What end-to-end encryption protects
Only the devices you and your friend authorise can read the message. The company carrying it sees only scrambled text. Think of a sealed envelope that only those devices can open — anyone who grabs it on the way cannot read it.
Here is the catch. That protection is for the message on the way. Once it reaches a device that is allowed to read it, it is unlocked there. So the real question is not "is it encrypted?" — it is "which devices are allowed to read it?"
Where a linked device comes in
Most chat apps let you add a second device — WhatsApp on a laptop, Signal on a desktop — so the same chats appear there too. It is a normal, built-in feature, and most people use it without a second thought.
A linked device is not an outsider breaking in. It is treated as you. It receives an encrypted copy and unlocks it on that device, just as your phone does. The encryption did its job; another device was given permission to read the conversation.
What German police did
They did not crack Signal or WhatsApp’s end-to-end encryption. They gained access to accounts and added a device — and new messages arrived there too. Telegram works differently: ordinary cloud chats are not end-to-end encrypted; Secret Chats are, but stay on their original devices and do not sync.
To do that, they first needed to get onto the account. Reported ways include holding your unlocked phone to scan the pairing code, grabbing a one-time text code through a phone tap, or tricking you into approving the link yourself. Germany made this a standard tactic for its agents in 2025.
To be clear, this is not a remote button that reads everyone’s chats. It needs a real foothold on your account first. But it is a good reminder that the lock on the message is not the whole story — the devices on your account are part of it too. The same lesson applies if someone can pressure you to unlock your phone.
How to check yourself (2 minutes)
Open your app’s device list and remove anything you do not recognise. In Signal: Settings → Linked Devices. In WhatsApp: Settings → Linked Devices. In Telegram: Settings → Devices.
Never approve a link request or scan a pairing code you did not start yourself. If you get a surprise "new device added" alert, treat it as a warning, not a formality. And keep a lock on the phone itself, since physical access to an unlocked phone is one of the main ways a device gets linked in the first place.
None of this means end-to-end encryption is weak — it is still the thing stopping the company and the network from reading your messages. It just means good account habits sit alongside it. The lock and the keyholders both matter.
This is general education, not security advice. It describes reported practices that can change, and app menus and the history each new device receives differ between apps and versions — check current, reputable sources and your own app settings.