常用的加密解密（DES，RSA）

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

    /// <summary>
    /// DES加密
    /// </summary>
    /// <param name="input">待加密的字符串</param>
    /// <param name="key">加密密鑰</param>
    /// <returns></returns>
    public static string Encrypt(string EncryptString, byte[] Key, byte[] IV)
    {
        //byte[] rgbKey = Encoding.UTF8.GetBytes(key.Substring(0, 8));
        byte[] inputByteArray = Encoding.UTF8.GetBytes(EncryptString);
        DESCryptoServiceProvider des = new DESCryptoServiceProvider();
        MemoryStream mStream = new MemoryStream();
        CryptoStream cStream = new CryptoStream(mStream, des.CreateEncryptor(Key, IV), CryptoStreamMode.Write);
        cStream.Write(inputByteArray, 0, inputByteArray.Length);
        cStream.FlushFinalBlock();
        return Convert.ToBase64String(mStream.ToArray());
    }
    /// <summary>
    /// DES解密
    /// </summary>
    /// <param name="input">待解密的字符串</param>
    /// <param name="key">解密密鑰,要求爲8位,和加密密鑰相同</param>
    /// <returns>解密成功返回解密後的字符串,失敗返源串</returns>
    public static string Decrypt(string DecryptString, byte[] Key, byte[] IV)
    {
        try
        {
            //byte[] rgbKey = Encoding.UTF8.GetBytes(Key);
            byte[] inputByteArray = Convert.FromBase64String(DecryptString);
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();

            MemoryStream mStream = new MemoryStream();
            CryptoStream cStream = new CryptoStream(mStream, des.CreateDecryptor(Key, IV), CryptoStreamMode.Write);
            cStream.Write(inputByteArray, 0, inputByteArray.Length);
            cStream.FlushFinalBlock();
            return Encoding.UTF8.GetString(mStream.ToArray());
        }
        catch
        {
            return "";
        }
    }
}
/// <summary>
/// RSA加解密算法
/// </summary>
public class RSA
{
    /// <summary>
    /// RSA加密函數
    /// </summary>
    /// <param name="xmlPublicKey">說明KEY必須是XML的行式,返回的是字符串</param>
    /// <param name="EncryptString"></param>
    /// <returns></returns>
    public string Encrypt(string xmlPublicKey, string EncryptString)
    {
        byte[] PlainTextBArray;
        byte[] CypherTextBArray;
        string Result;
        RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
        rsa.FromXmlString(xmlPublicKey);
        PlainTextBArray = (new UnicodeEncoding()).GetBytes(EncryptString);
        CypherTextBArray = rsa.Encrypt(PlainTextBArray, false);
        Result = Convert.ToBase64String(CypherTextBArray);
        return Result;
    }
    /// <summary>
    /// RSA解密函數
    /// </summary>
    /// <param name="xmlPrivateKey"></param>
    /// <param name="DecryptString"></param>
    /// <returns></returns>
    public string Decrypt(string xmlPrivateKey, string DecryptString)
    {
        byte[] PlainTextBArray;
        byte[] DypherTextBArray;
        string Result;
        RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
        rsa.FromXmlString(xmlPrivateKey);
        PlainTextBArray = Convert.FromBase64String(DecryptString);
        DypherTextBArray = rsa.Decrypt(PlainTextBArray, false);
        Result = (new UnicodeEncoding()).GetString(DypherTextBArray);
        return Result;
    }

    /// <summary>
    /// 產生RSA的密鑰
    /// </summary>
    /// <param name="xmlKeys">私鑰</param>
    /// <param name="xmlPublicKey">公鑰</param>
    public void RSAKey(out string xmlKeys, out string xmlPublicKey)
    {
        RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
        xmlKeys = rsa.ToXmlString(true);
        xmlPublicKey = rsa.ToXmlString(false);
    }