# A Blockchain Solution for Remote Sensing Data Management Model
## 2 Problem Description
### Research on Data Storage Architecture of Blockchains  
Compared with traditional databases, a blockchain also has many shortcomings in terms of performance. In terms of data storage, as all nodes in a blockchain system keep a copy of the blockchain, the increasing growth in data makes storage more and more difficult. To address this problem, researchers have proposed several expansion schemes, such as modifying the block capacity [21], converting the originally single-chain data structure to a directed acyclic graph (DAG) [22], or shifting complex computations and high-frequency transactions to be performed off-chain, and storing the final results on the blockchain. The modifications in block capacity and directed acyclic graphs are mainly improved from the blockchain architecture, to enhance the whole network's transaction processing capacity. However, this approach is mostly limited by the number of nodes and transactions in the network, with limited performance improvement, and it tends to exacerbate the risks of blockchain centralization and security attacks. One solution is to move computation and high-frequency transactions off-chain. This solution separates off-chain computation from on-chain storage. It can effectively improve blockchain performance, while guaranteeing a certain degree of decentralization. However, off-chain scaling faces problems, such as off-chain computation security and difficulty in supporting complex operations (e.g., smart contracts). Therefore, in-depth research on decentralization, security, and performance needs to be conducted in a specific study concerning the characteristics of remote sensing data and applications. The traditional blockchain represented by Bitcoin introduces a single-layer chain structure in terms of blocks, which is used to guarantee the tamper-evident nature of data on the chain. The block header and the block body, together, constitute a complete block. The block header stores the antecedent parent block hash, the transaction set Merkle root, etc., and the transaction data are stored in the block body. Currently, most blockchain systems are using single-chain architecture, such as the PoC project of the Japanese network bank, and the common ledger model of the European Central Bank. With the increase in data stored on the blockchain, research has found that the single-chain architecture has corresponding bottlenecks, in terms of performance, capacity, privacy, and scalability, which are insufficient to manage the data, and a double-chain structure blockchain was invented, inspired by the DNA structure. The double-chain structure blockchain means that two chains can compute in parallel, and each chain can use different hardware; the double-chain structure not only maintains the characteristics of the original blockchain, but also improves the computing speed and scalability. In domestic and international research, according to the needs of each application, scholars have proposed their double-chain structure. To solve the characteristics of the single-chain structure without supervision and legal protection [23], [PERSON] et al. [24] proposed a double-chain structure of a supervisory blockchain and transaction blockchain, to separate supervision and transaction. [PERSON] et al. [25] proposed a dual-chain structure of a transaction blockchain and data blockchain for the blockchain-based tracking of agricultural products, which solved the security problem and ensured that the data would not be maliciously tampered with or destroyed. [PERSON] et al. [26] used a combination of an ETH public chain and an agricultural sample data chain to improve the security level. [PERSON] et al. [27] proposed a user blockchain and fog aggregation blockchain, again to enhance security. To alleviate the block data storage inflation problem, [PERSON] et al. [28] established a double-chain structure of main and summary chains, which allows users to choose the appropriate storage mode according to their needs, which is also a more mainstream double-chain structure.