The influence of delay upon an idealized channel's bandwidth

An optimization problem in calculating the bandwidth of a covert timing channel is discussed. In particular, the question of how dependent the bandwidth is on the magnitude of the modulation is addressed. A generalization of that covert channel is presented and its bandwidth (capacity) is studied. Attention is given to how the delay that HIGH uses to signal LOW affects the bandwidth. Increasing the delay lessens the noise but increases the time required to pass a symbol along the channel. What the optimal delay should be and how it influences the security of the system was studied. Because of the complicated nature of the formulas involved, closed-form solutions for some of the terms of interest cannot be given. Instead, numerical techniques and plotted results are used.<<ETX>>

[1]  Ira S. Moskowitz,et al.  Variable noise effects upon a simple timing channel , 1991, Proceedings. 1991 IEEE Computer Society Symposium on Research in Security and Privacy.

[2]  Harry Hochstadt,et al.  The functions of mathematical physics , 1972 .

[3]  A. W. Kemp,et al.  A treatise on generating functions , 1984 .

[4]  Wei-Ming Hu,et al.  Reducing timing channels with fuzzy time , 1991, Proceedings. 1991 IEEE Computer Society Symposium on Research in Security and Privacy.

[5]  Claude E. Shannon,et al.  The Mathematical Theory of Communication , 1950 .

[6]  John C. Wray,et al.  An analysis of covert timing channels , 1991, Proceedings. 1991 IEEE Computer Society Symposium on Research in Security and Privacy.

[7]  Sergio Verdú,et al.  On channel capacity per unit cost , 1990, IEEE Trans. Inf. Theory.

[8]  D. Elliott Bell,et al.  Secure Computer System: Unified Exposition and Multics Interpretation , 1976 .

[9]  Ira S. Moskowitz,et al.  The channel capacity of a certain noisy timing channel , 1992, IEEE Trans. Inf. Theory.

[10]  Solomon W. Golomb,et al.  The limiting behavior of the Z-channel (Corresp.) , 1980, IEEE Trans. Inf. Theory.

[11]  Jonathan K. Millen Finite-state noiseless covert channels , 1989, Proceedings of the Computer Security Foundations Workshop II,.

[12]  Peter J. Denning,et al.  Operating Systems Theory , 1973 .

[13]  Ira S. Moskowitz Noise Effects Upon a Simple Timing Channel , 1990 .

[14]  Daryl McCullough,et al.  Covert Channels and Degrees of Insecurity , 1988, CSFW.