Intruder deducibility constraints with negation. Decidability and application to secured service compositions
This addresses mediator synthesis for secured services, but it is incremental as it builds on prior work by adding negation handling.
The paper tackles the problem of synthesizing mediators for secured service compositions by extending constraint solving to handle negative deducibility constraints, resulting in a decision procedure implemented in CL-AtSe that applies to subterm convergent theories like encryption and hashing.
The problem of finding a mediator to compose secured services has been reduced in our former work to the problem of solving deducibility constraints similar to those employed for cryptographic protocol analysis. We extend in this paper the mediator synthesis procedure by a construction for expressing that some data is not accessible to the mediator. Then we give a decision procedure for verifying that a mediator satisfying this non-disclosure policy can be effectively synthesized. This procedure has been implemented in CL-AtSe, our protocol analysis tool. The procedure extends constraint solving for cryptographic protocol analysis in a significative way as it is able to handle negative deducibility constraints without restriction. In particular it applies to all subterm convergent theories and therefore covers several interesting theories in formal security analysis including encryption, hashing, signature and pairing.