ActivityPub API and ActivityPub protocol Evan Prodromou An abstract protocol for E2EE is implemented with the ActivityPub API as the distribution channel. ActivityPub clients do the encryption, decryption, key management, and other E2EE functions. ActivityPub servers provide inter-server distribution of E2EE messages via ActivityPub. Pros 0 A number of high-quality abstract models for E2EE are available ° Seamless integration for end users ° Low or no effort for system administrators ° ActivityPub API is a formal standard with clear IP rights ° ActivityPub API is extremely extensible and flexible, and can handle arbitrary datatypes and properties, giving a close fit for any abstract E2EE protocol and resulting in fewer bugs and security vulnerabilities ° Servers that implement the ActivityPub API have a high likelihood of handling extension properties and datatypes well 0 E2EE may provide an incentive for non-compliant servers to implement the ActivityPub API Cons ° figh effort for client developers ° ActivityPub API is not implemented by Mastodon, durrently the most popular ActivityPub server software ° any otheActivityPal servers do not implement the ActivityPub API