Information theoretic analysis of side channel information leakage in FCFS schedulers

The information leakage of a queuing side channel in two-user-shared scheduling system is studied from an information theoretic perspective. In the queueing side channel, a malicious attacker can learn the pattern of jobs from a legitimate user using the queuing delays experienced at the shared buffer. An analytical framework is proposed to quantify information leakage using Shannon´s equivocation, and the information leakage of the standard First-come-First-serve scheduler is studied in a slotted system with geometric arrivals. The analysis of the FCFS scheduler demonstrates that the policy provides “good privacy” when arrival rates are very low; the leaked information increases with the rate of the attacker´s jobs and approaches the maximum retrievable information as the sum-rate of arrivals approaches the boundary of the stability region of the queue.