On analyzing the bus-contention channel under fuzzy time

The bus-contention channel is a covert channel that can be exploited at a rate exceeding 1000 bits per second. Fuzzy time is a countermeasure first described by Wei-Ming Hu (1991). To assess the effectiveness of fuzzy time, it is desirable to have an information-theoretic capacity analysis of the bus-contention channel under fuzzy time. The author points out that the capacity of this channel depends on the assumptions that are held regarding the environment in which the channel is being exploited. He discusses various assumptions that may be held regarding the environment. He argues that a capacity analysis under the weakest of these assumptions (viz. the `secure environment assumption) provides an upper bound on the capacity under the other assumptions discussed. It has been argued that a capacity analysis under the stronger assumptions is intractable. Therefore, an analysis under the weaker assumption provides the best available upper bound on the capacity of this channel. The author shows how to analyze the capacity of the channel under the weaker environment assumption and carries out such analysis of the channel using realistic system parameters and variety of fuzzy time parameters