NTS: Authenticated Time at Meta

• Meta’s public time service now speaks NTS (Network Time Security, RFC 8915) at nts.meta.com. Packets are authenticated, so a device can verify the time came from us and was not modified on the way.
• Our NTS servers hold no per-client state. Cookie keys are derived, not stored and not replicated.
• We’ve open sourced everything, including the protocol, server, client through Meta’s Time library on GitHub.
• We’re also encouraging everyone, particularly those who maintain an NTP client on Android or iOS, to join us in enabling NTS support.

We’ve previously written about building a more accurate time service at Meta scale – migrating from ntpd to chrony, going from 10 milliseconds to 100 microseconds, and opening time.meta.com to everyone.

That work made time precise. This work makes it verifiable.

Why NTS?