Privacy preserving detection of patterns in event sequences

We propose to use pattern matching on data streams from sensors in order to monitor and detect events of interest. We consider a privacy preserving pattern matching problem where patterns are given as sequences of constraints on input elements. We describe a new privacy preserving pattern matching algorithm over an injinite al h,,.abpet A where a pattern P is given as a sequence {pi(1), pi(2) ,..., pi(m)} of predicates pi(j) defined on A. The algorithm address the following problem: given a pattern P and an input sequence t, find privately all positions in t where P matches t. The privacy preserving in the context of this paper means that sensor measurements will be evaluated as predicates p(i) (e(j)) privately, that is, sensors will not need to disclose the measurements x(i)((j)), x(2)((j)) ,..., x(n)((j)) to the evaluator.