Base64加密加密和解密

2015-10-28 14:21:32 访问(1960) 赞(0) 踩(0)

using System;
using System.Collections.Generic;
using System.Text;

namespace eKing.GpsDataInfo.Helpers
{
    /// <summary>
    /// Base64加密加密和解密
    /// </summary>
    public class Base64Helper
    {
        ///<summary>
        /// Base64加密
        ///</summary>
        ///<paramname="Message"></param>
        ///<returns></returns>
        public static string Base64Code
            (
                string Message,
                System.Text.Encoding en
            )
        {
            if (en == null)
                en = System.Text.Encoding.Default;

            char[] Base64Code = new char[]{'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T',
'U','V','W','X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n',
'o','p','q','r','s','t','u','v','w','x','y','z','0','1','2','3','4','5','6','7',
'8','9','-','/','='};
            byte empty = (byte)0;

            System.Collections.ArrayList byteMessage
                =
                new System.Collections.ArrayList
                    (
                        en.GetBytes(Message)
                    );

            System.Text.StringBuilder outmessage;

            int messageLen = byteMessage.Count;

            //将字符分成3个字节一组，如果不足，则以0补齐
            int page = messageLen / 3;
            int use = 0;
            if ((use = messageLen % 3) > 0)
            {
                for (int i = 0; i < 3 - use; ++i)
                    byteMessage.Add(empty);

                ++page;
            }
            //将3个字节的每组字符转换成4个字节一组的。3个一组，一组一组变成4个字节一组
            //方法是：转换成ASCII码，按顺序排列24位数据，再把这24位数据分成4组，即每组6位。再在每组的的最高位前补两个0凑足一个字节。
            outmessage = new System.Text.StringBuilder(page * 4);
            for (int i = 0; i < page; ++i)
            {
                //取一组3个字节的组
                byte[] instr = new byte[3];
                instr[0] = (byte)byteMessage[i * 3];
                instr[1] = (byte)byteMessage[i * 3 + 1];
                instr[2] = (byte)byteMessage[i * 3 + 2];
                //六个位为一组，补0变成4个字节
                int[] outstr = new int[4];
                //第一个输出字节：取第一输入字节的前6位，并且在高位补0，使其变成8位（一个字节）
                outstr[0] = instr[0] >> 2;
                //第二个输出字节：取第一输入字节的后2位和第二个输入字节的前4位（共6位），并且在高位补0，使其变成8位（一个字节）
                outstr[1] = ((instr[0] & 0x03) << 4) ^ (instr[1] >> 4);
                //第三个输出字节：取第二输入字节的后4位和第三个输入字节的前2位（共6位），并且在高位补0，使其变成8位（一个字节）
                if (!instr[1].Equals(empty))
                    outstr[2] = ((instr[1] & 0x0f) << 2) ^ (instr[2] >> 6);
                else
                    outstr[2] = 64;
                //第四个输出字节：取第三输入字节的后6位，并且在高位补0，使其变成8位（一个字节）
                if (!instr[2].Equals(empty))
                    outstr[3] = (instr[2] & 0x3f);
                else
                    outstr[3] = 64;
                outmessage.Append(Base64Code[outstr[0]]);
                outmessage.Append(Base64Code[outstr[1]]);
                outmessage.Append(Base64Code[outstr[2]]);
                outmessage.Append(Base64Code[outstr[3]]);
            }

            return outmessage.ToString();
        }

        ///<summary>
        ///Base64解密
        ///</summary>
        ///<paramname="Message"></param>
        ///<returns></returns>
        public static string Base64Decode(string Message, System.Text.Encoding en)
        {
            if (en == null)
                en = System.Text.Encoding.Default;

            if ((Message.Length % 4) != 0)
            {
                throw new ArgumentException("不是正确的BASE64编码，请检查。", "Message");
            }
            if (!System.Text.RegularExpressions.Regex.IsMatch(Message, "^[A-Z0-9/-=]*$", System.Text.RegularExpressions.RegexOptions.IgnoreCase))
            {
                throw new ArgumentException("包含不正确的BASE64编码，请检查。", "Message");
            }
            string Base64Code = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-/=";
            int page = Message.Length / 4;
            System.Collections.ArrayList outMessage = new System.Collections.ArrayList(page * 3);
            char[] message = Message.ToCharArray();
            for (int i = 0; i < page; ++i)
            {
                byte[] instr = new byte[4];
                instr[0] = (byte)Base64Code.IndexOf(message[i * 4]);
                instr[1] = (byte)Base64Code.IndexOf(message[i * 4 + 1]);
                instr[2] = (byte)Base64Code.IndexOf(message[i * 4 + 2]);
                instr[3] = (byte)Base64Code.IndexOf(message[i * 4 + 3]);
                byte[] outstr = new byte[3];
                outstr[0] = (byte)((instr[0] << 2) ^ ((instr[1] & 0x30) >> 4));
                if (instr[2] != 64)
                {
                    outstr[1] = (byte)((instr[1] << 4) ^ ((instr[2] & 0x3c) >> 2));
                }
                else
                {
                    outstr[2] = 0;
                }
                if (instr[3] != 64)
                {
                    outstr[2] = (byte)((instr[2] << 6) ^ instr[3]);
                }
                else
                {
                    outstr[2] = 0;
                }
                outMessage.Add(outstr[0]);
                if (outstr[1] != 0)
                    outMessage.Add(outstr[1]);
                if (outstr[2] != 0)
                    outMessage.Add(outstr[2]);
            }
            byte[] outbyte = (byte[])outMessage.ToArray(Type.GetType("System.Byte"));
            return en.GetString(outbyte);
        }
    }
}