Cryptanalysis of LC-MUME: A Lightweight Certificateless Multi-User Matchmaking Encryption for Mobile Devices

TL;DR

This paper critically analyzes the LC-MUME scheme, revealing security flaws that allow forgery attacks, and proposes modifications to enhance its security for mobile device applications.

Contribution

It provides the first cryptanalysis of LC-MUME, demonstrating its vulnerabilities and suggesting improvements to secure certificateless multi-user encryption schemes.

Findings

LC-MUME fails to achieve EUF-CMA security.

A Type-I adversary can forge ciphertexts without full private keys.

Proposed modifications improve scheme security.

Abstract

Yang et al. proposed a lightweight certificateless multiuser matchmaking encryption (LC-MUME) scheme for mobile devices, published in IEEE Transactions on Information Forensics and Security (TIFS) (DOI: 10.1109/TIFS.2023.3321961). Their construction aims to reduce computational and communication overhead within a one-to-many certificateless cryptographic framework. The authors claim that their scheme satisfies existential unforgeability under chosen-message attacks (EUF-CMA) in the random oracle model. However, our cryptanalytic study demonstrates that the scheme fails to meet this critical security requirement. In particular, we show that a Type-I adversary can successfully forge a valid ciphertext without possessing the complete private key of the sender. Both theoretical analysis and practical implementation confirm that this attack can be mounted with minimal computational cost. To address these weaknesses, we propose a modification strategy to strengthen the security of matchmaking encryption schemes in mobile computing environments.