RIJNDAEL - symmetric block cipher

seguranca.cs

using System;  
using System.Collections.Generic;  
using System.Text;  
using System.Security.Cryptography;  
using System.IO;  
  
namespace Seguranca  
{  
    static class ClSeguranca  
    {  
        static string CONST_CHAVE = "Chave_Exemplo";  
          
        public static string Criptografar(string dados)  
        {  
            string chave = CONST_CHAVE;  
            byte[] b = Encoding.UTF8.GetBytes(dados);  
            byte[] pw = Encoding.UTF8.GetBytes(chave);  
  
            RijndaelManaged rm = new RijndaelManaged();  
            PasswordDeriveBytes pdb = new PasswordDeriveBytes(chave, new MD5CryptoServiceProvider().ComputeHash(pw));  
            rm.Key = pdb.GetBytes(32);  
            rm.IV = pdb.GetBytes(16);  
            rm.BlockSize = 128;  
            rm.Padding = PaddingMode.PKCS7;  
  
            MemoryStream ms = new MemoryStream();  
  
            CryptoStream cryptStream = new CryptoStream(ms, rm.CreateEncryptor(rm.Key, rm.IV), CryptoStreamMode.Write);  
            cryptStream.Write(b, 0, b.Length);  
            cryptStream.FlushFinalBlock();  
  
  
            return System.Convert.ToBase64String(ms.ToArray());   
  
        }  
  
        public static string Descriptografar(string  sDados)  
        {  
            string chave = CONST_CHAVE;  
            byte[] dados = System.Convert.FromBase64String(sDados);  
            byte[] pw = Encoding.UTF8.GetBytes(chave);  
  
            RijndaelManaged rm = new RijndaelManaged();  
            PasswordDeriveBytes pdb = new PasswordDeriveBytes(chave, new MD5CryptoServiceProvider().ComputeHash(pw));  
            rm.Key = pdb.GetBytes(32);  
            rm.IV = pdb.GetBytes(16);  
            rm.BlockSize = 128;  
            rm.Padding = PaddingMode.PKCS7;  
  
            MemoryStream ms = new MemoryStream(dados, 0, dados.Length);  
  
            CryptoStream cryptStream = new CryptoStream(ms, rm.CreateDecryptor(rm.Key, rm.IV), CryptoStreamMode.Read);  
            StreamReader sr = new StreamReader(cryptStream);  
  
            return sr.ReadToEnd();  
          
        }  
    }  
}