I use GPG to symmetrically encrypt multiple files, and it would be more convenient if they all had the same strong passphrase. It's possible that someone could gain access to several of these files.

In this situation, I don't care if getting the passphrase for one of the files gives access to the others as well.

Is it safe to use the same GPG symmetric passphrase for multiple files ?

If needed, please assume --cipher-algo AES256, --s2k-digest-algo SHA512 and --s2k-count <something_big_enough>.

  • 2
    To be clear, you're trying to determine if having access to multiple ciphertexts gives an attacker a better chance at figuring out the decryption key? – Boycott SE for Monica Cellio Feb 16 '17 at 22:33
  • There's some info in this thread on the key derivation function used by GPG which might answer part of the question crypto.stackexchange.com/questions/12321/…. I say part, because it doesn't talk about AES encryption mode, the use of random IV, etc. – Sunil Agrawal Feb 16 '17 at 22:51
  • Yes, that's right. I'm concerned about pure crypto problems, not about the usual problems of password reuse. – Hey Feb 17 '17 at 0:23
  • I have the same question and wasn't able to find answer yet. It could be rephrased as "Is it easier to crack 2 files when we know that both have the same gpg AES passphrase when comparing to single file?" – bubersson Jun 16 '19 at 23:00

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