## 2 Related Work
This effectively solves the problem of single point of failure of the public key infrastructure and provides support for users' fast access authentication. According to latest research results in the field, compared with traditional authentication protocols, the additional overhead brought by blockchain is in an acceptable range, which makes the blockchain technology feasible for LEO satellite networks [23; 24; 25; 26]. Regarding the satellite networks using blockchain technology, [PERSON] et al. proposed a federated learning framework based on blockchain. They quantified the forking probability of the blockchain and exploit double deep Q-network algorithm for efficacious resource allocation [23]. In our protocol, the blockchain we use is consortium blockchain which is one type of the blockchains. Satellite nodes do not compete for bookkeeping rights, so we do not need to consider the bifurcation of blockchain. [PERSON] et al. reviewed some scenarios in which blockchain technology is applied to satellite communication, and discussed the contributions and challenges of deploying blockchain in satellite clusters and the solutions to the challenges [24]. The contribution and challenge of applying blockchain technology to satellite communication have been discussed and its efficacy in satellite communication has been verified. [PERSON] et al. proposed abstracting the characteristics of LEO satellite dynamic topology by using regional division and establishing a consensus among satellites on user authentication by using the consensus mechanism in blockchain. The protocol also combines a distributed hash table and hash lock to reduce storage and computing overhead and to realize user switching authentication in LEO satellite networks [25]. However, it transmits a large amount of data and has a longer communication time. [PERSON] et al. proposed an access authentication protocol combining identity-based encryption and blockchain technology. The protocol can be quickly reconnected to satellites in the same orbit, and two different key management schemes of identity-based encryption and blockchain were studied [26]. However, when users access authenticated satellites in different orbits, complete reauthentication is required. The above work mainly focused on using blockchain to ensure the security of handover authentication by combining the distributed characteristics of satellite networks, but in the initial authentication stage, the correctness of the information added to the blockchain cannot be ensured. Nodes in the same region trust other nodes excessively. Once a malicious node appears in the region, the normal nodes in the same region will not be able to recognize the wrong authentication information. In our protocol, based on the openness and transparency of cryptocurrency, all nodes in the network can verify the correctness of authentication information. As discussed above, centralized secret-key based approaches suffer from single-point-of-failure problem, while blockchain is a distributed method that solves the problem. During the switching authentication process, the satellite can independently authenticate the user identity without communicating with the authentication center, while the traditional protocol cannot. In addition, the blockchain operation has been completed before user switch authentication, which will not affect the performance during the switch authentication process. Moreover, although cryptocurrency is a technology based on blockchain, there is still limited work on cryptocurrencies in LEO satellite networks. Therefore, in this paper, we apply cryptocurrencies to satellite access authentication. The authentication center verifies the user identity and stores a transaction in the blockchain. When a user switches from one satellite to another, the satellite finds the user address included in the transaction within the blockchain.