Statistical Selection of Acceptance Time Window to Assure the Freshness of a Protocol Run

Abstract

Timestamps are used to prevent replay attacks in authentication or key distribution protocols; i.e., an authentication message is rejected if the timestamp in the message is judged to be not fresh. Messages that arrive within an acceptance time window are assumed to be legitimate; therefore, we need to choose a proper acceptance time window to mitigate replay attacks while maintaining a high success rate for legitimate authentication requests. This paper discusses the performance of authentication protocols based on intensive simulations with various acceptance time windows and network conditions. Our experimental results show that a secure acceptance time window can be properly selected based on the statistical distribution of the message delay time for legitimate authentication messages.