An Incremental Approach to Abstraction-Carrying Code

ion-Carrying Code? Elvira Albert, Puri Arenas, and Germán Puebla 1 Complutense University of Madrid, {elvira,puri}@sip.ucm.es 2 Technical University of Madrid, [email protected] Abstract. Abstraction-Carrying Code (ACC) has recently been proAbstraction-Carrying Code (ACC) has recently been proposed as a framework for Proof-Carrying Code (PCC) in which the code supplier provides a program together with an abstraction (or abstract model of the program) whose validity entails compliance with a predefined safety policy. Existing approaches for PCC are developed under the assumption that the consumer reads and validates the entire program w.r.t. the full certificate at once, in a non incremental way. In the context of ACC, we propose an incremental approach to PCC for the generation of certificates and the checking of untrusted updates of a (trusted) program, i.e., when a producer provides a modified version of a previously validated program. Our proposal is that, if the consumer keeps the original (fixed-point) abstraction, it is possible to provide only the program updates and the incremental certificate (i.e., the difference of abstractions). Furthermore, it is now possible to define an incremental checking algorithm which, given the new updates and its incremental certificate, only re-checks the fixpoint for each procedure affected by the updates and the propagation of the effect of these fixpoint changes. As a consequence, both certificate transmission time and checking time can be reduced significantly.