A remote attacker is only able to measure total predetermined latency T = t_work + t_sleep. (Actually, he will measure T + t_noise [network, etc.]). By what me

A remote attacker is only able to measure total predetermined latency T = t_work + t_sleep. (Actually, he will measure T + t_noise [network, etc.]). By what means can he determine which percentage of T+t_noise was spent in actual work?