On Random-Oracle-Free Top-Level Secure Certificateless Signature Schemes
Certificateless public key cryptography (CL-PKC) overcomes the difficulties of the certificate managements in traditional public key infrastructure (PKI) and the key escrow problem in ID-Based public key cryptography (ID-PKC), concurrently. In 2018, Tseng et al. proposed a certificateless signature (CLS) scheme and claimed that their proposal is the first scheme which satisfies the security against the level-3 KGC (according to Girault's three categorizations of the honesty level of a trusted third party (TTP) which is proposed in 1991), in the standard model. However, we will show that unfortunately their scheme is even vulnerable against a malicious KGC. Afterwards, we will improve their scheme to be robust against the proposed attack. Finally, we will propose a CLS scheme secure against the level-3 KGC in the standard model, based on Yuan and Wang's CLS scheme. We will show that our proposal not only satisfies the level-3 security as well as the basic security requirements of a CLS scheme in the standard model, but also is more efficient than the previous works in the sense of computation and communication costs.
Open Access Status
This publication is not available as open access