public void roundTripDetached()
        {
            EnvelopedMessage msg = new EnvelopedMessage(true, false);

            msg.AddAttribute(HeaderKeys.Algorithm, AlgorithmValues.AES_GCM_128, true);
            msg.AddAttribute(HeaderKeys.IV, CBORObject.FromObject(rgbIV96), false);
            msg.SetContent(strContent);
            Recipient r = new Recipient(key128, AlgorithmValues.Direct);

            msg.AddRecipient(r);
            msg.Encrypt();

            byte[] content = msg.GetEncryptedContent();

            byte[] rgb = msg.EncodeToBytes();

            msg = (EnvelopedMessage)Message.DecodeFromBytes(rgb);
            msg.SetEncryptedContent(content);
            r = msg.RecipientList[0];
            r.SetKey(key128);
            msg.Decrypt(r);
        }