# A Blockchain Protocol for Authenticating Space Communications between Satellites Constellations
###### Abstract  
Blockchain has found many applications, apart from Bitcoin, in different fields and it has the potential to be very useful in the satellite communications and space industries. Decentralized and secure protocols for processing and manipulating space transactions of satellite swarms in the form of Space Digital Tokens (SDT) can be built using blockchain technology. Tokenizing space transactions using SDTs will open the door to different new blockchain-based solutions for the advancement of constellation-based satellite communications in the space industry. Developing blockchain solutions using smart contracts could be used in securely authenticating various P2P satellite communications and transactions within/between satellite swarms. To manage and secure these transactions, using the proposed SDT concept, this paper suggested a blockchain-based protocol called Proof of Space Transactions (PoST). This protocol was adopted to manage and authenticate the transactions of satellite constellations in a P2P connection. The PoST protocol was prototyped using the Ethereum blockchain and experimented with to evaluate its performance using four metrics: read latency, read throughput, transaction latency, and transaction throughput. The simulation results clarified the efficiency of the proposed PoST protocol in processing and verifying satellite transactions in a short time according to read and transaction latency results. Moreover, the security results showed that the proposed PoST protocol is secure and efficient in verifying satellite transactions according to true positive rate (TPR), true negative rate (TNR), and accuracy metrics. These findings may shape a real attempt to develop a new generation of Blockchain-based satellite constellation systems. blockchain; Proof of Space Transactions (PoST); satellites constellations; satellites communications; satellites authentication +
Footnote †: journal: _Aerospace_  
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create many opportunities such as satellite-as-a-service business models, managing the space supply chain, and even how to build satellite payloads. Moreover, blockchain will make a major transformation in the next generation of financial transactions. Transferring the Bitcoin Blockchain via satellite will make a quantum leap in global financial transactions and grant a robust alternative to terrestrial networks. The Blockstream Satellite network [19] represents a practical application of utilizing blockchain-based satellites for processing and broadcasting the bitcoin to the entire planet without the need for the Internet. For Instance, in 2017, a technical error by Google briefly caused more than half of Japan to lose its connection to the internet. While internet access was returned within the hour, the Japanese faced slow connection speeds, which directly affected financial transactions, and online trading was halted. In this scenario, broadcasting the bitcoin blockchain via satellite would have ensured that the financial transactions are not been halted. Moreover, blockchain remained in sync with the rest of the globe and thus, unaffected by internet disconnect [20]. Moreover, the common characteristics of blockchain technology such as robustness, trust, security, transparency, decentralized connections, and time stamping transactions make it a key technology for managing and securing space communications because it cannot be hacked or centrally controlled. These characteristics make blockchain a qualified technology for providing various services in the space industry [20] such as:  
* _Enhancing the Satellite Value Chain_: Blockchain as a smart contract can be used for launching and operating satellites, accessing transparent information for insurance purposes, and monitoring space operations. Moreover, satellites can also be basic sources of space transactional data for upgrading blocks and verifying the integrity and origin of these data patterns. * _Enabling Cloud Services in Space_: levering both blockchain and AI can enable a cloud transformation and processing in space.