Securing the Precision Time Protocol (PTP) Against Fake Timestamps

Time distribution mechanisms favored for use in the smart grid, such as precision time protocol (PTP), were not designed with security in mind, and thus suffer several security vulnerabilities. PTP is vulnerable to fake timestamp attacks through master impersonation and sync message injection. Such an attack will synchronize clocks to a false time reference. In this letter, we consider an IEC 61850 substation and propose an approach to detect fake timestamps communicated through false PTP sync messages. This approach builds on top of existing network and system management solutions. We introduce a new simple network management protocol data objects to monitor PTP functionality and detect the existence of fake timestamps in a PTP synchronized network. The approach is implemented on a testbed. The collected results demonstrate its ability to protect against fake timestamp attacks.