using System;

using System.Collections.Generic;

using System.Linq;

using System.Security.Cryptography;

using System.Text;

using System.Threading.Tasks;

using System.IO;

​

namespace AppCitasMedac.Shared.Util

{

    public class Encrypter

    {

        // This constant is used to determine the keysize of the encryption algorithm in bits.

        // We divide this by 8 within the code below to get the equivalent number of bytes.

        private const int Keysize = 256;

​

        // This constant determines the number of iterations for the password bytes generation function.

        private const int DerivationIterations = 1000;

        public static void Main() {

            string msg = Decrypt("NsZRcbksjlv/ao/5fHOZUJ12grX/I+wmtFzduTPizm0=", "chattest1");

        }

        public static string Encrypt(string clearText, string encryptionKey)

        {

            byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);

            using (Aes encryptor = Aes.Create())

            {

                Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(encryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });

                encryptor.Key = pdb.GetBytes(32);

                encryptor.IV = pdb.GetBytes(16);

                using (MemoryStream ms = new MemoryStream())

                {

                    using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))

                    {

                        cs.Write(clearBytes, 0, clearBytes.Length);

                        cs.Close();

                    }

                    clearText = Convert.ToBase64String(ms.ToArray());

                }

            }

            return clearText;

        }

​

        public static string Decrypt(string cipherText, string encryptionKey)

        {

            cipherText = cipherText.Replace(" ", "+");

            byte[] cipherBytes = Convert.FromBase64String(cipherText);

            using (Aes encryptor = Aes.Create())

            {

                Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(encryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });

                encryptor.Key = pdb.GetBytes(32);

                encryptor.IV = pdb.GetBytes(16);

                using (MemoryStream ms = new MemoryStream())

                {

                    using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Write))

                    {

                        cs.Write(cipherBytes, 0, cipherBytes.Length);

                        cs.Close();

                    }

                    cipherText = Encoding.Unicode.GetString(ms.ToArray());

                }

            }

            return cipherText;

        }

    }

}

​