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Security & encryption model

AChat promises end-to-end encryption for personal chats, private groups and rooms with a password. It doesn't promise it for communities, their channels, open rooms or status updates.

What end-to-end encryption means here​

  • Messages in those chats can be read only on the devices of the people in them.
  • AChat stores them in a form its servers and administrators can't read.
  • AChat doesn't keep a copy of your message keys, so it can't read or restore your history.
  • Push notifications carry the chat or sender name, never the message text.
  • Search looks only at messages already on your device.

Keys, devices and recovery​

  • Linked devices each hold your keys. Approving a device lets it read your chats, history included, and send messages as you. Compare security codes to check a link.
  • Removing a device stops new messages reaching it and signs it out. What it already stored stays on it.
  • Groups get new keys when their members change, so people who left can't read new messages.
  • The recovery key is yours to keep. Google sign-in alone can't restore your history. Lose the key and every linked device, and nobody can restore it.

Room passwords​

A room with a password encrypts its messages on your device, using that password. Too many wrong tries in a row make you wait before trying again. A password you set gets strength advice checked on your device.

Private location history​

In a personal chat, private group or room with a password, device and location history is encrypted end to end. Only members who enter the chat's audit password (or the room password) can see it, and AChat's administrators can't open it.

What encryption can't do​

  • Anyone who reads a message can copy it. People in a chat can copy, save or screenshot anything, including disappearing and view-once messages while they're open. Deleting later doesn't reach those copies.
  • Open chats are open. Anyone with an open room's link can read it. Communities and their channels aren't end-to-end encrypted.
  • Anonymous isn't untraceable. Your device connects to AChat's servers like any website, and hosts record connection details such as your IP address.
  • A lost, unlocked device is a risk. Whoever holds it can open what's stored there. Privacy on this device covers the privacy screen and Wipe from this device.
  • Nothing already seen can be recalled. A later setting or policy change can't take back what was read, copied, saved or exported.

Moderation and encryption​

AChat's moderators see a message in an encrypted chat only if someone in that chat reports it and sends it with the report. See Admin oversight.