public static PgpSecretKey ImportSecretKey(this Stream secretIn)
        {
            var secRings =
                new PgpSecretKeyRingBundle(PgpUtilities.GetDecoderStream(secretIn)).GetKeyRings().OfType <PgpSecretKeyRing>();
            var secKeys = secRings.SelectMany(x => x.GetSecretKeys().OfType <PgpSecretKey>());
            var secKey  = secKeys.FirstOrDefault();

            return(secKey);
        }