本文介绍使用XOR加密算法对数据进行加密， 这是一种很简单的算法，使用了尽量简单的VB编程方法，通俗易懂。我们可以采用更安全的算法如DES算法，IDEA算法等。各位如有任何见解，请不吝赐教。

在窗体中添加一RichTextBox，设置其Name属性为SourceFile，Multiline属性为True，ScrollBars属性为3－both。添加一MainMenu，设置一菜单项“文件”，其下有“打开”，“保存”，“加密”，“解密”，“算子”等子菜单项。
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
'解密过程，对xor算法而言，解密和加密过程是完全一样的
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("请输入加密算子", "设置加密算子")
End Sub
End Class