C#加密解密方法

这可是我们齐老师收集的。非常有用。比如你写了一个XXX管理系统，它要把用户的一些软件激活码保存在本地的INI格式配置文件中，如果你使用明文的话，肯定用不了两天，百度上就会满是你的软件的破解码了。哈哈，事实就是这样，好好学习加密之法吧：

1、方法一 (不可逆加密)

    public string EncryptPassword(string PasswordString,string PasswordFormat ) 
    { 
       string encryptPassword = null;
       if (PasswordFormat="SHA1")
       { 
          encryptPassword=FormsAuthortication.HashPasswordForStoringInConfigFile(PasswordString ,"SHA1"); 
       } 
       elseif (PasswordFormat="MD5") 
       { 
          encryptPassword=FormsAuthortication.HashPasswordForStoringInConfigFile(PasswordString ,"MD5"); 
       }
         return encryptPassword ;
    }
2、方法二 (可逆加密)

public interface IBindesh
    {
    string encode(string str);
    string decode(string str);
     }

    public class EncryptionDecryption : IBindesh
    {
        public string encode(string str)
         {
            string htext = "";

            for ( int i = 0; i < str.Length; i++)
            {
                htext = htext + (char) (str[i] + 10 - 1 * 2);
            }
            return htext;
     }

        public string decode(string str)
        {
            string dtext = "";

            for ( int i=0; i < str.Length; i++)
            {
                dtext = dtext + (char) (str[i] - 10 + 1*2);
            }
            return dtext;
        }

3、方法三 (可逆加密)

const string KEY_64 = "VavicApp";//注意了，是8个字符，64位

        const string IV_64 = "VavicApp"; 
        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);