Borg Backup always asks for the key passphrase when accessing a repository which was initialized in authenticated or authenticated-blake2 mode (see borg manual).

However, it should in principle be possible to read data from such a repository without knowing the passphrase (albeit without any authentication guarantees). Does borg offer a way of doing so?

  • 1
    To decrypt encrypted data, you will need to be in possession of the key.
    – Kusalananda
    Apr 14 '18 at 14:54
  • @Kusalananda Yes, I'm aware of that. But in authenticated mode, borg does not encrypt the data, the key is only used to generate and verify HMACs for cryptographic integrity checking. Apr 14 '18 at 15:16

Does borg offer a way of doing so?

I am unaware of this capability within borgbackup.

You are correct that there is a theoretical possibility/likelihood the data is readable because it isn't actually encrypted -- simply hashed for integrity verification.

This does not mean the application has a mechanism for doing so, which is what your question is actually asking. The documentation does not indicate anything like this functionality.

I assume you are interested in accessing the data regardless if borgbackup itself actually has the functionality. If yes, read on.

"That is not possible" is a valid answer -- This doesn't mean you are out of luck reading the data, but you are probably not going to use borgbackup tools if you succeed. I would suggest applying standard search, text processing, expression matching, etc. tactics to the data on disk that borgbackup has archived, and see what you can come up with.

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