using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;


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

namespace CommonObj.common
{
    public sealed class clsCustomEncryptionbk
    {
        //private static string key = "sfdjf48mdfdf3054";
        //private static string key = "sfdjf48mdfdf3054123";

        public clsCustomEncryptionbk()
        {
        }
        /// <summary>
        /// Mã hóa dựa trên thuật toán mã hóa 1 chiều MD5, 
        /// Sau khi mã hóa, sử dụng thuật toán encode Base64 để lưu dưới dạng Text
        /// </summary>
        /// <param name="plainText">Chuỗi cần mã hóa</param>
        /// <returns></returns>
        public static string EncryptUseMD5(string plainText)
        {
            string encrypted = null;
            MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
            byte[] pwdhash = hashmd5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(plainText));
            encrypted = Convert.ToBase64String(pwdhash);
            return encrypted;
        }
        /// <summary>
        /// Mã hóa dựa trên thuật toán mã hóa phức hợp, có thể giải mã sử dụng hàm Decrypt, 
        /// Sau khi mã hóa, sử dụng thuật toán encode Base64 để lưu dưới dạng Text
        /// </summary>
        /// <param name="plainText">Chuỗi cần mã hóa</param>
        /// <returns></returns>
        public static string Encrypt(string plainText,string key)
        {
            string encrypted = null;
            try
            {
                byte[] inputBytes = ASCIIEncoding.ASCII.GetBytes(plainText);
                byte[] pwdhash = null;
                MD5CryptoServiceProvider hashmd5;

                //generate an MD5 hash from the password. 
                //a hash is a one way encryption meaning once you generate
                //the hash, you cant derive the password back from it.
                hashmd5 = new MD5CryptoServiceProvider();
                pwdhash = hashmd5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(key));
                hashmd5 = null;

                // Create a new TripleDES service provider 
                TripleDESCryptoServiceProvider tdesProvider = new TripleDESCryptoServiceProvider();
                tdesProvider.Key = pwdhash;
                tdesProvider.Mode = CipherMode.ECB;

                encrypted = Convert.ToBase64String(
                    tdesProvider.CreateEncryptor().TransformFinalBlock(inputBytes, 0, inputBytes.Length));
            }
            catch (Exception e)
            {
                string str = e.Message;
                throw;
            }
            return encrypted;
        }
        /// <summary>
        /// Thực hiện giải mã một xâu ký tự
        /// </summary>
        /// <param name="encryptedString">Chuỗi đã mã hóa</param>
        /// <returns></returns>
        public static string Decrypt(string encryptedString,string key)
        {
            string decyprted = null;
            byte[] inputBytes = null;

            try
            {
                inputBytes = Convert.FromBase64String(encryptedString);
                byte[] pwdhash = null;
                MD5CryptoServiceProvider hashmd5;

                //generate an MD5 hash from the password. 
                //a hash is a one way encryption meaning once you generate
                //the hash, you cant derive the password back from it.
                hashmd5 = new MD5CryptoServiceProvider();
                pwdhash = hashmd5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(key));
                hashmd5 = null;

                // Create a new TripleDES service provider 
                TripleDESCryptoServiceProvider tdesProvider = new TripleDESCryptoServiceProvider();
                tdesProvider.Key = pwdhash;
                tdesProvider.Mode = CipherMode.ECB;

                decyprted = ASCIIEncoding.ASCII.GetString(
                    tdesProvider.CreateDecryptor().TransformFinalBlock(inputBytes, 0, inputBytes.Length));
            }
            catch
            {
                decyprted = "";
                
            }
            return decyprted;
        }
    }
}