C# 几个加密算法

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class EncryptPassword: System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Response.Write(encryptPassword("0490", "SHA1") + "," + encryptPassword("0490", "MD5")+"<br/>");

        Label1.Text = encryptPassword("0490","");
        Response.Write(Decode(Label1.Text));
    }

    /// <summary>
    /// SHA1,MD5加密
    /// </summary>
    /// <param name="PassWords"></param>
    /// <param name="passFormat"></param>
    /// <returns></returns>
    string encryptPassword(string PassWords, string passFormat)
    {
        string Encrypt = string.Empty;
        if (passFormat == "SHA1")
        {
            Encrypt = FormsAuthentication.HashPasswordForStoringInConfigFile(PassWords, passFormat);
        }
        else if (passFormat == "MD5")
        {
            Encrypt = FormsAuthentication.HashPasswordForStoringInConfigFile(PassWords, passFormat);
        }
         return Encrypt;
    }

    /// <summary>
    /// 按位或运算加密
    /// </summary>
    /// <param name="PassWords"></param>
    /// <returns></returns>
    string Encode(string PassWords)
    {
        string Encrypt = string.Empty;
        for (int i = 0; i < PassWords.Length; i++)
        {
            Encrypt += (char)(PassWords[i] + 50 - 1 * 3);  //此处为自己提供的密钥
        }
        return Encrypt;
    }
    /// <summary>
    /// 按位或运算解密
    /// </summary>
    /// <param name="PassWords"></param>
    /// <returns></returns>
    string Decode(string PassWords)
    {
        string Encrypt = string.Empty;
        for (int i = 0; i < PassWords.Length; i++)
        {
            Encrypt += (char)(PassWords[i] - 50 + 1 * 3);//此处为自己提供的密钥
        }
        return Encrypt;
    }
}