# A Blockchain Protocol for Authenticating Space Communications between Satellites Constellations
## 3 Space Digital Tokens (SDT) Concept  
In this section, a new concept called Space Digital Token (SDT) is proposed. The SDT is a way of tokenizing space transactions as digital tokens that can be processed using a blockchain protocol for authenticating space transactions. SDT can be broadcasted within a swarm of satellites network called a satellites constellation. Hence, blockchain can work in this scenario as an authenticator for all communication patterns that can occur within a specific satellite's constellation. SDT can also be used for processing sensing data between satellites and orbital debris, hence, blockchain can works in this scenario as a tracking system for detecting the expected space collisions between satellites and orbital debris. Figure 1 depicts the modeling of space digital tokens using blockchain. It explains how space transactions can be modeled as Space Digital Tokens (SDT) and processed using a blockchain protocol. SDT can be either a transaction exchanged from a satellite to a satellite within a P2P satellite network or maybe in the form of sensing data between a satellite and orbital debris. The blockchain protocol is responsible for verifying the new space transactions to add a new valid block to the blockchain. All space stakeholders would be then able to access the newly added blocks through the connected dashboard to the blockchain platform that manages a satellite constellation.  
The main advantages of tokenizing space transactions as SDT and processing them using blockchain technology can be described as follows:  
1. Better Control of satellite transactions: It would be easier to track, process, validate, and secure all space-related activities when space transactions are tokenized into secure digital tokens. Furthermore, managing and processing them via a smart contract-based blockchain system will facilitate satellite transaction self-verification and execution. Hence, this will lead to a little dependency on the ground stations. In addition, the intended space stakeholders will have better control to allow or deny access to their satellites and spacecraft or share data from or to a satellites network.
2. Faster transactions management: Space transaction management relies heavily on compliance and responsiveness. When it comes to automating different space transaction patterns like satellite-to-satellite (S2S), ground station-to-satellite (G2S), and user- to-satellite (U2S), blockchain could be helpful. Blockchain-based systems would minimize the time taken by a space message to get to the ground station. This could be achieved as the blockchain can, in real-time, manage down/uplink G2S or S2G transactions.
3. Security: Traditional satellite communication systems rely on a single-point-of-access model that introduces significant security issues. Blockchain would help in the decentralization of space networks where space transactions are cryptographically encrypted and tampered-proof. Moreover, blockchain can help space agencies to track and monitor their satellite constellations in a controlled and flexible manner. Thishelp to detect satellite/constellations attacks that seeks to tamper with the satellite software system using space bots [30].