Bluesky Social Bluesky Social This document specifies the repository and synchronization semantics for Authenticated Transfer (AT), a protocol for cryptographically- verifiable storage and distribution of structured user-controlled data. It defines the AT repository that serves as the fundamental data storage model. It further specifies synchronization mechanisms that allow efficient distribution of repository changes to interested parties. This document specifically deals with the repository and sync protocol. Overall network architecture is described further in [AT-ARCH].