Provably Secure Key Assignment Schemes from Factoring

Eduarda S. V. Freire and Kenneth G. Paterson


We provide constructions for key assignment schemes that are provably secure under the factoring assumption in the standard model. Our first construction is for simple chain hierarchies, and achieves security against key recovery attacks with a tight reduction from the problem of factoring integers of a special form. Our second construction applies for general hierarchies, achieves the stronger notion of key indistinguishability, and has security based on the hardness of factoring Blum integers. We compare our constructions to previous schemes, in terms of security and efficiency.

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