Allow to regenerate autocrypt key

deltachat / deltachat-core

Delta.Chat C-Library with e2e chat-over-email functionality & Python bindings

https://c.delta.chat

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Allow to regenerate autocrypt key #399

Open hpk42 opened 5 years ago

hpk42 commented 5 years ago

right now i am in the situation that i'd like to change my key for my delta account but i also don't want to have lots of unreadable mail. Autocrypt does not yet provide a mechanism for key rotation. Maybe i get to discuss this at the upcoming OpenPGPSummit with @dkg @valodim @azul ...

For Delta i guess:

a new PGP key could be generated and would be sent out with new messages
messages erncrypted to the old key remain readable as long as the "old" autocrypt key is still used for decryption (that's the case already, right? -- not quite sure how the "keystore" for delta works)
potentially we could send a proactive MEMBER_CHANGED_SETUP event out to all DeltaGroups and chats (this message/event is in consideration for other evolving countermitm thoughts on updating verified keys)

azul commented 5 years ago

@hpk42 why do you want to replace your key? In some scenarios changing the current key might also be an option:

to add a new encryption subkey
to postpone the expiry of the key

As long as the key used for certifying the other keys stays the same there's no need to replace the entire key.

hpk42 commented 5 years ago

to be honest -- my current key has a random uid and my mutt-setup is still not happy with that (lack of muacrypt/mutt integration, really) and so i thought i'd like to quickly change my key but don't want the disruption. So it has no real security reasons -- let's just say i am "for some reason" unhappy with my current key :)

azul commented 5 years ago

@hpk42 you can also add a new uid and revoke the old one. That way you keep the same fingerprint and all. No idea how delta stores your key. But maybe the setup message flow could be used to inject the updated version of the key into delta.

hpk42 commented 5 years ago

On Thu, Oct 18, 2018 at 04:41 -0700, azul wrote:

@hpk42 you can also add a new uid and revoke the old one. That way you keep the same fingerprint and all. No idea how delta stores your key. But maybe the setup message flow could be used to inject the updated version of the key into delta.

yes -- i am sure i could hack up something.

But the general question of (howto) sending key updates remains. The most general flow is to provide a complete new key, for example if you are unsure (or if you are certain) that your old private key was compromised/leaked.