A sink sends a registration request to a source and the source validates same, and the source sends a registration response including a secret to the sink. The source then sends a proximity message including a nonce to the sink and concurrently notes a start time. The sink employs the secret and the nonce to generate a proximity value and sends same to the sources. The source receives the proximity value and concurrently notes an end time, verifies the proximity value based on the secret and the nonce, calculates from the noted start and end times an elapsed time, compares the elapsed time to a predetermined threshold value, decides from the comparison whether the sink satisfies the proximity requirement, and registers the sink as being able to access content from such source if the sink satisfies the proximity requirement.