RKA Security beyond the Linear Barrier: IBE, Encryption and Signatures

We provide a framework enabling the construction of IBE schemes that are secure under related-key attacks (RKAs). Specific instantiations of the framework yield RKA-secure IBE schemes for sets of related key derivation functions that are non-linear, thus overcoming a current barrier in RKA security. In particular, we obtain IBE schemes that are RKA secure for sets consisting of all affine functions and all polynomial functions of bounded degree. Based on this we obtain the first constructions of RKA-secure schemes for the same sets for the following primitives: CCA-secure public-key encryption, CCA-secure symmetric encryption and Signatures. All our results are in the standard model and hold under reasonable hardness assumptions.