How is WhatsApp end-to-end encrypted if you can access the messages on multiple devices even if the last active device is offline?

Question

I don’t know whether I phrased the question properly. Let’s say I opened WhatsApp on my laptop after I went offline on my mobile. The last messages I received or sent are still shown on the WhatsApp on my laptop. If it’s truly end-to-end encrypted, how does it sync messages between different devices without a connection between them?

In: Technology

Answer 1

Imagine you have a secret box where you put your letters. You give each person a key that can only open the box when it’s in their hands. Even if I have a copy of all the keys, I can’t read what’s inside unless I have the exact key for that message. WhatsApp uses this kind of box but for messages instead. Each phone has its own key and can read the messages. Even if one phone goes offline, the messages are still encrypted until the next active phone decrypts them.