Fault-tolerant Non-interference

This paper is about ensuring security in unreliable systems. We studysystems which are subject to transient faults – soft errors that cause stored valuesto be corrupted. The classic problem of fault tolerance is to modify a system sothat it works despite a limited number of faults. We introduce a novel variantof this problem. Instead of demanding that the system works despite faults, wesimply require that it remains secure: wrong answers may be given but secretswill not be revealed. We develop a software-based technique to achieve this fault tolerantnon-interference property. The method is defined on a simple assemblylanguage, and guarantees security for any assembly program provided as input.The security property is defined on top of a formal model that encompasses boththe fault-prone machine and the faulty environment. A precise characterization ofthe class of programs for which the method guarantees transparency is provided