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.
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.