Chrony NTP Authentication Requires Per-Peer Keys and a Rotation Plan

Accurate time underpins certificate validation, log integrity and distributed transactions, and an attacker who can influence an unauthenticated NTP association could shift a host's clock. Chrony supports authenticated time through Network Time Security or symmetric keys, but both require an operational plan. The guidance recommends random keys of at least 128 bits, distinct keys per client-server pair, and restrictive file permissions, with rotation done by adding the new key before removing the old one. Operators are also advised to keep source lists intentional and to treat any fallback to unauthenticated NTP as a documented policy decision. NTS is generally preferred where supported, and monitoring for configuration changes, source changes and clock jumps is recommended.