An Empirical Analysis of the Nostr Social Network: Decentralization, Availability, and Replication Overhead

Nostr is a decentralized social network launched in 2022, emphasizing high availability and censorship resistance. Since launching, it has gained substantial attention, boasting over 100 million posts. From a user's perspective, it is similar to a micro-blogging service like Twitter. However, the underlying systems infrastructure is very different, and Nostr boasts a range of unique features that set it apart. Nostr introduces the concept of relays, which act as open storage servers that receive, store, and distribute user posts. Each user is uniquely identified by a public key, ensuring authenticity of posts through digital signatures. Users are able to securely replicate and retrieve posts through multiple relays, which frees them from single-server reliance and enhances post availability, thereby attempting to make Nostr censorship resistant. However, this aggressive design also presents challenges, such as the overhead required for extensive post replication and the difficulty in obtaining a global view of post replication locations, which remain unexplored or unaddressed. This necessitates a thorough understanding of the Nostr ecosystem; therefore, we conduct the first large-scale study on this topic. Our study focuses on two key aspects: Nostr relays and post replication strategies. We find that Nostr achieves superior decentralization compared to traditional Fediverse applications. However, relay availability remains a challenge, where financial sustainability (particularly for free-to-use relays) emerges as a contributing factor. We also find that the replication of posts across relays enhances censorship-resistance but introduces significant overhead. To address this, we propose two improvements: one to control the number of post replications, and another to reduce the overhead during post retrieval. Via a data-driven evaluation, we demonstrate their ability to reduce overhead without negatively impacting post availability under the simulated scenarios.