Secure Network Time Protocol
Protocol stime-ntpauth (62), defined in [120], uses public-key cryptography for the Network Time Protocol Version 2, which is used to securely obtain time from authenticated sources. Secure Network Time is becoming a key factor in security and non-repudiation. Existing approaches to distributing time are vulnerable to external attack and tampering, as these do not take advantage of advances in public key infrastructure and cryptographic methods, and require distribution of cryptographic keys via non-scalable out-of-band means. Securing time distribution using PKI mechanisms allows the process to scale and minimizes risk.
Protocol TSP (63), the Time-Stamp Protocol, defined in [9] (Internet X.509 Public Key Infrastructure Time-Stamp Protocol, TSP) is in the expanded scope of the IETF PKIX Working Group.
Protocol stime-ntpauth and Protocol TSP should provide Authentication and Replay Protection (G1,2,3).