Cwtch (/kʊtʃ/ - a Welsh word roughly translating to “a hug that creates a safe place”) is a decentralized, privacy-preserving, metadata resistant messaging app.
* **Decentralized and Open**: There is no “Cwtch service” or “Cwtch network”. Participants in Cwtch can host their own safe spaces, or lend their infrastructure to others seeking a safe space. The Cwtch protocol is open, and anyone is free to build bots, services and user interfaces and integrate and interact with Cwtch.
* **Privacy Preserving**: All communication in Cwtch is end-to-end encrypted and takes place over Tor v3 onion services.
* **Metadata Resistant**: Cwtch has been designed such that no information is exchanged or available to anyone without their explicit consent, including on-the-wire messages and protocol metadata.
In order to chat with your friends in a peer-to-peer conversation both must be online.
After a successful connection both parties engage in an **authentication protocol** which:
* Asserts that each party has access to the private key associated with their public identity.
* Generates an ephemeral session key used to encrypt all further communication during the session.
This exchange (documented in further detail in [authentication protocol](https://docs.openprivacy.ca/cwtch-security-handbook/authentication_protocol.html)) is *offline deniable*
i.e. it is possible for any party to forge transcripts of this protocol exchange after the fact, and as such - after the
fact - it is impossible to definitely prove that the exchange happened at all.
One the authentication process is successful then both you and your friend can communicate away assured that no one else
can learn anything about the contents or the metadata if your conversation.
## Offline Delivery via Untrusted Routing Servers, and Group Conversations
**Note: Metadata Resistant Group Communication is still an active research area and what is documented here
