An analysis of the timed Z-channel

Author

Moskowitz, Ira S. ; Greenwald, Steven J. ; Kang, Myong H.

Author_Institution

Centre for High Assurance Comput. Syst., Naval Res. Lab., Washington, DC, USA

Volume

44

Issue

7

fYear

1998

fDate

11/1/1998 12:00:00 AM

Firstpage

3162

Lastpage

3168

Abstract

Golomb analyzed the Z-channel, a memoryless channel with two input symbols and two output symbols, where one of the input symbols is transmitted with noise while the other is transmitted without noise, and the output symbol transmission times are equal. We generalize to the timed Z-channel, where the output symbol transmission times are not equal. The timed Z-channel appears as the basis for a large class of covert (communication) channels appearing in multilevel secure computer systems. We give a detailed mathematical analysis of the timed Z-channel and report a result expressing the capacity of the timed Z-channel as the log of the root of a characteristic equation. This generalizes Shannon´s work on noiseless channels for this special case. We also report a new result bounding the timed Z-channel´s capacity from below. We show how an interesting observation that Golomb reported for the Z-channel also holds for the timed Z-channel

Keywords

channel capacity; computer networks; memoryless systems; processor scheduling; security of data; telecommunication security; CPU scheduling; channel capacity; computer network; covert communication channels; input symbols; mathematical analysis; memoryless channel; multilevel secure computer systems; noise; noiseless channels; output symbol transmission times; output symbols; timed Z-channel analysis; timing channel; Automation; Inspection; Laplace equations; Machine intelligence; Machine vision; Noise shaping; Notice of Violation; Robustness; Shape; Testing;

fLanguage

English

Journal_Title

Information Theory, IEEE Transactions on

Publisher

ieee

ISSN

0018-9448

Type

jour

DOI

10.1109/18.737549

Filename

737549