Authenticated Transfer Protocol

The Authenticated Transfer Protocol (AT Protocol or atproto) is a decentralized, federated protocol designed primarily for social media applications. It was developed by Bluesky, a project initially started within Twitter and later spun off as an independent entity. The AT Protocol aims to address issues such as account portability, user privacy, and interoperability across platforms.

Key features of the AT Protocol include:

1. Federation: The protocol enables communication between multiple servers, allowing users to choose their service provider or even self-host their data. This decentralized approach ensures that no single entity controls the entire network.
2. Account Portability: Users can move their accounts, including their data and social graph, between different servers without losing content or connections. This is achieved through the use of decentralized identifiers (DIDs) and signed data repositories.
3. Interoperability: The protocol uses a schema-based framework called Lexicon to standardize communication across different servers, ensuring that applications built on AT Protocol can interact seamlessly with each other.
4. Data Security: User data is stored in cryptographically verifiable repositories, ensuring that it remains secure and tamper-proof. The protocol also uses self-authenticating data to enhance trust and privacy.
5. Algorithmic Choice: Users have control over the algorithms used to curate their social media experience, promoting transparency and user autonomy.

The AT Protocol powers platforms like Bluesky Social and is designed to scale for large-scale use cases while maintaining performance and flexibility for third-party developers.