message-digest algorithm 5

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

namespace Ecan.Crypt
{
    public class EcanCryptography
    {
        /*MD5是message-digest algorithm 5（信息-摘要算法）的缩写，
         * 被广泛用于加密和解密技术上，它可以说是文件的“数字指纹”。
         * 任何一个文件，无论是可执行程序、图像文件、临时文件或者其他任何类型的文件，
         * 也不管它体积多大，都有且只有一个独一无二的MD5信息值，并且如果这个文件被修改过，
         * 它的MD5值也将随之改变。因此，我们可以通过对比同一文件的MD5值，
         * 来校验这个文件是否被“篡改”过。*/

        /// <summary>
        /// MD5加密函数
        /// </summary>
        /// <param name="str">要加密的字符串</param>
        /// <returns>加密后的字符串</returns>
        ///
        public string md5_Encode(string str)
        {
            MD5 m = new MD5CryptoServiceProvider();
            byte[] data = Encoding.Default.GetBytes(str);
            byte[] result = m.ComputeHash(data);
            string ret1 = "";
            try
            {
                for (int j = ; j < result.Length; j++)
                {
                    ret1 += result[j].ToString("x").PadLeft(, '');
                }
                return ret1;
            }
            catch
            {
                return str;
            }
        }

        /// <summary>
        /// 简单加密函数
        /// </summary>
        /// <param name="str">要加密的字符串</param>
        /// <returns>返回加密后的字符串</returns>
        ///
        public static string simple_Encode(string str)
        {
            string s = "";
            try
            {
                for (int i = ; i < str.Length; i++)
                {
                    s += (char)(str[i] +  -  * );
                }
                return s;
            }
            catch
            {
                return str;
            }
        }

        /// <summary>
        /// 简单解密函数
        /// </summary>
        /// <param name="str">要解密的字符串</param>
        /// <returns>返回解密后的字符串</returns>
        ///
        public static string simple_Decode(string str)
        {
            string s = "";
            try
            {
                for (int i = ; i < str.Length; i++)
                {
                    s += (char)(str[i] -  +  * );
                }
                return s;
            }
            catch
            {
                return str;
            }
        }

        //默认密钥向量
        private static byte[] Keys = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };

        /// <summary>
        /// 对称加密法加密函数
        /// </summary>
        /// <param name="encryptString">待加密的字符串</param>
        /// <param name="encryptKey">加密密钥,要求为8位</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 symmetry_Encode(string encryptString, string encryptKey)
        {
            try
            {
                byte[] rgbKey = Encoding.UTF8.GetBytes(encryptKey.Substring(, ));
                byte[] rgbIV = Keys;
                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, , inputByteArray.Length);
                cStream.FlushFinalBlock();
                return Convert.ToBase64String(mStream.ToArray());
            }
            catch
            {
                return encryptString;
            }
        }

        /// <summary>
        /// 对称加密法解密函数
        /// </summary>
        /// <param name="decryptString">待解密的字符串</param>
        /// <param name="decryptKey">解密密钥,要求为8位,和加密密钥相同</param>
        /// <returns>解密成功返回解密后的字符串，失败返源串</returns>

        public static string symmetry_Decode(string decryptString, string decryptKey)
        {
            try
            {
                byte[] rgbKey = Encoding.UTF8.GetBytes(decryptKey);
                byte[] rgbIV = Keys;
                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, , inputByteArray.Length);
                cStream.FlushFinalBlock();
                return Encoding.UTF8.GetString(mStream.ToArray());
            }
            catch
            {
                return decryptString;
            }
        }
    }
}