# SEAIS: Secure and Efficient Agricultural Image Storage Combining Blockchain and Satellite Networks
## 6 Experimental Evaluation  
In this section, a simulation experiment is provided concerning the processing and storage of agricultural images from satellite networks. The experiment is conducted on Hyperledger Fabric for blockchain storage and NS-3 for network simulation, deployed in a virtual machine with an AMD EPYC 7713 CPU @4.0 GHz, 8 GB RAM, and 40 GB of storage. We use open-source Sentinel-2 satellite images, obtained from the Copernicus Open Access Hub ([[https://scihub.copernicus.eu/](https://scihub.copernicus.eu/)]([https://scihub.copernicus.eu/](https://scihub.copernicus.eu/))) (accessed on 8 July 2024) [34], for encryption and decryption analysis. Sentinel-2 provides images for a wide range of agricultural applications, making it particularly relevant to the proposed scheme. The image transmission times were tested under various network conditions simulated in the NS-3 environment, including scenarios representing remote or extreme environments. This helped assess the robustness and performance of the proposed scheme under challenging conditions. We utilized images with pixels of \((128\times 128)\), \((256\times 256)\), \((512\times 512)\), and \((1024\times 1024)\). The dataset consisted of 50 images from Sentinel-2, with sizes ranging from 10 MB to 100 MB, depending on the image resolution and spectral bands used. Note that the final experimental data is the average of 50 experiments carried out. We first text image encryption and decryption time based on satellite networks using the dataset from Copernicus Open Access Hub, analyzing the impact of independent variables, namely image size and quantity, on the time overhead for image encryption and decryption. In the experiment, we set the image sizes ranging from \((128\times 128)\) to \((1024\times 1024)\). In addition, the encryption algorithm used is the Paillier homomorphic encryption with a key length of 2048 bits to ensure adequate security. The bit error rate (BER) is set to \(1\times 10^{-5}\), simulating typical transmission errors in satellite communications. For comparative analysis, we also evaluated the performance of the scheme proposed by [PERSON] et al. [35], which used a similar homomorphic encryption approach. As shown in Figure 1(a), the average encryption and decryption rates remain stable, regardless of the image size. However, as the image size increases, the encryption and decryption times gradually increase. The encryption and decryption times for \((1024\times 1024)\) image are 63.95 times and 63.69 times those for the \((128\times 128)\) image, respectively. Compared with the scheme proposed by [PERSON] et al., our system shows better scalability, especially with larger image sizes. For the \((1024\times 1024)\) image, encryption time of SEAIS is 1417.8 s compared to [PERSON]'s 1500 s, and the decryption time is 424 s versus 460 s. As shown in Figure 1(b), we fix the image size to \((256\times 256)\) because the throughput rate remains stable, and the time overhead grows linearly with the increase in the number of image blocks. Additionally, our system maintains higher throughput rates, especially for decryption. The strength of SEAIS is its ability to scale efficiently with larger datasets,maintaining stable time overhead and throughput, unlike the comparison approach, which experiences higher overhead and reduced throughput as data size increases. Moreover, we then simulate the image transmission time overhead in a data transmission model using the NS-3 environment. The communication rate is set to 50 Mbps to reflect typical satellite network bandwidth, which is generally lower than ground networks due to distance and cost constraints. The channel delay of 800 ms simulates the high latency common in satellite communications, reflecting the propagation delay over large distances. A signal-to-noise ratio (SNR) of 15.0 is chosen to represent moderate noise levels, simulating interference from environmental conditions and long transmission distances. The channel capacity is around 100 Mbps to 150 Mbps.