VB.NET - Symmetric Encryption/Decryption (Not using files)

[SnOrfus]

Half of the code online that I could find was useless. All of the msdn examples read in from a file, and then output it all to a file... and all of the 'tutorials' that I've found online have serious issues that are always left unanswered. It should also be noted that this code was made in Beta 2.0 of the .NET framework, but it works in 1.1.

First of all, this is the interface that the encryption classes will follow. This allows us to easily create an abstract factory where we can add new encryption algorithms, and create them without changing much of the existing code.

Public Interface ICrypto
    Function BlockSize() As Integer
    Function KeySize() As Integer

    Function Encrypt(ByVal data As String) As String
    Function Decrypt(ByVal data As String) As String
End Interface

The abstract factory that will create whatever cryptographic object we have available. Just pass in the name of the encryption that you want to use, and it gives you back the object. (More on this in a second)

Public Class CryptoFactory
    Public Function MakeCryptographer(ByVal type As String) As ICrypto
        Select Case type.ToLower
            Case "des"
                Return New DES()
            Case "tripledes"
                Return New TripleDES()
            Case "rijndael"
                Return New Rijndael()
            Case Else
                Return New TripleDES()
        End Select
    End Function
End Class

Here are the goods. This will perform the encryption and decryption. One thing that I do want to mention here is that there is no way to adjust the key or iv at runtime using my code, you will have to modify it yourself. They must be adjusted at design time and cannot be changed once the program is implemented. This is due to the environment that I am going to be implementing the software in. The key and block(iv) size are given in bits... This was because different algorithms have different key/iv sizes. Remember this if you decide to create more encryption/decryption algorithms (as I ran into problems, easy to fix, but problems none-the-less).

Note 1: If you don't want to use the factory at all, you can just copy/paste the encrypt/decrypt functions.
Note 2: In the interest of space, the other algorithms aren't placed here, but they are practically the exact same as this, but using the different .NET objects.

Imports System.IO
Imports System.Text
Imports System.Security.Cryptography

Public Class Rijndael
    Implements ICrypto

    ' The key and initialization vector : change them for your application
    Private _key() As Byte = {132, 42, 53, 124, 75, 56, 87, 38, 9, 10, 161, 132, 183, _
91, 105, 16, 117, 218, 149, 230, 221, 212, 235, 64}
    Private _iv() As Byte = {83, 71, 26, 58, 54, 35, 22, 11, 83, 71, 26, 58, 54, 35, 22, 11}

    ' returns the default size, in bits of the iv
    Public Function BlockSize() As Integer Implements ICrypto.BlockSize
        Dim aes As New RijndaelManaged()

        Return aes.BlockSize
    End Function

    ' returns the default size, in bits of the key
    Public Function KeySize() As Integer Implements ICrypto.KeySize
        Dim aes As New RijndaelManaged()

        Return aes.KeySize
    End Function

    ' decrypts a string that was encrypted using the Encrypt method
    Public Function Decrypt(ByVal data As String) As String Implements ICrypto.Decrypt
        Try
            Dim inBytes() As Byte = Convert.FromBase64String(data)
            Dim mStream As New MemoryStream(inBytes, 0, inBytes.Length) ' instead of writing the decrypted text

            Dim aes As New RijndaelManaged()
            Dim cs As New CryptoStream(mStream, aes.CreateDecryptor(_key, _iv), CryptoStreamMode.Read)

            Dim sr As New StreamReader(cs)

            Return sr.ReadToEnd()
        Catch ex As Exception
            Throw ex
        End Try
    End Function

    ' Encrypts a given string
    Public Function Encrypt(ByVal data As String) As String Implements ICrypto.Encrypt
        Try
            Dim utf8 As New UTF8Encoding
            Dim inBytes() As Byte = utf8.GetBytes(data) ' ascii encoding uses 7 
'bytes for characters whereas the encryption uses 8 bytes, thus we use utf8
            Dim ms As New MemoryStream() 'instead of writing the encrypted 
'string to a filestream, I will use a memorystream

            Dim aes As New RijndaelManaged()
            Dim cs As New CryptoStream(ms, aes.CreateEncryptor(_key, _iv), CryptoStreamMode.Write)

            cs.Write(inBytes, 0, inBytes.Length) ' encrypt
            cs.FlushFinalBlock()

            Return Convert.ToBase64String(ms.GetBuffer(), 0, ms.Length)
        Catch ex As Exception
            Throw ex
        End Try
    End Function    
End Class

Here's the implementation. The first call creates the factor, the second creats the encryption/decryption object and passes the name of the algorithm given from a combobox. The rest is pretty self-explanatory.

Try
    Dim CryptographyFactory As New CryptoFactory()
    Dim Cryptographer As ICrypto = CryptographyFactory.MakeCryptographer(cboEncryption.SelectedItem)

    Dim etext As String = Cryptographer.Encrypt(txtInput.Text.ToString)
    txtEOutput.Text = etext

    Dim dtext As String = Cryptographer.Decrypt(etext)
    txtDOutput.Text = dtext
Catch ex As Exception
    MessageBox.Show(ex.Message, "Encryption Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try

Hope it clears up any wonders about symmetric encryption/decryption using .NET.