Electronic medical data have significant advantages over paper-based patient records when it comes to storage and retrieval. However, most existing medical data sharing schemes have security risks, such as being prone to data tampering and forgery, and do not support the ability to verify the authenticity of the data source. To solve these problems, we propose a medical data sharing scheme based on attribute cryptosystem and blockchain technology in this paper. First, the encrypted medical data are stored in the cloud, and the storage address and medical-related information are written into the blockchain, which can ensure efficient storage and eliminate the possibility of irreversible modification of the data. Second, the proposed scheme combines attribute-based encryption (ABE) and attribute-based signature (ABS), which achieves the sharing of medical data in many-to-many communications. The ABE achieves data privacy and fine-grained access control, and the ABS verifies the authenticity of the source of the medical data while protecting the signer's identity. Moreover, the data user outsources most of the operations of medical data ciphertext decryption to the cloud service provider (CSP), which can greatly reduce the computational burden. Finally, results of the analysis show that our scheme satisfies the requirements for confidentiality and unforgeability in the random oracle model, and that the proposed scheme offers higher computational performance than other similar schemes. INDEX TERMS Attribute-based cryptosystem, blockchain, confidentiality, electronic medical data, unforgeability.

Cloud storage services provide convenient data storage services for individuals and enterprises. Data owners can remotely access and update outsourcing data. But there are still many security problems, such as data integrity. Although the public audit schemes allow users to authorize third-party auditors (TPA) to verify the integrity of cloud data, there are still a series of problems in the existing public audit schemes. First of all, most of the existing schemes are based on the traditional or identity public key infrastructure. There is a problem of certificate management or key escrow. And they do not support dynamic data update and user identity tracking for group users. Then, existing multi-replica data public audit schemes store all replicas on a cloud storage server. Once the cloud server fails, all replicas will be damaged. Finally, most existing schemes require TPA to be trusted. In practice, TPA may deviate from the public audit protocol or collude with cloud servers to deceive users. To solve these problems, we propose a certificateless multi-replica and multi-cloud data public audit scheme based on blockchain technology. In our scheme, the dynamic hash table and modification record table are introduced to achieve dynamic update of group user data and identity tracking. All replicas are stored in different cloud servers, and their integrity can be audited at the same time. In addition, we use the unpredictability of blocks in the blockchain to construct fair challenge information, thereby preventing malicious TPA and cloud servers from colluding to deceive users. Each audit result is written into the blockchain, which is convenient for users to audit the behavior of TPA. The analysis results show that our proposed scheme is secure in the random oracle model and has higher efficiency in communication and computation cost compared with similar schemes. INDEX TERMS Blockchain, certificateless cryptosystem, cloud storage, data dynamic update, identity tracking, multi-cloud, multi-replica.

With the widespread application of the Internet of Things (IoT), ensuring communication security for IoT devices is of considerable importance. Since IoT data are vulnerable to eavesdropping, tampering, forgery, and other attacks during an open network transmission, the integrity and authenticity of data are fundamental security requirements in the IoT. A certificateless signature (CLS) is a viable solution for providing data integrity, data authenticity, and identity identification in resource-constrained IoT devices. Therefore, designing a secure and efficient CLS scheme for IoT environments has become one of the main objectives of IoT security research. However, the existing CLS schemes rarely focus on strong unforgeability and replay attacks. Herein, we design a novel CLS scheme to protect the integrity and authenticity of IoT data. In addition to satisfying the strong unforgeability requirement, the proposed scheme also resists public key replacement attacks, malicious-but-passive key-generation-centre attacks, and replay attacks. Compared with other related CLS schemes without random oracles, our CLS scheme has a shorter private key, stronger security, and lower communication and computational costs.

No abstract

No abstract