Как кодировать информацию в текстовом файле

Imports System.IO
Imports System.Text
Imports System.Security.Cryptography
 
Public Class Form1
 
 
  ' Закодировать
  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim rd As New RijndaelManaged
 
    Dim md5 As New MD5CryptoServiceProvider
    Dim key() As Byte = md5.ComputeHash(Encoding.UTF8.GetBytes(TextBox2.Text))
 
    md5.Clear()
    rd.Key = key
    rd.GenerateIV()
 
    Dim iv() As Byte = rd.IV
    Dim ms As New MemoryStream
 
    ms.Write(iv, 0, iv.Length)
 
    Dim cs As New CryptoStream(ms, rd.CreateEncryptor, CryptoStreamMode.Write)
    Dim data() As Byte = System.Text.Encoding.UTF8.GetBytes(TextBox1.Text)
 
    cs.Write(data, 0, data.Length)
    cs.FlushFinalBlock()
 
    Dim encdata() As Byte = ms.ToArray()
    TextBox3.Text = Convert.ToBase64String(encdata)
    cs.Close()
    rd.Clear()
    TextBox1.Text = ""
  End Sub
 
 
  ' Раскодировать
  Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
    Dim rd As New RijndaelManaged
    Dim rijndaelIvLength As Integer = 16
    Dim md5 As New MD5CryptoServiceProvider
    Dim key() As Byte = md5.ComputeHash(Encoding.UTF8.GetBytes(TextBox2.Text))
 
    md5.Clear()
 
    Dim encdata() As Byte = Convert.FromBase64String(TextBox3.Text)
    Dim ms As New MemoryStream(encdata)
    Dim iv(15) As Byte
 
    ms.Read(iv, 0, rijndaelIvLength)
    rd.IV = iv
    rd.Key = key
 
    Dim cs As New CryptoStream(ms, rd.CreateDecryptor, CryptoStreamMode.Read)
 
    Dim data(ms.Length - rijndaelIvLength) As Byte
    Dim i As Integer = cs.Read(data, 0, data.Length)
 
    TextBox1.Text = System.Text.Encoding.UTF8.GetString(data, 0, i)
    cs.Close()
    rd.Clear()
  End Sub
End Class

Public Class Form1
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim Key(255) As Byte
        GenKey(Key)
        Dim EncodeText = Encode("QWERT", Key)
        MsgBox("Закодировано: " & EncodeText)
        MsgBox("Раскодировано: " & DeCode(EncodeText, Key))
    End Sub
 
    'Генератор ключа.
    Sub GenKey(ByRef Key As Array)
        For i = 0 To 255 Step 1
            Randomize()
            Key(i) = Rnd() * 255
        Next
    End Sub
 
    'Закодировать.
    Function Encode(ByVal Text As String, ByVal Key As Array) As String
        Dim C As Integer = 0
        For i = 1 To Text.Length Step 1
            Encode = Encode & Chr(Key(C) + Asc(Mid(Text, i, 1)) + 255 * (Key(C) + Asc(Mid(Text, i, 1)) > 255))
            C = C + 1
            If C = 256 Then
                C = 0
            End If
        Next
    End Function
 
    'Раскодировать.
    Function DeCode(ByVal Text As String, ByVal Key As Array) As String
        Dim C As Integer = 0
        For i = 1 To Text.Length Step 1
            DeCode = DeCode & Chr(Asc(Mid(Text, i, 1)) - 255 * (Asc(Mid(Text, i, 1)) < Key(C)) - Key(C))
            C = C + 1
            If C = 256 Then
                C = 0
            End If
        Next
    End Function
 
End Class

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim Key() As Byte = {2, 4, 5, 63, 35, 11} 'Как пример.
        Dim EncodeText = Encode("QWERT", Key)
        MsgBox("Закодировано: " & EncodeText)
        MsgBox("Раскодировано: " & DeCode(EncodeText, Key))
    End Sub