public byte[] DeriveKey(string password, byte[] salt)
{
var passwordInBytes = PbeParametersGenerator.Pkcs5PasswordToBytes(password.ToCharArray());
var keyGenerator = new Pkcs5S2ParametersGenerator();
keyGenerator.Init(passwordInBytes, salt, _iterations);
var keyParameter = (KeyParameter) keyGenerator.GenerateDerivedMacParameters(_keyBitSize);
var keyBytes = keyParameter.GetKey();
return keyBytes;
}