Concepts

The building blocks atcomm stands on. All are open standards, and nothing here is owned by atcomm.

atproto (the AT Protocol)

An open protocol for social applications. It gives each person a portable identity (a stable identifier called a DID, e.g. did:plc:…, reachable by a human-readable handle) and a personal data repository (a PDS) they control, independent of any single app. atcomm uses that identity as your messaging identity, and stores a small record in your PDS that points to your messaging key.

DIDComm

An open standard for private, secure messaging between DIDs. A message is encrypted to the recipient's keys and can be relayed by intermediaries called mediators: mailbox servers that hold and forward messages without being able to read them. atcomm uses DIDComm v2.

End-to-end encryption (E2EE)

Only the people in a conversation can read its messages. Every server in between carries ciphertext it cannot decrypt. This is stronger than ordinary transport encryption (the lock icon / TLS), where the connection is encrypted but the server at the other end can still read your messages. With E2EE, the infrastructure never holds the keys.

Put together: your atproto identity says who you are, DIDComm carries the messages, and end-to-end encryption keeps them readable only by you and the person you're talking to. See how it works for the flow, or the spec for the details.