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Keyfile Strength and Security

Technical Topics
Brian Anderson
2020-10-31
2020-11-01

  • Brian Anderson

    Brian Anderson - 2020-10-31

    The math in the Technical Details of the user guide is over my head, but I like the idea of using keyfiles. Can anyone help with these questions?

    For these questions, please assume we are using VeraCrypt-generated keyfiles (with high entropy) and assume that an adversary can never access the keyfiles (the adversary would have to brute-force or use another method). These questions are about the theoretical strength of keyfiles, not about practical concerns of adversaries possessing your keyfiles.

    1. Is there a way to compare a keyfile’s strength to that of a password? For example, is it possible to figure out something like “using a 10 KB keyfile (and no password) is as strong as using a 40-character password (with no keyfiles).”

    2. Is there a difference in strength between one and multiple keyfiles if the total size is the same? For example, does one 500 KB keyfile provide the same level of security as five 100 KB keyfiles?

    3. Are there performance issues associated with using several keyfiles that are each 1 MB in size? The user guide says that only up to the first MB of a keyfile is processed due to performance issues, but we can have as many keyfiles as we want. Does using multiple 1 MB keyfiles cause the same problems that would happen if VeraCrypt processed more than the first MB?

    4. Do we get diminishing returns in strength with keyfile size (or number of keyfiles) and is there a way to calculate it? For example, is using a 200 KB keyfile 200% as secure as using a 100 KB keyfile, or only 175%?

    Thank you in advance for your help!

     

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