With cloud computing being integrated with wireless body area networks, the digital ecosystem called cloud-assisted WBAN was proposed. In cloud-assisted medical systems, the integrity of the stored data is important. Recently, based on certificateless public key cryptography, He et al. proposed a certificateless public auditing scheme for cloud-assisted WBANs. But He et al. 's scheme is not a scheme with privacy preserving. After many checks on some of the same data blocks, the auditor can derive these data blocks. In this paper, we propose a certificateless public auditing scheme with privacy preserving for cloud-assisted WBANs. In the proof phase of the proposed scheme, the proof information is protected from being directly exposed to the auditor. So, the curious auditor could not derive the data blocks. We also prove that the proposed scheme is secure in the random oracle model under the assumption that the Diffie-Hellman problem is hard, and we give a comparison of the proposed scheme with He et al. 's scheme in terms of security and computation cost.

With the development of Internet, cloud computing has emerged to provide service to data users. But, it is necessary for an auditor on behalf of users to check the integrity of the data stored in the cloud. The cloud server also must ensure the privacy of the data. In a usual public integrity check scheme, the linear combination of data blocks is needed for verification. But, after times of auditing on the same data blocks, based on collected linear combinations, the auditor might derive these blocks. Recently, a number of public auditing schemes with privacy-preserving are proposed. With blinded linear combinations of data blocks, the authors of these schemes believed that the auditor cannot derive any information about the data blocks and claimed that their schemes are provably secure in the random oracle model. In this paper, with detailed security analysis of these schemes, we show that these schemes are vulnerable to an attack from the malicious cloud server who modifies the data blocks and succeeds in forging proof information for data integrity check.

With rapid development of information and communication technologies purchasing digital content through the Internet has been greatly increased. Therefore, secure and fair electronic payment systems are important issue. To reduce system computational, communication and storage costs in many existing electronic schemes, Yang et al. recently proposed a novel electronic payment system based on authenticated encryption technology. But, Chaudhry et al. showed that Yang et al.'s electronic payment system is vulnerable to impersonation attack. Furthermore, Chaudhry et al. proposed improved electronic payment system. But, in this paper we point that Chaudhry et al.'s improved electronic payment system does not satisfy anonymity and fairness properties and the dispute resolution means in Chaudhry et al.'s electronic payment system are not effective. Furthermore, combining authenticated encryption and verifiably encrypted signatures technologies, we propose an improvement on Chaudhry et al.'s electronic payment system. Compared with Chaudhry et al.'s electronic payment system, the major changes of the proposed electronic payment system are in exchange phase. In this phase the private key and public key of the user are not needed, and the user generates verifiably encrypted signatures on his payment voucher. These changes guarantee the user anonymity, eliminate the advantages of the merchant, ensure the fairness of the payment system and the effectiveness of the dispute resolution phase. We also give the comparisons of proposed electronic payment system with some existing electronic payment systems.