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July 2005

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2005-14: Code Stabilization
by Volker Stolz 05 Jul '05

05 Jul '05

The following technical report is available from http://aib.informatik.rwth-aachen.de/: Code Stabilization Felix C. Freiling, Sukumar Ghosh AIB 2005-14 Dijkstra's concept of self-stabilization assumes that faults can only affect the variables of a program. We study the notion of self-stabilization if faults can also affect (i.e., augment) the program code of a system. A code stabilizing system automatically recovers from (almost) arbitrary perturbations of its program code. We prove some lower bounds for code stabilizing systems and argue that code stabilization has many resemblances to the area of integrity management in the domain of security.

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2005-13: Revisiting Failure Detection and Consensus in Omission Failure Environments
by Volker Stolz 05 Jul '05

05 Jul '05

The following technical report is available from http://aib.informatik.rwth-aachen.de/: Revisiting Failure Detection and Consensus in Omission Failure Environments Carole Delporte-Gallet, Hugues Fauconnier, Felix C. Freiling AIB 2005-13 It has recently been shown that fair exchange, a security problem in distributed systems, can be reduced to a fault tolerance problem, namely a special form of distributed consensus. The reduction uses the concept of security modules which reduce the type and nature of adversarial behavior to two standard fault-assumptions: message omission and process crash. In this paper, we investigate the feasibility of solving consensus in asynchronous systems in which crash and message omission faults may occur. Due to the impossibility result of consensus in such systems, following the lines of unreliable failure detectors of Chandra and Toueg, we add to the system a distributed device that gives information about the failure of other processes. Then we give an algorithm using this device to solve the consensus problem. Finally, we show how to implement such a device in an asynchronous system using some weak timing assumptions.

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