Public Class EncryptionForm

   ' using the substitution cipher
   Private Sub SubstitutionCipher()

      ' normal alphabet String
      Dim normalAlphabet As String = _
         "abcdefghijklmnopqrstuvwxyz .!?,"

      ' substitution alphabet String
      Dim cipherAlphabet As String = _
         "cdefg.hijk!lmn opqr?stuv,wxyzab"

      Dim index1 As Integer ' index variable for For...Next loop
      Dim index2 As Integer ' inner index variable
      Dim plain As String = plainTextBox.Text ' String entered by the user
      Dim cipher As String ' encrypted String

      cipherTextLabel.Text = "" ' clear output TextBox
      plain = plain.ToLower() ' make characters lowercase

      For index1 = 1 To plain.Length  'go through user input string

         For index2 = 1 To plain.Length  ' go through the cipher alphabet string the length of the input string
            cipher &= cipherAlphabet.Chars(index2) ' append character to string
         Next
         cipherTextLabel.Text = cipher ' output new string to label
      Next
   End Sub ' SubstitutionCipher