DarkChan - Private Messenger

DarkChan is an end-to-end encrypted messenger for one community - a family, a group of friends, a club - on a server that one of you runs. There is no DarkChan company in the middle: you type in your server's address, create an account, and the server's administrator approves it.

IMPORTANT: DarkChan does nothing on its own. You need the address of a DarkChan server, run by yourself or by someone you trust. The server software is free to self-host on a small Linux machine, even a Raspberry Pi.

WHAT YOU GET
• One-to-one chats protected by the Double Ratchet: forward secrecy for your private conversations.
• Groups and channels, encrypted for every member, with moderators, invitations and approval to join.
• Photos with previews, a gallery, files of any kind, voice messages and video attachments - all encrypted on your phone before they leave it.
• Emoji and stickers from your community's own packs, updated by the server without an app update.
• Replies, reactions, edits, "delete for everyone", read receipts, typing indicators and presence - each one can be turned off.
• Safety numbers: compare them with a contact to make sure nobody is in the middle. Unverified contacts are clearly marked.
• Several devices per account, and a web portal for when you are not at your phone.
• Message retention ("vanish") you can set per conversation.
• Your data on the phone is encrypted at rest under your password.

PRIVACY, HONESTLY
• The server stores only ciphertext: it cannot read your messages, attachments, file names, thumbnails, link previews, profile pictures or group names.
• The person who runs the server CAN see who talks to whom, when, and how much (sizes and timestamps), and your IP address. Only use a server run by someone you trust.
• No ads, no analytics, no trackers, no crash reporting. The developer runs no server and receives nothing from the app.
• No Google services and no Firebase. Notifications work through the app's own connection or, if you install one, a UnifiedPush distributor such as ntfy, which carries a content-free wake-up only. Messages are decrypted on your phone and the notification is written there.
• Link previews are made by the sender, never by the server; you can turn them off.
• You can delete your account from the app (Settings → Delete my account) or from the server's web portal.

NOTIFICATIONS ON ANDROID
To deliver messages while the app is in the background, DarkChan keeps its encrypted connection open in a foreground service with a small, silent "Connected" notification. Some phones (Xiaomi, Huawei, Oppo...) stop background apps anyway: the Settings screen shows whether delivery is healthy and when the last sync happened, and points you to the right setting.

FOR THE SERVER ADMINISTRATOR
The server is a single Linux program (Debian packages, Docker or from source) with flat-file storage, TLS 1.3, account approval, roles and moderation, rate limits, backups and a browser portal. It is designed for up to about 200 users.

DarkChan's cryptography uses standard, well-studied building blocks from OpenSSL (X25519, Ed25519, ChaCha20-Poly1305, HKDF, scrypt). It has not been independently audited.

Recent changes:
• A device you add to your account now shows what you write on your other devices straight away, even in private chats nobody has written in since
• In a private chat that began before a device was added, that device can write as soon as the other person's app is online
• If a message cannot reach the other person yet, the app says so and keeps your text