To address the problems of centralized attribute authority, inefficient encryption and invalid access control strategy in the data sharing scheme based on attribute-based encryption technology, a smart grid data sharing scheme that supports policy update and traceability is proposed. The smart contract of the blockchain is used to generate the user’s key, which does not require a centralized attribute authority. Combined with attribute-based encryption and symmetric encryption technology, the confidentiality of smart grid data is protected and flexible data access control is achieved. In addition, online/offline encryption and outsourced computing technologies complete most of the computing tasks in the offline stage or cloud server, which greatly reduces the computing burden of data owners and data access users. By introducing the access control policy update mechanism, the data owner can flexibly modify the key ciphertext stored in the cloud server. Finally, the analysis results show that this scheme can protect the privacy of smart grid data, verify the integrity of smart grid data, resist collusion attacks and track the identity of malicious users who leak private keys, and its efficiency is better than similar data sharing schemes.
The smart grid is a new type of power grid that integrates sensing and measurement technology, communication technology, information technology, computer technology, and control technology with the physical power grid. It can meet customers’ electricity demands and optimize resource allocation, ensuring the safety, reliability, and economy of power supply. With the rapid construction and operation of smart grids, the data generated by various processes such as power generation, transmission, conversion, distribution, consumption and scheduling in the smart grid are exponentially increasing. Cloud computing has powerful computing capabilities and massive storage resources, and more and more power companies are inclined to store grid big data in cloud servers to reduce operating and maintenance costs. However, cloud servers may leak or tamper with the content of grid data for economic or other reasons. The use of encryption technology can ensure the confidentiality of grid data, but traditional “one-to-one” and “many-to-one” encryption algorithms limit the sharing of grid data. Therefore, how to ensure the privacy of grid data while achieving the sharing of smart grid data has become a research hotspot in recent years. Ciphertext policy attribute-based encryption (CP-ABE) allows data owners to choose a set of access control policies to encrypt data, and only users whose attributes satisfy the access control policies can decrypt the data. It is very suitable for smart grid data sharing scenarios. Researchers have proposed a series of cloud-based data sharing schemes based on CP-ABE, which have achieved fine-grained access control of data. In practical applications, user keys depend on attributes, which cannot prevent the risk of malicious users leaking keys. In order to trace the identity of users who leak keys, Liu et al. and Ning et al. designed CP-ABE schemes with traceability function using white-box. Chen et al. proposed a traceable CP-ABE scheme based on fog computing, which binds the user’s identity to the key through a hash function. To reduce the computational burden on access users, some CP-ABE schemes with ciphertext outsourcing decryption computing have been proposed, which outsource a large number of computational tasks to cloud servers or fog nodes. However, most of these schemes require a centralized attribute authority that is absolutely trusted, which is difficult to meet in practical applications.
Blockchain technology has characteristics such as decentralization, immutability, openness, and transparency, which can effectively solve the problems of single points of failure in attribute authority and data silos in the smart grid. The combination of blockchain and CP-ABE technology provides a new approach to designing secure and trustworthy ciphertext data sharing schemes. Zhang et al. proposed a data sharing scheme based on blockchain and CP-ABE, but did not consider the issue of key misuse. Wu et al. applied ABE to blockchain to achieve data privacy protection and fine-grained sharing. Gao et al. proposed a ciphertext access control scheme based on blockchain, but the efficiency is relatively low due to the use of composite order groups. To improve computational efficiency, Hu et al. proposed an attribute-based encryption scheme based on prime-order groups. To verify the integrity of shared data, Fan et al. designed a blockchain-based data sharing scheme, but it cannot effectively resist collusion attacks. However, these schemes do not support access control policy updates and cannot solve problems such as access policy invalidation.
In a dynamic system such as smart grid, the access control strategy needs to be adjusted regularly or irregularly according to factors such as system requirements, changes in the role of participants, and updates in regulations and policies. To enable data owners to modify access control policies, literature proposed data sharing schemes that support policy updates using proxy re-encryption technology. Tian et al. proposed a policy-update CP-ABE scheme based on blockchain, but it does not support identity tracing of malicious users. Das et al. proposed a new ECC-based CP-ABE technology to enable fine-grained access control to data or resources, but does not consider outsourced computation. Guo et al. proposed a cloud data access control scheme that supports policy updates and traceability, but cannot verify the integrity of the data. Based on the CP-ABE scheme in literature, Ge et al. proposed a sharing scheme that supports access policy modification (referred to as Ge scheme hereinafter). However, most schemes only consider the computational performance of decrypting ciphertext by data accessing users, without taking into account the computational cost of encrypting data by data owners. Therefore, they are not suitable for resource-constrained terminal collection devices in the smart grid, such as smart meters. Regarding issues of inaccessible modification of access policies, low encryption efficiency, and potential key abuse, this article proposes an intelligent smart grid data sharing scheme that supports policy updates and traceability. The main work is as follows:
This is the organization of the rest of the paper. In Sect. “Preliminaries”, we show some preliminary knowledge, including bilinear pairing and complexity assumptions. Then, in Sect. “Definition and security models”, the formal definition and system model of the scheme are given. Section “The proposed scheme” explains the specific workflow of the scheme. Section “Security analysis” is the security analysis of the scheme. In Sect. “Performance analysis”, we compare the proposed scheme with the existing schemes. Finally, we provide a summary of the proposed scheme in Sect. “Conclusion”.
