On introducing noise into the bus-contention channel
James W. Gray · 2002
We explore two approaches to introducing noise into the buscontention channel: an existing approach called fuzzy time, and a novel approach called probabilistic partitioning.We compare the two approaches in terms of the impact on covert channel capacity, the impact on performance, the amount of random data needed, and their suitability for various applications.For probabilistic partitioning, we obtain a precise tradeoff between covert channel capacity and performance.'Actually, this discussion is slightly simplified froin Hu's work.To address all types of clocks, Hu introduces "upticks" (which are used for notification of incoming events) and "downticks" (which are used for notification of outgoing events).However, for the present discussion it is sufficient to consider a single fuzzy reference clock.VAX is a trademark of Digital Equipment Corporation.