[Wee22] Optimal Broadcast Encryption and CP-ABE from Evasive Lattice Assumptions

Authors: Hoeteck Wee | Venue: EUROCRYPT 2022 | Source

Abstract

We present new constructions of broadcast encryption and ciphertext-policy attribute-based encryption (CP-ABE) for ${\mathsf{NC}}^1$ circuits with optimal parameters — $O(1)$ ciphertext overhead and $O(1)$ public key size — from a new lattice assumption called evasive LWE. Evasive LWE posits that a standard LWE instance remains indistinguishable from uniform even when the adversary is given a trapdoor for a matrix derived from the LWE matrix. The assumption is motivated by the structure of the constructions and is incomparable to standard LWE; it evades known lattice attacks because the trapdoor does not directly help invert the LWE problem.