The ISC International Journal of Information Security

Abstract Wireless Body Area Networks (WBANs) have attracted a lot of attention in recent researches as they play a vital role in diagnosing, controlling and treating diseases. These networks can improve the quality of medical services by following the health status of people and providing online medical advice for them, momentarily. Despite the numerous advantages of these networks, they may cause irrecoverable problems for patients, if security considerations are not properly met. So, it is very important to find solutions for satisfying security requirements in these networks. A signcryption scheme can be considered as one of the most important cryptographic tools for providing the security requirements in WBANs. Recently, Kasyoka et al. proposed a signcryption scheme based on which they designed an access control protocol for WBANs. They proved the security of their proposals in the random oracle model (ROM). In this paper, we concentrate on Kasyoka et al.’s proposals and show that their proposed signcryption scheme and consequently their proposed access control protocol for WBANs are vulnerable against various attacks, in contrast to their claims. Afterward, we fix the scheme to be secure against our proposed attacks.

Abstract The certificateless public key cryptography (CL-PKC) setting, makes it possible to overcome the problems of the conventional public key infrastructure and the ID-Based public key cryptography, concurrently. A certificateless signcryption (CL-SC) scheme is an important cryptographic primitive which provides the goals of a signature scheme and an encryption scheme both at once, in a certificateless setting. In addition to the basic security requirements of a CL-SC scheme (i. e. the unforgeability and the confidentiality), a new security notion called as the known session specific temporary information security (KSSTIS) has been proposed in the literature, recently. This security notion guarantees the confidentiality of the message even if the temporary information, used for creating the signcryption on the message, reveals. However, as discussed in the literature, there are not any secure CL-SC schemes in the standard model (i. e. without the assumption of random oracles) which guarantees the KSSTIS. In this paper, three recently proposed CL-SC schemes (Caixue, Shan and Ullah et al.'s schemes) are analyzed and it is shown that these schemes not only do not satisfy the KSSTIS, but also they do not even provide the basic security requirements of a CL-SC scheme. Furthermore, an enhanced secure CL-SC scheme is proposed in the standard model which satisfies the KSSTIS.