I would also like to know more about why you think Borg's encryption is questionable. I'm not familiar with Borg's internals, but there's not much one could do

I would also like to know more about why you think Borg's encryption is questionable. I'm not familiar with Borg's internals, but there's not much one could do wrong here, as it should just be simple symmetric encryption. Does it not use a strong cipher? Is the cipher used incorrectly? Is the key derivation method weak?