Lattice-based Signcryption with Equality Test in Standard Model

TL;DR

This paper introduces the first lattice-based signcryption scheme with an equality test in the standard model, enabling secure message confidentiality, authenticity, and equality testing for encrypted data, crucial for cloud computing applications.

Contribution

It presents a novel lattice-based signcryption scheme with equality testing in the standard model, proven secure under standard assumptions, and highlights issues in existing schemes.

Findings

Scheme is secure against insider attacks under LWE and SIS assumptions.

First lattice-based signcryption with equality test in the standard model.

Identifies security flaws in some existing lattice-based signcryptions.

Abstract

A signcryption, which is an integration of a public key encryption and a digital signature, can provide confidentiality and authenticity simultaneously. Additionally, a signcryption associated with equality test allows a third party (e.g., a cloud server) to check whether or not two ciphertexts are encrypted from the same message without knowing the message. This application plays an important role especially in computing on encrypted data. In this paper, we propose the first lattice-based signcryption scheme equipped with a solution to testing the message equality in the standard model. The proposed signcryption scheme is proven to be secure against insider attacks under the learning with errors assumption and the intractability of the short integer solution problem. As a by-product, we also show that some existing lattice-based signcryptions either is insecure or does not work correctly.