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Guaranteed End-to-End encryption and many other good news
November 23, 2023 by holga
Our rolling 1.42 Delta Chat app releases introduce guaranteed end-to-end encryption, a major security milestone that took many hundreds of hours of challenging work from core Delta Chat teams, experts and collaborators. Friends from activist circles, users and operators of security-related helplines, as well as TeamUSEC all helped us to streamline usability and implementation issues for guaranteed end-to-end encryption.
We’ll first recall two main shortcomings of the Autocrypt end-to-end encryption that Delta Chat is using before describing how 1.42 apps overcome these issues through the universal introduction and refinement of the decentralized SecureJoin protocols, introducing the notion of guaranteed end-to-end encryption which can not be broken by servers or Internet providers.
Oh, and if you don’t care much about encryption, just scroll down to the “other good news” part which may have some exciting news depending on platform for you ;)
There are two frequent criticisms of Delta Chat’s Autocrypt end-to-end encryption and its opportunistic nature:
MITM attack: User’s e-mail servers might try to meddle with the message encryption of their users. Autocrypt Level 1 explicitly does not protect against internet providers or e-mail providers to start MITM attacks against their users. Compromised infrastructure is arguably a stronger concern for Delta Chat than Signal or Whatsapp users. After all, there is a not a single central but many hundreds of different e-mail providers used with Delta Chat today, many of which are operating in surveillance oriented environments or are otherwise exposed to capable adversaries.
Surprises because of unencrypted messages: Users can encounter an irritating lack of end-to-end encryption when they send a first message or if their chat partners don’t consistently use Autocrypt-capable apps. They would send an un-encrypted message and only notice it after they sent a message. In practise, this is less of a problem than many experts think but it still is a valid concern.
Both issues are addressed with the currently rolling out 1.42 Delta Chat app releases as “Guaranteed end-to-end encryption” prevents messages from unexpectedly dropping end-to-end encryption, and protects against compromised servers or networks. While Delta Chat already offered “verified groups” for years, we extended end-to-end encryption guarantees to 1:1 chats and unified group creation along the way: when you create a group with only green-checkmarked contacts, your group chat will automatically get a green-checkmark and introduce guaranteed end-to-end encryption for all chat-members.
Chats marked with a green checkmark guarantee end-to-end encryption: You will only send and receive end-to-end encrypted messages that can not be read or modified by hostile e-mail servers or networks.
To start a guaranteed end-to-end encrypted 1:1 chat, you scan another user’s “QR Invite code” which starts the automatic SecureJoin protocol resulting in a safely end-to-end encrypted chat and a green-checkmarked contact.
If you create a group that only has green-checkmarked contacts then this group will use guaranteed end-to-end encryption that never degrades and can not be broken by e-mail providers or network attackers. Moreover, all members use guaranteed end-to-end encrypted chats with each other, and they can add each other to more and different green checkmarked group chats. Guaranteed end-to-end encryption spreads automatically and in a decentralized way.
Please read more in our revised Encryption and Security FAQ which is also contained and shipped with all Delta Chat apps, and also discusses security-relevant topics such as OpenPGP security, Metadata protection and ephemeral messaging.
If you are helping others to use Delta Chat please read the FAQ entry on when guaranteed end-to-end encryption breaks. The most common cause for encryption degradation is not an attack, but that a user re-installed the app, or installed it on another device without using the QR-code based multi-device setup flow. The FAQ gives clear advise on how to proceed. For future releases, we’ll aim to automatically prevent users from ending in such inconsistent multi-device setup states.
Lastly, for folks interested in security protocols, you may read a lot more technical and scientific background on our new SecureJoin protocols documentation site which also serves to prepare an independent security audit scheduled for 2024.
The 1.42 releases contain many other improvements, among them:
🔄 Accept/Blocked, Archived, Pinned, Mute actions are now synced across all your devices,
🗜️ Images are now compressed also on Desktop (unless you send them as files),
🖼️ Global Gallery with your pictures, documents, media across all chats, now also on Desktop
❤️ Reactions can be enabled in Android advanced settings
🐞 Bug fixes, bug fixes and more bug fixes (all dev areas got many issues resolved ) – Android went from a dozen PRs and roughly 50 issues to 5!
For complete lists of changes see:
On some stores, the 1.42 app releases might still take a while.
For Desktop, the “1.41” releases on the Microsoft store are fine to use.
We typically use even release numbers for store-releases
and uneven ones for the many intermediate ones. (meanwhile 1.42 is released everywhere)
Special thanks 💜 to Gerry, Andrea and the many other testers and
community contributors for bug hunting, triaging, discussing and helping
developers to understand and address issues.