Encoding
    Private Shared IV As Byte() = {12, 4, 58, 74, 52, 33, 69, 87, 47, 8, 23, 69, 85, 47, 85, 21}
    Private Shared cStream As CryptoStream
    Enum Action
        Encrypt = 0
        Decrypt = 1
    End Enum
 
    Public Shared Function EncryptDecrypt(ByVal source As String, ByVal destination As String, _
                                          ByVal key As String, ByVal actions As Action) As Integer
        Dim sourceStream As New FileStream(source, FileMode.Open, FileAccess.Read)
        Dim destinationStream As New FileStream(destination, FileMode.OpenOrCreate, FileAccess.Write)
        Dim BytesProcessed As Long = 0
        Dim SourceLength As Long = sourceStream.Length
        Dim CurrentByteProcess As Integer = 0
        Dim PercentDone As Integer = 0
        Dim _key As Byte() = _Hash.ComputeHash(_Encoding.GetBytes(key))
 
        Select Case direction
            Case EncryptFile.Action.Encrypt
                cStream = New CryptoStream(destinationStream, _
                                           _Rijndael.CreateEncryptor(_key, IV), _
                                        CryptoStreamMode.Write)
            Case EncryptFile.Action.Decrypt
                cStream = New CryptoStream(destinationStream, _
                                          _Rijndael.CreateDecryptor(_key, IV), _
                                          CryptoStreamMode.Write)
        End Select
 
        While BytesProcessed < SourceLength
            CurrentByteProcess = sourceStream.Read(Buffer, 0, 4096)
            cStream.Write(Buffer, 0, 4096)
            BytesProcessed += CLng(CurrentByteProcess)
            PercentDone = CInt((BytesProcessed / SourceLength) * 100)
        End While
 
        cStream.Close()
        destinationStream.Close()
        sourceStream.Close()
 
        Return PercentDone
    End Function
End Class

When I encrypt a file it gives me no error, but when I decrypt a file it gives me this error:

Padding is invalid and cannot be removed.

In this line:

cStream.Close()

I don't understand why, because I'm using the same IV and the same key, I've even checked the generated hash, and to me, it seems the same.

I read that this error is generated if you don't use the same IV, but in this case it's impossible, since I've declared it before even using it!

I'm sorry, it's just driving me crazy, I don't know what's wrong.

Thanks in advance!