Constrained Pseudorandom Functions from Weaker Assumptions
Speaker
Sacha Servan-Schreiber
MIT
Host
Alexandra Henzinger
In this talk, I will present a framework for constructing Constrained Pseudorandom Functions (CPRFs) with inner-product constraint predicates, using ideas from subtractive secret sharing and related-key-attack (RKA) security. I will show three instantiations of the framework:
1. an adaptively-secure construction in the random oracle model;
2. a selectively-secure construction under the DDH assumption; and
3. a selectively-secure construction under the assumption that one-way functions exist.
All three instantiations are constraint-hiding and support inner-product predicates, leading to the first constructions of such expressive CPRFs under each corresponding assumption. Moreover, while the OWF-based construction is primarily of theoretical interest, the random oracle and DDH-based constructions are concretely efficient, which is shown via an implementation.
1. an adaptively-secure construction in the random oracle model;
2. a selectively-secure construction under the DDH assumption; and
3. a selectively-secure construction under the assumption that one-way functions exist.
All three instantiations are constraint-hiding and support inner-product predicates, leading to the first constructions of such expressive CPRFs under each corresponding assumption. Moreover, while the OWF-based construction is primarily of theoretical interest, the random oracle and DDH-based constructions are concretely efficient, which is shown via an implementation.