字符串加密

//方法一
//须添加对System.Web的引用
//using System.Web.Security;
/// 
/// SHA1加密字符串
/// 
/// 源字符串
/// 加密后的字符串
public string SHA1(string source)
{
    return FormsAuthentication.HashPasswordForStoringInConfigFile(source, "SHA1");
}
/// 
/// MD5加密字符串
/// 
/// 源字符串
/// 加密后的字符串
public string MD5(string source)
{
    return FormsAuthentication.HashPasswordForStoringInConfigFile(source, "MD5");;
}

//方法二(可逆加密解密)：
//using System.Security.Cryptography;
public string Encode(string data)
{
    byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(KEY_64);
    byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(IV_64);
    DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
    int i = cryptoProvider.KeySize;
    MemoryStream ms = new MemoryStream();
    CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateEncryptor(byKey, byIV), CryptoStreamMode.Write);
    StreamWriter sw = new StreamWriter(cst);
    sw.Write(data);
    sw.Flush();
    cst.FlushFinalBlock();
    sw.Flush();
    return Convert.ToBase64String(ms.GetBuffer(), 0, (int)ms.Length);
}
public string Decode(string data)
{
    byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(KEY_64);
    byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(IV_64);
    byte[] byEnc;
    try
    {
        byEnc = Convert.FromBase64String(data);
    }
    catch
    {
        return null;
    }
    DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
    MemoryStream ms = new MemoryStream(byEnc);
    CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateDecryptor(byKey, byIV), CryptoStreamMode.Read);
    StreamReader sr = new StreamReader(cst);

//方法三(MD5不可逆)：
//using System.Security.Cryptography;
//MD5不可逆加密
//32位加密
public string GetMD5_32(string s, string _input_charset)
{
    MD5 md5 = new MD5CryptoServiceProvider();
    byte[] t = md5.ComputeHash(Encoding.GetEncoding(_input_charset).GetBytes(s));
    StringBuilder sb = new StringBuilder(32);
    for (int i = 0; i  KeyLength)
        sTemp = sTemp.Substring(0, KeyLength);
    else if (sTemp.Length  IVLength)
        sTemp = sTemp.Substring(0, IVLength);
    else if (sTemp.Length