Predictable timestamp under synchronized clocks in a network

In a network-based distributed environment, a timestamp within a message with its life time is generally used to indicate when this message will expire. It is effective using timestamp to prevent message replays, especially in a local environment. We have showed that a predictable timestamp is critical to the security of protocol design because the session key in the protocol may be broken and even imperil the private key. A conclusion has been made that if an encrypted message only contains a timestamp or other predictable data, then its encryption key is easily to be acquired. However, using timestamp can simply indicate the message expiration time, which is very essential to prevent message replays, especially in a local environment. Therefore, we propose adding some unpredictable data with the timestamp in an encrypted message, such as random numbers, for achieving more secure message transmission and authentication protocol