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Attribute-based encryption (ABE) is a promising management method that enables finegrained access control in large-scale systems. Revocable ABE (RABE) can support a key revocation mechanism in an ABE system. With the advent of the Internet of Things, users may need to delegate their decryption capacity to other devices, which requires that RABE meet a necessary feature called decryption key exposure resistance (DKER). Although many constructions about RABE from bilinear maps have been proposed, the situation of lattice-based constructions with DKER is less satisfactory. In order to narrow this gap, this paper propose the first lattice-based RABE with DKER. First, a formal description of RABE with DKER and the corresponding security models is proposed. Subsequently, a lattice-based RABE scheme without DKER is constructed and it is proved to be selective indistinguishability under chosen-plaintext attack (IND-CPA) security based on Learning with Errors (LWE). To achieve DKER, this paper construct a RABE scheme by using the RABE scheme without DKER and a key extension mechanism as its building blocks. Finally, this paper show that this scheme is selective IND-CPA security, with the DKER based on LWE.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Fully homomorphic encryption (FHE) allows direct computations over the encrypted data without access to the decryption. Hence multi-key FHE is well suitable for secure multiparty computation. Recently, Brakerski et al. (TCC 2019 and EUROCRYPT 2020) utilized additively homomorphic encryption to construct FHE schemes with different properties. Motivated by their work, we are attempting to construct multi-key FHE schemes via additively homomorphic encryption. In this paper, we propose a general framework of constructing multi-key FHE, combining the additively homomorphic encryption with specific multiparty computation protocols constructed from encryption switching protocol. Concretely, every involved party encrypts his plaintexts with an additively homomorphic encryption under his own public key. Then the ciphertexts are evaluated by suitable multiparty computation protocols performed by two cooperative servers without collusion. Furthermore, an instantiation with an ElGamal variant scheme is presented. Performance comparisons show that our multi-key FHE from additively homomorphic encryption is more efficient and practical.

Since hash proof system (HPS) can be utilized to build versatilely cryptographic schemes, the study on realizing this cryptographic primitive has been a very active research area. With the increasing concerns on the huge progress in quantum computing, it urges cryptographers to explore the existence of quantum-resistant HPS schemes, such as the one relying on some lattice-based assumptions. However, most lattice-based HPS proposals are relatively inefficient (e.g., simply outputting one-bit key), even though lattice-based schemes can enjoy many advantageous features: worst-case to average-case reduction, resistance so far to quantum algorithms, and good asymptotic efficiency. Therefore, efficient HPS schemes based on lattice problems are deeply in demand. Through a comprehensive analysis, we found that some lattice-based HPS schemes can be rephrased as their corresponding key encapsulation mechanism (KEM) forms, which generally rely on diverse reconciliation mechanisms and directly imply key exchange protocols under lattice-based assumptions. In this paper, inspired by a novel reconciliation mechanism based on the learning with errors (LWE) problem, we first properly adapt this LWE-based reconciliation mechanism for arbitrary modulus. Then using this improved reconciliation mechanism, we propose an efficient LWE-based HPS scheme which can generate multiple encapsulated key bits and perform better in both computation and storage costs than other related results. Moreover, our proposed lattice-based HPS scheme can be also extended to identity-based and updatable settings for demonstrating its diverse applications.INDEX TERMS Hash proof system, key encapsulation mechanism, key exchange, lattice-based cryptography, learning with errors.