字符串加密解密

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

namespace Util
{
    /// <summary>
    /// 字符串加密解密类。
    /// </summary>
    public sealed class StringSecurity
    {
        private StringSecurity() { }

 #region MD5 加密
 
 public string GetMD5String(string str)
        {
            MD5 md5 = new MD5CryptoServiceProvider();//new一个MD5对像
 //1,先将字符串编码成一个byte[]
            byte[] data = Encoding.Default.GetBytes(str);//Default是指默认的编码方式，也可以换成别的如Utf-8
 //2，再用MD5对像将byte[]加密，得到一个byte[]
            byte[] md5data = md5.ComputeHash(data);
            md5.Clear();
 //3,将byte[]叠加到一个StringBuilder，然后返回
            StringBuilder builder = new StringBuilder();
            for (int i = 0; i < md5data.Length - 1; i++)
            {
                Console.WriteLine(md5data[i].ToString());
                builder.Append(md5data[i].ToString("X2"));
            }
            return builder.ToString();
        }
 #endregion

        #region SHA1 加密

        /// <summary>
        /// 使用SHA1加密字符串。
        /// </summary>
        /// <param name="inputString">输入字符串。</param>
        /// <returns>加密后的字符串。（40个字符）</returns>
        public static string StringToSHA1Hash(string inputString)
        {
            SHA1CryptoServiceProvider sha1 = new SHA1CryptoServiceProvider();
            byte[] encryptedBytes = sha1.ComputeHash(Encoding.ASCII.GetBytes(inputString));
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < encryptedBytes.Length; i++)
            {
                sb.AppendFormat("{0:x2}", encryptedBytes[i]);
            }
            return sb.ToString();
        }

        #endregion

        #region DES 加密/解密

        private static byte[] key = ASCIIEncoding.ASCII.GetBytes("caikelun");
        private static byte[] iv = ASCIIEncoding.ASCII.GetBytes("12345678");

        /// <summary>
        /// DES加密。
        /// </summary>
        /// <param name="inputString">输入字符串。</param>
        /// <returns>加密后的字符串。</returns>
        public static string DESEncrypt(string inputString)
        {
            MemoryStream ms = null;
            CryptoStream cs = null;
            StreamWriter sw = null;

            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            try
            {
                ms = new MemoryStream();
                cs = new CryptoStream(ms, des.CreateEncryptor(key, iv), CryptoStreamMode.Write);
                sw = new StreamWriter(cs);
                sw.Write(inputString);
                sw.Flush();
                cs.FlushFinalBlock();
                return Convert.ToBase64String(ms.GetBuffer(), 0, (int)ms.Length);
            }
            finally
            {
                if (sw != null) sw.Close();
                if (cs != null) cs.Close();
                if (ms != null) ms.Close();
            }
        }

        /// <summary>
        /// DES解密。
        /// </summary>
        /// <param name="inputString">输入字符串。</param>
        /// <returns>解密后的字符串。</returns>
        public static string DESDecrypt(string inputString)
        {
            MemoryStream ms = null;
            CryptoStream cs = null;
            StreamReader sr = null;

            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            try
            {
                ms = new MemoryStream(Convert.FromBase64String(inputString));
                cs = new CryptoStream(ms, des.CreateDecryptor(key, iv), CryptoStreamMode.Read);
                sr = new StreamReader(cs);
                return sr.ReadToEnd();
            }
            finally
            {
                if (sr != null) sr.Close();
                if (cs != null) cs.Close();
                if (ms != null) ms.Close();
            }
        }

        #endregion

    }
}