Connecting session to Key Backup does not work

[Olf0]

Steps to reproduce

1. Where are you starting? What can you see?
   
2. What do you click?
   [Connect this session to Key Backup] button
3. More steps…
   Inputting the correct passphrase or, alternatively Backup Key (confusingly called "Security key" in that dialogue; please do unify the wording) always yields:
   
   or
   
   ultimately result in
   
4. Counter-check
   Importing the Key Backup between the Android apps Riot.im and miniVector works fine (in either direction, both directions tested), both via passphrase and via Backup Key.
   I.e., these four test worked absolutely fine.

Outcome

What did you expect?

Backup keys are imported.

What happened instead?

Error message, as depicted above.

Additional information

As mentioned in step 5 above, the key backup was generated and successfully connected to between the older Android clients miniVector 0.9.12 and Riot 0.9.13. Newer Matrix clients do not support Android 4.4, hence cannot be installed.

It looks like the format and maybe also the encryption (originally m.megolm_backup.v1.curve25519-aes-sha2) was altered; nevertheless, modern clients (like the elements web-app used) shall be able to use / import the old format / encryption!

Operating system

Ubuntu 20.04 LTS (x86-64)

Browser information

Firefox 116.0.2 (64-bit)

URL for webapp

https://app.element.io/#/room/!xyz:matrix.org

Application version

Element version: 1.11.38 Olm version: 3.2.14

Homeserver

matrix.org

Will you send logs?

Yes, if requested / required.
IMO this is unambiguous without logs, so I did not generate and submit them now.

[richvdh]

Unfortunately we have no plans to support the old backup encryption format.

[Olf0]

Not even having considered backward compatibility when altering the backup format is …, as this reassigns all old backups to be "one way backups", i.e. useless, random data.

IMO there is no better way to lecture people that creating backups is a superfluous, futile effort.

[richvdh]

Sorry, I don't know what I was smoking last week. m.megolm_backup.v1.curve25519-aes-sha2 is the current key backup algorithm. (MSC3270 proposes a new algorithm, but that's not yet live. And yes, we will need to consider backwards compatibility.)

So there is something different going on here. If you can still reproduce it, please submit debug logs from within the application.

[Olf0]

Thank you for rereading, reinvestigating and reconsidering this issue.

So there is something different going on here. If you can still reproduce it, please submit debug logs from within the application.

I will try to (reproduce it again, which should not be an issue) and to "submit debug logs from within the application" (never did that before with the Elements web-app. Edit: Found the dialogue for that.).

[schildbach]

This might be related to #23497.

[richvdh]

Hi, I'm going to close this issue for now as there is not enough info here for us to be able to action it. Please feel welcome to reopen or ask me to reopen the issue if you update the description with steps/screenshots/video/more details so our developers can have a look at it.