Fully Secure Lightweight Certificateless Signature Scheme for IIoT

In recent years, Industrial Internet of Things (IIoT) has become increasingly important for applications in the industry. Inevitably, security for IIoT has become a priority in order to deploy secure applications. Amongst available cryptographic tools, certificateless signature schemes offer sound authentication solutions and avoid public-key certification from Trusted Third Parties (TTP). Certificateless signatures solve the key escrow problem against the dishonest Private Key Generator (PKG) and has considered to be a useful tool for IIoT applications. Recently, Karati et al. (IEEE Trans. Industrial Informatics, vol.14, no. 8, 2018) presented a lightweight certificateless signature scheme for IIoT Environments. This scheme was then broken by Zhang et al. (IEEE Access, vol. 8, 2018) by simply allowing to change the public key of the signer and using the homomorphic property of the original scheme. In this paper, we introduce a new attack to the scheme against the existential unforgeability, which is universal since we do not have to assume homomorphic property. We then introduce an entirely new lightweight certificateless signature scheme, which has been proven to be fully secure against all attacks found earlier. Our scheme is the first lightweight certificateless signature scheme with full security and is the most efficient in comparison with other existing schemes. It is desirable for IIoT applications. We also provide experimental results to justify our claims.