The present disclosure provides a secure one-step IEEE 1588 clock using either a symmetric or asymmetric protection scheme. Clocks of mission-critical or highly-available devices in industrial automation systems connected to a communication network are synchronized by sending, by a master clock, a synchronization message, e.g., a single message of the one-step-clock type according to IEEE 1588, including a time stamp, and by receiving and evaluating, by a slave clock, the synchronization message. A synchronization component or module of the master clock prepares, or composes, prior to a projected send time, a synchronization message including a time stamp of the projected send time, and secures the synchronization message in advance of the projected send time. Securing the synchronization message occurs by suitable cryptographic means allowing for authentication of the time stamp at a receiving slave clock. At the projected send time, the secured synchronization message is transmitted.