How end-to-end encryption works: why even WhatsApp cannot read your messages
End-to-end encryption: how a message stays locked all the way to your friend's phone
With end-to-end encryption, every message goes through the company's chat server. But the company cannot read it. Where is the lock put, and who holds the key?
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Before the message leaves, your phone scrambles it with a key, a long secret number. Only someone with the same key can turn it back into words.
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Then it goes out locked for the trip as well, as in any careful app. The scrambled message now rides inside the lock of the trip.
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At the server, the lock of the trip comes off, as before. Under it, Rono finds only the scrambled message. The server has no key for it, so it just passes it on.
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Miva's phone holds the same key. It turns the noise back into your words, and Miva grins.
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The lock went on at one end of the chat and came off at the other end, and nowhere in between. This is end-to-end encryption. WhatsApp has used it for every chat between people since 2016, and Signal has from the start.
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One thing does not add up. Your phone and Miva's hold the same key, and they never met. When you pressed send, Miva's phone was even switched off, in her bag.
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Quick check
A court asks the chat company for your message to Miva.
Show the answer
At most the scrambled message, and only while the server still holds it. The key that opens it lives only on your phone and Miva's.