# A Blockchain Solution for Remote Sensing Data Management Model
## 3 The Architecture of the System
### Architecture of Remote Sensing Data Sharing Model Based on a Multi-Level Blockchain  
For a single-chain structure in current blockchain-based data management, it is difficult to reach an effective balance between consensus efficiency, security, and cost, and it is not suitable for big data storage. In this paper, we store the original data, data summary, and transaction data separately, study the multi-chain model suitable for remote sensing big data storage, and design multiple chains with a parallel execution, to achieve a high performance as well as a low protection cost, while ensuring data security and privacy security. In this paper, we study the combination method of public and federated chains, further conduct in-depth research on data storage methods in terms of security and performance, focus on the characteristics of remote sensing industry chains, and design a remote sensing blockchain with a high concurrency of transactions. As the storage capacity of a blockchain is limited, and remote sensing data are large, with one datum needing to occupy hundreds of gigabytes of storage space, it is not very realistic to store all remote sensing data on the blockchain, and it could introduce a confidentiality risk. Therefore, in order to provide better on-chain data storage, this paper proposes storing remote sensing data under the chain, and building a data-sharing chain between the remote-sensing-data owners, which stores the hash value of the remote sensing data under the chain for on-chain storage, and ensures the consistency of the hash value of the remote sensing data stored by each remote-sensing-data owner based on the consensus mechanism of blockchain, to realize remote sensing sharing among the remote-sensing-data owners. Combining the characteristics of remote sensing applications, this paper proposes a remote sensing data storage model based on a multi-chain structure combining a public chain and an alliance chain, and designs a three-layer blockchain storage architecture, including an IPFS storage layer, remote sensing industry alliance chain layer, and remote sensing open data public chain layer. Using the IPFS storage layer to store remote sensing raw data and remote sensing product data after processing is convenient for the management and processing of big data, and means that it is not easy to be attacked by others. As remote sensing data are highly specialized compared to general data, in addition to remote sensing image information, they also need to save their descriptive information regarding the remote sensing image data themselves, including spatial, spectral, and temporal dimension information, etc. They need to save metadata information, especially for easy searching. The information hash value is transmitted through the blockchain, and data transmission  
Figure 1: The interoperable meta-information model (own elaboration, based on PROV model [37]). and sharing are realized through IPFS, to achieve secure data sharing. The architecture diagram is shown in Figure 2.  
The remote sensing industry chain needs to perform a parallel cut of data according to the needs of remote sensing application business functions, in order to achieve the business requirements and security requirements of data isolation. As each full node in the single chain in the current blockchain technology system owns all the data in the whole network, it cannot meet such application requirements. This paper designs a 1 + N multi-chain structure based on remote sensing application research, including a public chain and multiple independent alliance chains, which partition business logic and data processing, support the parallel processing of multiple transactions, and asynchronously write to the public chain transaction ledger after the transaction is completed.