A continuación mostramos las funciones cifrarTextoAES y descifrarTextoAES para cifrar/descifrar (encriptar/desencriptar) una cadena de texto usando el método Advanced Encryption Standard (AES) ó Rijndael. Mostramos el código completo de la clase "cifrarAES.cs". Las funciones de cifrado y descifrado permitirán elegir el algoritmo hash de encriptación (MD5, SHA1) y el tamaño de la clave: 128, 192 o 256.

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

namespace AjpdSoftIndexarTextoFicherosPDF
{
    class cifrarAES
    {
        public string cifrarTextoAES (string textoCifrar, string palabraPaso, 
            string valorRGBSalt, string algoritmoEncriptacionHASH, 
            int iteraciones, string vectorInicial, int tamanoClave)
        {
            try
            {
                byte[] InitialVectorBytes = Encoding.ASCII.GetBytes(vectorInicial);
                byte[] saltValueBytes = Encoding.ASCII.GetBytes(valorRGBSalt);
                byte[] plainTextBytes = Encoding.UTF8.GetBytes(textoCifrar);

                PasswordDeriveBytes password = 
                    new PasswordDeriveBytes(palabraPaso, saltValueBytes, 
                        algoritmoEncriptacionHASH, iteraciones);

                byte[] keyBytes = password.GetBytes(tamanoClave / 8);

                RijndaelManaged symmetricKey = new RijndaelManaged();

                symmetricKey.Mode = CipherMode.CBC;

                ICryptoTransform encryptor = 
                    symmetricKey.CreateEncryptor(keyBytes, InitialVectorBytes);

                MemoryStream memoryStream = new MemoryStream();

                CryptoStream cryptoStream = 
                    new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write);

                cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);

                cryptoStream.FlushFinalBlock();

                byte[] cipherTextBytes = memoryStream.ToArray();

                memoryStream.Close();
                cryptoStream.Close();

                string textoCifradoFinal = Convert.ToBase64String(cipherTextBytes);

                return textoCifradoFinal;
            }
            catch
            {                
                return null;
            }
        }


        public string descifrarTextoAES (string textoCifrado, string palabraPaso, 
            string valorRGBSalt, string algoritmoEncriptacionHASH, 
            int iteraciones, string vectorInicial, int tamanoClave)
        {
            try
            {
                byte[] InitialVectorBytes = Encoding.ASCII.GetBytes(vectorInicial);
                byte[] saltValueBytes = Encoding.ASCII.GetBytes(valorRGBSalt);

                byte[] cipherTextBytes = Convert.FromBase64String(textoCifrado);

                PasswordDeriveBytes password = 
                    new PasswordDeriveBytes(palabraPaso, saltValueBytes, 
                        algoritmoEncriptacionHASH, iteraciones);

                byte[] keyBytes = password.GetBytes(tamanoClave / 8);

                RijndaelManaged symmetricKey = new RijndaelManaged();

                symmetricKey.Mode = CipherMode.CBC;

                ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, InitialVectorBytes);

                MemoryStream memoryStream = new MemoryStream(cipherTextBytes);

                CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);

                byte[] plainTextBytes = new byte[cipherTextBytes.Length];

                int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);

                memoryStream.Close();
                cryptoStream.Close();

                string textoDescifradoFinal = Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);

                return textoDescifradoFinal;
            }
            catch
            {
                return null;
            }
        }
    }
}

       private void formIndexarPDF_FormClosed(object sender, FormClosedEventArgs e)
        {
            cifrarAES cifradoAES = new cifrarAES();
 
            proUtilidades.guardarValorConfiguracion("AjpdSoft");
            proUtilidades.guardarValorConfiguracion("BD.Contraseña", 
                cifradoAES.cifrarTextoAES (txtContrasena.Text, "AjpdSoft_Frase_Encriptado", 
                    "AjpdSoft_Frase_Encriptado", "MD5", 22, "1234567891234567", 128));
        }

        private void formIndexarPDF_Load(object sender, EventArgs e)
        {                    
            cifrarAES cifradoAES = new cifrarAES();

            txtUsuario.Text = "AjpdSoft";
            txtContrasena.Text =
                cifradoAES.descifrarTextoAES(txtContrasena.Text, "AjpdSoft_Frase_Encriptado", 
                     "AjpdSoft_Frase_Encriptado", "MD5", 22, "1234567891234567", 128);
        }

Publicado el: 2012-07-11