using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Linq; 
using System.Text; 
using System.Windows.Forms; 
namespace PRanDataEncrypt 
{ 
public partial class Form1 : Form 
{ 
public Form1() 
{ 
InitializeComponent(); 
} 
private void button1_Click(object sender, EventArgs e) 
{ 
if (textBox3.Text != "") 
{ 
if (DecryptPwd(textBox3.Text) == textBox2.Text) 
MessageBox.Show("用戶登錄成功！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information); 
else 
MessageBox.Show("用戶密碼錯誤！", "錯誤", MessageBoxButtons.OK, MessageBoxIcon.Error); 
} 
} 

private void button2_Click(object sender, EventArgs e) 
{ 
textBox1.Text = textBox2.Text = textBox3.Text = string.Empty; 
textBox2.Focus(); 
} 

private void textBox2_TextChanged(object sender, EventArgs e) 
{ 
textBox3.Text = EncryptPwd(textBox2.Text); 
} 

//定義加密用戶密碼所用的偽隨機數 
private string randStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz"; 
#region 使用偽隨機數加密用戶登錄密碼 
/// <summary> 
/// 使用偽隨機數加密用戶登錄密碼 
/// </summary> 
/// <param name="str">用戶登錄密碼</param> 
/// <returns>加密后的用戶登錄密碼</returns> 
private string EncryptPwd(string str) 
{ 
byte[] btData = Encoding.Default.GetBytes(str); 
int j, k, m; 
int len = randStr.Length; 
StringBuilder sb = new StringBuilder(); 
Random rand = new Random(); 
for (int i = 0; i < btData.Length; i++) 
{ 
j = (byte)rand.Next(6); 
btData[i] = (byte)((int)btData[i] ^ j); 
k = (int)btData[i] % len; 
m = (int)btData[i] / len; 
m = m * 8 + j; 
sb.Append(randStr.Substring(k, 1) + randStr.Substring(m, 1)); 
} 
return sb.ToString(); 
} 
#endregion 
#region 解密用戶登錄密碼 
/// <summary> 
/// 解密用戶登錄密碼 
/// </summary> 
/// <param name="str">經過加密的用戶登錄密碼</param> 
/// <returns>解密后的用戶登錄密碼</returns> 
private string DecryptPwd(string str) 
{ 
try 
{ 
int j, k, m, n = 0; 
int len = randStr.Length; 
byte[] btData = new byte[str.Length / 2]; 
for (int i = 0; i < str.Length; i += 2) 
{ 
k = randStr.IndexOf(str[i]); 
m = randStr.IndexOf(str[i + 1]); 
j = m / 8; 
m = m - j * 8; 
btData[n] = (byte)(j * len + k); 
btData[n] = (byte)((int)btData[n] ^ m); 
n++; 
} 
return Encoding.Default.GetString(btData); 
} 
catch { return ""; } 
} 
#endregion 
} 
}