## 1 Introduction  
In the era of information explosion, big spatio-temporal data have become an important branch in the field of data science. Big spatio-temporal data refer to those large datasets that possess temporal and spatial attributes. This type of data are usually captured or generated at specific times and locations and can provide detailed information about the timing and geographical position of objects or events. As mobile internet and IoT technologies rapidly advance, the Internet of Things (IoT) and big data technologies, especially the widespread application of the Global Positioning System (GPS), generate a vast amount of data labeled with time and geographical information. These datasets are not only large but also update rapidly. Big spatio-temporal data not only demand greater storage capacity but also pose unprecedented challenges to data security and privacy protection [1]. At present, although cloud storage provides a solution for the massive volumes of big spatio-temporal data, it also introduces several security issues [2]. Firstly, the separation of data ownership and management makes big spatio-temporal data easily accessible to unauthorized third parties and even susceptible to tampering and deletion. Secondly, cloud service providers may cause data leakage due to internal vulnerabilities or external attacks, which is particularly critical for big spatio-temporal data that include time and geographical information [3]. Additionally, cloud storage lacks a transparent data deletion mechanism, making it impossible for users to ensure their data are truly and completely removed upon request, thus raising the risk of data misuse or leakage [4; 5]. Consequently, as the volume of big spatio-temporal data increases, traditional data security measures can no longer effectively handle the increasingly complex security threats, urgently requiring new technologies and strategies to ensure the secure management of extensive big spatio-temporal data. Blockchain is a distributed database technology originally designed as the underlying technology for Bitcoin. It allows data to be stored in blocks, which are cryptographically linked together to form a growing chain. Each block contains a series of transaction records, and the data are kept secure and tamper-proof through complex encryption algorithms. The fundamental attributes of blockchain technology encompass decentralization, openness, immutability, and anonymity [6; 7]. After years of development, blockchain technology is not only limited to the initial application of digital currency, but its reach has broadened to encompass diverse fields like financial services, supply chain management, smart contracts, identity verification, and medical record management. It provides new possibilities for solving trust problems, improving efficiency, and reducing costs [8]. Given the exponential rise in big spatio-temporal data, the decentralized nature of blockchain brings advantages in security and transparency but also poses challenges in storage efficiency and scalability [9]. In blockchain, each node must maintain a copy of the entire chain, and with the escalating volume of transactions and data, the data volume of each block also grows. This requires that each participating node have sufficient storage space to maintain the complete blockchain. Therefore, the native design of blockchain is not well-suited for directly handling large-scale, spatio-temporal data. Currently, on-chain storage and off-chain storage are the focus of blockchain scaling technology research. Compared with on-chain storage, off-chain storage significantly improves the scalability of blockchain from the standpoint of storage capacity. By transferring data from on-chain to off-chain storage of blockchain, it not only improves the scalability but also enhances the utilization efficiency of on-chain storage space. However, off-chain storage solutions still face some challenges.