using System;

using System.Security.Cryptography;

using System.Text;

using Microsoft.VisualBasic;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(Criptografia.Criptografar("banana", "minhachave123"));

    }

}

​

public static class Criptografia

    {

        private static string Hex(string value)

        {

            try

            {

                uint uiDecimal = checked(Convert.ToUInt32(value));

                return String.Format("{0:x2}", uiDecimal);

            }

            catch(OverflowException oExp)

            {

                throw new ApplicationException(oExp.Message);

            }

        }

​

        private static uint UndoHex(string value)

        {

            try

            {

                uint uiHex = Convert.ToUInt32(value, 16);

                return uiHex;

            }

            catch(OverflowException oExp)

            {

                throw new ApplicationException(oExp.Message);

            }

        }

​

        public static string Decriptografar(string text, string key)

        {

            try

            {

                string sTextoTratado = string.Empty;

                int iTextoPos;

                int iChavePos = 0;

​

                int iTamChave = key.Length;

​

                uint iCompoeCod = UndoHex(Microsoft.VisualBasic.Strings.Left(text, 2));

​

                for(iTextoPos = 3; iTextoPos <= text.Length; iTextoPos += 2)

                {

                    uint iTextoAsc = UndoHex(Strings.Mid(text, iTextoPos, 2));

                    if(iChavePos < iTamChave) iChavePos++;

                    else iChavePos = 1;

                    uint iTmpTextoAsc = iTextoAsc ^ (uint) Strings.Asc(Strings.Mid(key, iChavePos, 1));

                    if(iTmpTextoAsc <= iCompoeCod) iTmpTextoAsc = 255 + iTmpTextoAsc - iCompoeCod;

                    else iTmpTextoAsc -= iCompoeCod;

                    sTextoTratado += Strings.Chr((int) iTmpTextoAsc);

​

                    iCompoeCod = iTextoAsc;

                }

                return sTextoTratado;

            }

            catch

            {

                return "";

            }

        }

​

        public static string Criptografar(string text, string key)

        {

            try

            {

                string sTemp;

                var oRandom = new Random(DateTime.Now.Millisecond);

                int iTextoPos;

                uint iTextoAsc;

                int iChavePos = 0;

​

                int iTamChave = key.Length;

                int iMultiplication = ((DateTime.Now.Year*5) + ((int) DateTime.Now.DayOfWeek*DateTime.Now.Hour) + DateTime.Now.Minute + DateTime.Now.Second);

                while(iMultiplication < 10000)

                {

                    iMultiplication += DateTime.Now.Year;

                }

                double a = oRandom.NextDouble();

                var iCompoeCod = (uint) ((a*iMultiplication%255) + 1);

​

                while(iCompoeCod < 16)

                {

                    iCompoeCod += (uint) DateTime.Now.Second;

                }

​

                //sTextoTratado = Microsoft.VisualBasic.Conversion.Hex(iCompoeCod);

                string sTextoTratado = Hex(iCompoeCod.ToString());

​

                for(iTextoPos = 0; iTextoPos <= text.Length - 1; iTextoPos++)

                {

                    string sChar = text.Substring(iTextoPos, 1);

                    iTextoAsc = (uint) ((Strings.Asc(sChar) + iCompoeCod)%255);

​

                    if(iChavePos < iTamChave) iChavePos = iChavePos + 1;

                    else iChavePos = 1;

                    iTextoAsc = (uint) (iTextoAsc ^ Strings.Asc(Strings.Mid(key, iChavePos, 1)));

​

                    sTemp = Hex(iTextoAsc.ToString());

​

                    if(sTemp.Length == 1) sTemp = "0" + sTemp;

                    sTextoTratado = sTextoTratado + sTemp;

                    iCompoeCod = iTextoAsc;

                }

                return sTextoTratado;

            }

            catch

            {

                return "";

            }

        }

​

        /// <summary>

        ///   Calcula o Hash (MD5) para uma string de entrada Text. E retorna o HASH em Hexadecimal.

        /// </summary>

        /// <param name = "text">String de entrada o qual deseja calcular o Hash</param>

        /// <returns></returns>

        public static string MD5Hash(string text)

        {

            try

            {

                string result = "";

                if (text != "")

                {

                    // step 1, calculate MD5 hash from input

                    MD5 md5 = MD5.Create();

                    byte[] inputBytes = Encoding.ASCII.GetBytes(text);

                    byte[] hash = md5.ComputeHash(inputBytes);

​

                    // step 2, convert byte array to hex string

                    var sb = new StringBuilder();

                    for (int i = 0; i < hash.Length; i++)

                    {

                        sb.Append(hash[i].ToString("X2"));

                    }

                    result = sb.ToString();

                }

​

                return result;

            }

            catch(Exception ex)

            {

            }

            return null;

        }

    }