using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace EncryptDecrypt

{ 

    public class EncryptDecrypt

    {

        const char fillchar = '=';

        static string cvt = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

        //Method to encrypt data

        static public string Encode(string data)

        {

            int i;

            int c;

            int len = data.Length;

            string ret = "";

            for (i = 0; i < len; ++i)

            {

               c = (data >> 2) & 0x3f;

                ret += cvt[c];

                c = (data << 4) & 0x3f;

                if (++i < len)

                    c |= (data >> 4) & 0x0f;

                ret += cvt[c];

                if (i < len)

                {

                    c = (data << 2) & 0x3f;

                    if (++i < len)

                        c |= (data >> 6) & 0x03;

                    ret += cvt[c];

                }

                else

               {

                    ++i;

                    ret += fillchar;

                }

                if (i < len)

                {

                   c = data & 0x3f;

                    ret += cvt[c];

                }

                else

                {

                    ret += fillchar;

                }

            }

            return (ret);

        }



       //Method to decrypt the data

        static public string Decode(string data)

        {

            string ret = "";

            int i;

            char c;

            char c1;

            int len = data.Length;

            for (i = 0; i < len; ++i)

            {

                c = (char)cvt.IndexOf(data);

                ++i;

                c1 = (char)cvt.IndexOf(data);

                c = ((char)((c << 2) | ((c1 >> 4) & 0x3)));

                ret += c;

                if (++i < len)

                {

                   c = data;

                    if (fillchar == c)

                        break;

                    c = (char)cvt.IndexOf(c);

                    c1 = (char)(((c1 << 4) & 0xf0) | ((c >> 2) & 0xf));

                    ret += c1;

                }

                if (++i < len)

                {

                   c1 = data;

                    if (fillchar == c1)

                        break;

                    c1 = (char)cvt.IndexOf(c1);

                    c = (char)(((c << 6) & 0xc0) | c1);

                    ret += c;

                }

           }

            return (ret);

        }

    }

}