End-to-end encryption

Rasum encrypts chats end-to-end. Here you learn what this means, how you can see it in the app and what data the app sends to Rasum.

What does end-to-end encryption mean?

End-to-end encryption means: a message is encrypted on your device and only decrypted again on the recipients’ devices. On the way and on the server, it exists only in encrypted form.

The keys for decrypting are on the devices of the chat participants. The Rasum server only passes on the encrypted messages. It cannot read the content.

iPhone: The chat info shows the note “Message encryption enabled” with the text “Messages are secured with locks. Only you and the recipients have the unique keys to unlock them.”

Are all chats encrypted?

New chats are encrypted. But there can be chats that were created without encryption.

This is how you can tell whether a chat is encrypted:

In an encrypted chat, the message field says “Encrypted message…”, in an unencrypted chat only “Message…”.
iPhone: In an unencrypted chat, the note “Not encrypted” appears above the message field.
Android: The chat info shows a label “Encrypted” or “Not encrypted”.

You open the chat info by tapping the name at the top of the chat.

Turn on encryption for a chat

iPhone: Open the chat info → “Security & privacy” → “Enable end-to-end encryption”. The app asks you to confirm first.

This path is not yet described here for Android.

Which icons show the encryption?

A small icon can appear next to the time of a message. It points to something special about the encryption. Tap the time, and the app explains the icon.

Icon	Looks like	Meaning
	i in a circle	The authenticity of this message cannot be guaranteed on this device.
	question mark in a circle	The message comes from an unknown or unconfirmed device or user.
	crossed-out lock	The message is not encrypted.

All texts and notes are listed under Encryption notes on messages. The icon with the check mark in the header of a direct chat is explained in Confirm your device and identity.

What is the chat backup?

The chat backup is an encrypted backup of your message keys on the server. With it, you can also read older encrypted messages on a new device.

There is no switch to turn off the chat backup. On the iPhone and on Android with a Google account, Rasum sets it up automatically. Without key storage, it is created as soon as you create a key with “Get recovery key”.

The chat backup is unlocked with your recovery key. More about this under Recovery key.

What can Rasum see and what not?

Rasum cannot read the content of encrypted messages. The app says this too: when you report a message, the app points out that the provider cannot read encrypted messages.

Further points:

Notifications: The text of a notification is decrypted on your device. Only a wake-up signal goes through the push service, not the content of your message.
Usage statistics: The app does not send any usage statistics.