Message Replay Sample Clauses
Message Replay. Network traffic and valid application layer messages may be captured and resent to OPC clients and servers at a later stage without modification. An attacker could misinform the user or send in improper command such a command to open a valve but at an improper time. Message replay impacts integrity and authorization.
Message Replay. OPC UA uses session ID, timestamps, and sequence numbers for every message request and response. If messages are additionally signed then messages cannot be replayed without detection. Timestamps are specified in the RequestHeader section in [UA Part 4]. Signing is specified in the OpenSecureChannel service in [UA Part 4]. Sequence numbers are specified in the section that specifies the Write, Call, and Notification Message services in [UA Part 4].