Legacy cipher is no longer supported

[kylespencer]

Nextcloud Notes (and/or the associated Android app) appears to be generating files using a legacy cipher that Nextcloud no longer supports when server-side encryption is enabled.

After using Notes via both the web and mobile application (with a poor quality Internet connection) some note files are no longer accessible via Nextcloud. Attempts to access or synchronize the affected files (via a device client) fail with the following error:

Legacy cipher is no longer supported!

I have not yet determined the steps to reliably reproduce this problem, but I wanted to share this observation in case others have encountered this problem and can provide more information.

• Notes app version: 4.1.0 (may have also been the immediate prior version)
• Nextcloud version: 27.1.4

I am also posting this issue in nextcloud/notes#1181 in case the problem stems from the web application.