A trusted content usage monitor for monitoring content usage is provided. A unique identifier generation unit generates a unique identifier indicative of content being rendered and a packet generator generates a trusted packet comprising the unique identifier. The trusted packet is trust signed by the trusted content usage monitor, so that it can be trusted by its recipient. The trusted content usage monitor has at least one mode of operation in which content rendering cannot be decoupled from operation of the unique identifier generation unit, so that generated packets can be trusted as truly indicative of content usage.