Cryptanalysis of Two Privacy-Preserving Authentication Schemes for Smart Healthcare Applications

Abstract

Ensuring the secure sharing of privacy-sensitive healthcare data is attracting considerable interest from researchers. Recently, Ogundoyin et al. designed a lightweight privacy-preserving authentication scheme named PAASH for smart health applications. Benil et al. proposed a public verification and auditing scheme named ECACS for securing e-health systems. Ogundoyin et al. and Benil et al. proposed an efficient certificateless aggregate signature (CLAS) scheme as their respective foundation signature schemes. They declared that their constructions were provably secure under the hardness assumption of cryptographic problems. In this work, we disprove their claim by analyzing the correctness and security of their underlying CLAS schemes. We first show that the batch verification process of n signatures for the CLAS scheme in PAASH is incorrect, and any public-key replacement attacker can easily break the scheme. We analyze the reasons for our attack and propose an improved scheme, named PAASH+. We then show that the CLAS scheme in ECACS fails to achieve correctness, an essential property that a cryptographic scheme should provide. As a result, it is impractical to deploy the designed PAASH and ECACS constructions in any real smart health applications.

A New Conditional Privacy-Preserving Certificateless Aggregate Signature Scheme in the Standard Model for VANETs

“…In 2023, Gong et al [33] proposed a pairing-free PCAS scheme without bilinear pair operations to make the scheme more secure and efficient. This year, Xu et al [34] proposed the PAASH+ scheme that can resist public key substitution attacks to achieve privacy protection in medical scenarios. Li et al [35] also designed a CPPA scheme by introducing linkable group signatures.…”