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Encryption you can explain
Messages are encrypted on your device and only become readable again on the recipient’s device. Here’s how it works – and where the limits are.
A message’s journey
From device to device
- The key is created on the deviceOn first start, every phone, every PC and every browser generates its own key pair. The private part stays on the device.
- The public key is storedOnly the public part goes to the server, so that others can send you encrypted messages.
- Encrypted before sendingYour message is encrypted separately for each of the recipient’s devices – and as a copy for your own other devices.
- The server only deliversIt stores and distributes chat messages only as ciphertext. It can’t read them.
- Decrypted by the recipientOnly the target device can open the message with its private key.
Technology
The building blocks in detail
Android, Windows and the browser use the same method. The browser version was tested against the Android library so that all devices can read each other’s messages.
- Messages: HPKE per RFC 9180, compatible with Google Tink
- Photos, videos, voice messages and files: a random 256-bit key per file (AES-256-GCM). This key itself travels encrypted inside the message.
- What an account may read in the database is governed by row permissions (Row Level Security).
- Connections to the server use HTTPS.
KDF HKDF-SHA256
AEAD AES-128-GCM
Mode HPKE Base · Tink-Format
Files AES-256-GCM · key per file
Keys per device, stays on the device
HPKE (Hybrid Public Key Encryption) is an open IETF standard.
On every device
Protection you set yourself
App lock
Four-digit PIN, optionally fingerprint or face. Off by default.
Self-deleting messages
After one hour, one day, seven days, one month or 90 days – for all chats or just one.
View once
Photos and videos that delete themselves after viewing. The Android and Windows apps block screenshots of them.
Delete old media
Remove received photos, videos and voice messages from the device after a set period; the text stays.
Visibility
You decide whether others can find you in the user directory – or only people who know your exact username.
Verified updates
The Windows app only installs updates with a valid digital signature.
Being upfront
What end-to-end encryption doesn’t cover
Security also means knowing the limits. These areas have a different kind of protection:
Calls and live streams
They are encrypted in transit (WebRTC with DTLS-SRTP) and run via the messenger’s own server.
Emails
Email works as it does with any email provider. Emails are not end-to-end encrypted – not even between two @messenger-mail.de addresses.
Calendar, notes and lists
They are stored encrypted (AES-256-GCM), but with an app key rather than your device key.
Telegram, Signal and WhatsApp
The bridge on the messenger’s own server decrypts these messages and re-encrypts them for your devices. They are not end-to-end between you and the person you’re chatting with.
Translation and speech recognition
If you turn on automatic translation, the messenger’s own server sends the text to DeepL for translation. Spoken commands are recognised by the phone or the browser – in the browser, for example, via Google or Apple.
New device
A newly signed-in device can’t read messages that arrived before it signed in – except via a restored backup. If the website data is cleared in the browser, it counts as a new device.
Status and stream chat
Status photos and videos are stored encrypted on the server – but so is their key. Captions and stream chat are not encrypted.