Let devices request keys to decrypt past history for a room.

[ara4n]

If I'm in a room as device A, and join it later as device B, i need a way to request the old room key data from device A.

Similarly if I'm invited into a room by someone and they want to share past history with me, they need a way of transferring key data.

[apexo]

Could a possible solution to this be:

• create a special (maybe hidden per default) per-user channel on the user's home server
• each new device sends an (encrypted) poll message to all other devices (via this room)
• all other devices reply with the encrypted e2e state (sans identity keypair), or just all keys required for decrypting room history

[ara4n]

@apexo this is sort of the plan, except we now have a dedicated "to device" store-and-forward API for sharing data like this, which is encrypted in turn by olm. Also, we'd probably request the historical ratchet state from a specific device rather than all of them, and require the target user to approve/deny the request. e.g. "Matthew has added a new device 'iPad' and is requesting room history since Sept 18th. Do you want to share history?" or something.

[DrFlamingoo]

@ara4n So I am currently in a room listed with seven devices from three machines and as many browsers. well, I guess vector --> riot transition helped to increase the number. But with only one other person in the room, this is cumbersome.
I would prefer if a client-side certificate could be recognized as a user, and verification becomes an automated process that does not rely on devices or interaction of members in the room and I just see the history. Would work on private devices (i.e. not the library computer).
To understand the process, how are the IDs generated, and how long are they kept / stored? Do they change with version change of kernel, browser or if I purge cookies? I am pretty sure I am missing discussions on the same device I logged in at the time...

PS: I haven't seen another issue / discussion on this matter, so I hope this is the right place to put this :)

[madduck]

Maybe look at Bitcoin wallets, e.g. http://wallet.counterwallet.io, which ask a 12 dictionary word passphrase from the user. That passphrase is the private key.

Now when I log in to a device, I could be asked if I wanted to create a device-specific key, or if I wanted to instate the user's key from such a passphrase.

[csmart]

Can I check my understanding please, does the following represents current expected behaviour?

Say I'm in a room which has encryption turned on and we're all happily chatting away and everyone has verified keys. Then I sign out of riot and back in to see that all previous conversations are encrypted again and that there's no way to get the original key to you, so history remains unavailable?

Thanks!

[madduck]

It doesn't matter whether keys are verified. The point is that the encryption algorithm (megolm/ld double ratchet) encrypts to the current keys of all the people present.

Now if you log out of Riot, your key is discarded from local storage, and upon rejoining, a new key is made. Future messages will now be encrypted (also) to that key, but since you no longer have access to the previous key, the old messages aren't accessible any longer.

The solution is IMHO to allow one to export/safe/backup one's key and restore it upon rejoin.

[csmart]

Right, thanks @madduck

I've been having major usability problems with end to end encryption in riot, and I didn't realize that it was because logging out deletes your session key! riot-android/#869 would be nice, because I had no idea!

Now that I understand why I've been losing my keys -- and being locked out of my chat history -- I have to say I'm really annoyed. I'm sure everyone agrees you shouldn't have to stay logged in to your chat program continuously in order to be able to use it reliably. It's one thing to hide past messages from newcomers to a channel, but this same issue means that I can't share decryption keys with myself! In my opinion, E2E should not have been rolled out as a feature before this problem was solved. It's been a trainwreck for everyone I know who's tried turning it on.

[csmart]

@kebertx Aside from this issue (which I now understand) e2e has been awesome for me and those I've been chatting with.

IIRC, it was advertised as beta and at least in the Android app it says it's that e2e is an "experimental labs feature which may break in unexpected ways." So I think the warning has been fair enough.

Having said that, I do think things can be improved (a simple warning about losing keys when signing out, for example would be handy for new users).

IMO, it's been great to have the feature early and be able to test it.

[madduck]

Hey @kebertx, sorry you've had a bad experience. It is true that e2e at the moment is highly beta, and things certainly need to be improved, which is, in part, why this issue exists.

FWIW, I see no need to ever log out. I do have riot.im exempted from my cookie munger, and so I don't have this issue. Similarly, I don't log out the Android app, but the problem will come when I need to switch to a new phone, and by then I hope they've got a fix.