本文介紹使用XOR加密算法對數據進行加密， 這是一種很簡單的算法，使用了盡量簡單的VB編程方法，通俗易懂。我們可以采用更安全的算法如DES算法，IDEA算法等。各位如有任何見解，請不吝賜教。

在窗體中添加一RichTextBox，設置其Name屬性為SourceFile，Multiline屬性為True，ScrollBars屬性為3－both。添加一MainMenu，設置一菜單項“文件”，其下有“打開”，“保存”，“加密”，“解密”，“算子”等子菜單項。
以下是大致的程序界面：



Public Class Form1
Inherits System.Windows.Forms.Form
Dim strNum As String
Private Sub Form1_Load(ByVal eventSender As System.Object, ByVal eventArgs As System.EventArgs) Handles MyBase.Load
strNum = "password"
End Sub

Private Sub Form1_Resize(ByVal eventSender As System.Object, ByVal eventArgs As System.EventArgs) Handles MyBase.Resize
SourceFile.Width = Form1.DefInstance.Width
SourceFile.Height = Form1.DefInstance.Height
End Sub
'解密過程，對xor算法而言，解密和加密過程是完全一樣的
Private Function XorOut(ByRef strNum As String, ByRef strText As String) As String
Dim i As Integer
Dim XorValue1 As Short
Dim XorValue2 As Short
Dim strResult As String
For i = 1 To Len(strText)
XorValue1 = Asc(Mid(strText, i, 1))
XorValue2 = Asc(Mid(strNum, (i Mod Len(strNum)) + 1, 1))
strResult = strResult & Chr(XorValue1 Xor XorValue2)
Next
XorOut = strResult
End Function

Private Sub MenuDeEncrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MenuDeEncrypt.Click
SourceFile.Text = XorOut(strNum, (SourceFile.Text))
End Sub

Private Sub MenuEncrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MenuEncrypt.Click
SourceFile.Text = XorOut(strNum, (SourceFile.Text))
End Sub

Private Sub MenuOpen_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MenuOpen.Click
Dim openFile1 As New OpenFileDialog
' Determine whether the user selected a file from the OpenFileDialog.
If (openFile1.ShowDialog() = DialogResult.OK) _
And (openFile1.FileName.Length > 0) Then

' Load the contents of the file into the RichTextBox.
SourceFile.LoadFile(openFile1.FileName, _
RichTextBoxStreamType.PlainText)
End If
End Sub

Private Sub MenuSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MenuSave.Click
' Create a SaveFileDialog to request a path and file name to save to.
Dim saveFile1 As New SaveFileDialog

' Initialize the SaveFileDialog to specify the RTF extension for the file.
'saveFile1.DefaultExt = "*.rtf"
'saveFile1.Filter = "RTF Files|*.rtf"

' Determine if the user selected a file name from the saveFileDialog.
If (saveFile1.ShowDialog() = DialogResult.OK) _
And (saveFile1.FileName.Length) > 0 Then

' Save the contents of the RichTextBox into the file.
SourceFile.SaveFile(saveFile1.FileName, _
RichTextBoxStreamType.PlainText)
End If
End Sub

Private Sub MenuNum_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MenuNum.Click
strNum = InputBox("請輸入加密算子", "設置加密算子")
End Sub
End