  Due to the increasing dependency of critical infrastructure on synchronized
clocks, network time synchronization protocols have become an attractive target
for attackers. We identify data origin authentication as the key security
objective and suggest to employ recently proposed high-performance digital
signature schemes (Ed25519 and MQQ-SIG)) as foundation of a novel set of
security measures to secure multicast time synchronization. We conduct
experiments to verify the computational and communication efficiency for using
these signatures in the standard time synchronization protocols NTP and PTP. We
propose additional security measures to prevent replay attacks and to mitigate
delay attacks. Our proposed solutions cover 1-step mode for NTP and PTP and we
extend our security measures specifically to 2-step mode (PTP) and show that
they have no impact on time synchronization's precision.
