Paper 2026/2558

Registered ABE via Predicate Encodings, Revisited

Abstract

Predicate encodings, proposed by Wee (TCC'14), are a simple framework that abstracts a variety of attribute-based encryption (ABE) schemes. Zhu et al. showed how to apply predicate encodings to registered ABE (Reg-ABE) using the same definition as in vanilla ABE (Asiacrypt'23). We provide a new definition of predicate encodings that is more suitable for registered ABE and allows us to obtain more efficient Reg-ABE schemes than those by Zhu et al. for predicates captured by predicate encodings. Notably, we obtain \begin{itemize} \item the first Reg-ABE scheme for (non-)zero inner product with $ O(\log L) $-size ciphertexts, \item the first Reg-ABE scheme for conjunctions/disjunctions with $ O(\log L) $-size ciphertexts, \item the first registered broadcast encryption scheme with $ O(\log L) $-size ciphertexts, \end{itemize} under the standard $ k $-Lin assumption, where $ L $ denotes the maximum number of users. Prior to our work, Reg-ABE schemes for (non-)zero inner product, conjunctions, and disjunctions require $ O(\ell\log L) $-size ciphertexts where $ \ell $ is the vector length or the policy size, and registered broadcast encryption schemes rely on the generic group model.