It's shared by everyone in the chat, When a new device needs this shared key, another device that has it will encrypt it with the new device's public crypto_box key and then upload it to the Keybase server. Those keys live in the user's signature chain A chat symmetric encryption key is 32 random bytes. The documentation doesn't mention any and I can't find it when looking around.įurther on, it explains the public keys are put into your signature chain:Īll Keybase devices publish a crypto_box public key and a crypto_sign public key when they're first provisioned. The weird thing is that there is no button to do either of this. Okay, so either we verify the symmetric key (identical on both phones), or we verify the public key (I should be able to display mine on my phone, and my friend will call up what their phone thinks my public key is, and that should match). How does this work with Keybase? Their documentation explains parts of it:Īlice and Bob share a symmetric encryption key, which they pass through the server by encrypting it to each of their devices' public encryption keys. If they match, you know (based on the open client code and the cryptography it uses) that there is no (wo)man in the middle. In Signal you check the safety number, in Wire you check the device fingerprints, and in Telegram you check the encryption key. It's pretty standard for E2EE software that the (client) code is open, the server sends you the encryption key, and you can check the encryption keys out of band. Since you can't host your own server, it has to be the Keybase, Inc's server that sends you the encryption key of your friend. But after loading the code onto your phone - installing the Keybase app - and starting a chat with your friend, you still need to verify that the server sent you the right encryption key. You've read all the code in the client, or someone you trust has done so for you. The premise of end-to-end encryption (E2EE) is that the client is secure and trustworthy, your end devices is secure and trustworthy, but the network and server need not be trusted.
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