asp.net encryption and decryption class

      using System.Web.Security; 
    using System.Security.Cryptography; 
    using System.Text; 
    using System.IO;

public class EncryptHelper
{
        // 提供8个字符作为DES密钥（程序自动截取前8个字符） 
        private static string key = "admin10000.com";
        /// <summary>
        /// DES对称加密解密的密钥
        /// </summary> 
        public static string Key
        {
                get
                {
                        return key;
                }
                set
                {
                        key = value;
                }
        }
        /// <summary>
        /// MD5 加密（不可逆加密）
        /// </summary>
        /// <param name="pass">要加密的原始字串</param>
        /// <returns></returns> 
        public static string MD5Encrypt(string pass)
        {    
                System.Security.Cryptography.MD5 md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
                byte[] bytResult = md5.ComputeHash(System.Text.Encoding.UTF8.GetBytes(pass));
                md5.Clear();
                string strResult = BitConverter.ToString(bytResult);
                strResult = strResult.Replace("-", "");
                return strResult;        
                /* 另一种方法
                pass = FormsAuthentication.HashPasswordForStoringInConfigFile(pass, "MD5");
                return pass;
                */    
        }
        /// <summary>
        /// SHA1 加密（不可逆加密）
        /// </summary>
        /// <param name="pass">要加密的原始字串</param>
        /// <returns></returns> 
        public static string SHA1Encrypt(string pass)
        {
                System.Security.Cryptography.SHA1 sha1 = new System.Security.Cryptography.SHA1CryptoServiceProvider();
                byte[] bytResult = sha1.ComputeHash(System.Text.Encoding.UTF8.GetBytes(pass));
                sha1.Clear();
                string strResult = BitConverter.ToString(bytResult);
                strResult = strResult.Replace("-", "");
                return strResult;
                /* 另一种方法
                pass = FormsAuthentication.HashPasswordForStoringInConfigFile(pass, "SHA1");
                return pass;
                */
        }
        /// <summary>
        /// DES加密字符串
        /// </summary>
        /// <param name="encryptString">待加密的字符串</param>
        /// <returns>加密成功返回加密后的字符串，失败返回源串</returns> 
        public static string DESEncrypt(string encryptString)
        {
                try
                {
                        byte[] rgbKey = Encoding.UTF8.GetBytes(key.Substring(0, 8));
                        byte[] rgbIV = rgbKey;
                        byte[] inputByteArray = Encoding.UTF8.GetBytes(encryptString);
                        DESCryptoServiceProvider dCSP = new DESCryptoServiceProvider();
                        MemoryStream mStream = new MemoryStream();
                        CryptoStream cStream = new CryptoStream(mStream, dCSP.CreateEncryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
                        cStream.Write(inputByteArray, 0, inputByteArray.Length);
                        cStream.FlushFinalBlock();
                        cStream.Close();
                        return Convert.ToBase64String(mStream.ToArray());
                }
                catch
                {
                        return encryptString;
                }
        }
        /// <summary>
        /// DES解密字符串
        /// </summary>
        /// <param name="decryptString">待解密的字符串</param>
        /// <returns>解密成功返回解密后的字符串，失败返源串</returns> 
        public static string DESDecrypt(string decryptString)
        {
                try
                {
                        byte[] rgbKey = Encoding.UTF8.GetBytes(key.Substring(0, 8));
                        byte[] rgbIV = rgbKey;
                        byte[] inputByteArray = Convert.FromBase64String(decryptString);
                        DESCryptoServiceProvider DCSP = new DESCryptoServiceProvider();
                        MemoryStream mStream = new MemoryStream();
                        CryptoStream cStream = new CryptoStream(mStream, DCSP.CreateDecryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
                        cStream.Write(inputByteArray, 0, inputByteArray.Length);
                        cStream.FlushFinalBlock();
                        cStream.Close();
                        return Encoding.UTF8.GetString(mStream.ToArray());
                }
                catch
                {
                        return decryptString;
                }
        }
        /// <summary>
        /// 将普通字符串编码为BASE64字串
        /// </summary>
        /// <param name="str">源字符串</param>
        /// <returns></returns> 
        public static string Base64Encode(string str)
        {
                return Convert.ToBase64String(Encoding.UTF8.GetBytes(str));
        }
        /// <summary>
        /// 解码BASE64字串
        /// </summary>
        /// <param name="str">Base64字串</param>
        /// <returns></returns> 
        public static string Base64Decode(string base64Str)
        {
                return Encoding.UTF8.GetString(Convert.FromBase64String(base64Str));
        }
}