Paper 2025/807

Registered ABE for Circuits from Evasive Lattice Assumptions

Abstract

Attribute-based encryption (ABE) enables fine-grained access control but traditionally depends on a central authority to issue decryption keys. Key-policy registered ABE removes this trust assumption by letting users generate their own keys and register public keys with an untrusted curator, who aggregates them into a compact master public key for encryption. In this paper, we propose a black-box construction of key-policy registered attribute-based encryption from lattice assumptions in the standard model. Technically, our starting point is the registration-based encryption scheme by Döttling et al. (Eurocrypt, 2023). Building on this foundation, we incorporate the public-coin evasive learning with errors (LWE) assumption and the tensor LWE assumption introduced by Wee (Eurocrypt, 2022) to construct a registered ABE scheme that supports arbitrary bounded-depth circuit policies. Compared to prior private-coin approaches, our scheme is based on more intuitive and transparent security assumptions. Furthermore, the entire construction relies solely on standard lattice-based homomorphic evaluation techniques, without relying on other expensive cryptographic primitives. The scheme also enjoys scalability: the sizes of the master public key, helper decryption key and ciphertext grow polylogarithmically with the number of users. Each user's key pair remains succinct, with both the public and secret keys depending solely on the security parameter and the circuit depth.