No way to change password for a backup set

[Jonathan Davies]

In deja-dup-preferences, there is no way to change a password for a backup set - without starting the backups again from 0.

[Michael Terry (mterry)]

I agree this is the case and that it would be nice if it weren't so. But one thing that Deja Dup assumes is that it can't run code on the backend (due to support for cloud locations like Amazon S3 and Ubuntu One).

So it would involve downloading all the files, un-encrypting, re-encrypting, uploading, deleting old ones... A complicated, lengthy, error-prone thing.

So while I agree this would be nice, it's not on the roadmap for now.

[Eero (eero+launchpad)]

Better way of encrypting backups would be something like this:
1. Generate a random key for backup encryption.
2. Encrypt the generated key with a password provided by the user.
3. Save the encrypted key with backups.

Now if the user wants to change the password, only the key file needs to be re-encrypted. That is more or less how LUKS works. As an added bonus better key derivation functions for step two can be easily added over time with a scheme like this.