Success Exponent of Wiretapper: A Tradeoff between Secrecy and Reliability

Equivocation has been widely used as a measure of security after Shannon[10]. For an infinite system such as the wiretap channel defined in [2], equivocation is unbounded and so equivocation rate is used instead. While Maurer et al.[8] point out that the strongest notion of secrecy expressible in terms of equivocation rate is weak in the sense that the wiretapper may learn a fraction of the secret that grows with increasing constraint length n of the system, they also find that strengthening the measure in a way such that wiretapper's knowledge of the secret cannot increase in n results in the same secrecy capacity, which is the maximum data rate at which the secrecy is achieved. In other words, one does not need to sacrifice more data rate for the stronger notion of secrecy, which further supports the use of equivocation rate in general. In [9], however, Merhav et al. use guessing exponent as a measure of security for the Shannon cipher system with a discrete memoryless source. ...

• Type: Journal
• Year: 2008
• Where: CORR
• Authors: Chung Chan
• Keywords: CORR 2008, Education, Equivocation Rate, Secrecy, Strongest Notion