Overview of Secure Time Synchronization in NTP

This paper provides an overview of the fundamental principles, historical evolution, and current security challenges of the Network Time Protocol (NTP), along with a detailed exploration of various enhancement methods proposed to address existing vulnerabilities. Initially, the paper analyzes the working mechanisms of NTP and its version progression, highlighting the protocol's critical role in ensuring consistent time synchronization and event ordering within distributed systems. Subsequently, it delves deeply into typical security threats faced by NTP, including packet spoofing, replay attacks, Denial of Service (DoS) attacks, as well as vulnerabilities inherent in the protocol's implementation. Moreover, the paper summarizes multiple security enhancement approaches proposed by researchers globally in recent years, including the Autokey protocol featuring authentication and key exchange mechanisms, authentication models leveraging Elliptic Curve Digital Signature Algorithm (ECDSA) and Secure Sockets Layer (SSL) certificates, the standardized Network Time Security (NTS) protocol, and security enhancement techniques integrating Chinese cryptographic standards and digest authentication mechanisms. Additionally, the paper highlights the shortcomings of existing approaches in practical application scenarios, particularly emphasizing the insufficient security research on the broadcast mode of NTP. It further points out the necessity of systematic design and verification of security strategies related to broadcast mode, aiming to meet synchronization security requirements across broader and more complex network environments.