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Comment by DanielBMarkham | Hacker News Reader

You can require biometrics and still not record them. Just use them as a hash lookup into a keystore. The biometric itself would only exist on the server for a few cycles while the key was being looked up. (Very similar to the way credit cards are done)

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Just use them as a hash lookup into a keystore.

This is intuitively appealing, but do biometrics really boil down to an exact number that we could hash like this? (Genuine questions; I don't know.) It seems more likely to me that biometric measurements would be considered to "match" when they're within particular tolerances. This is an operation you can perform on the original measurements, but not on hashes of those.

There is a cryptographic tool called a "fuzzy extractor" that solves this problem (c.f. Fuzzy Extractors: How to Generate Strong Keys from Biometrics and Other Noisy Data, by Dodis, Reyzen and Smith [0]). At enrollment time, you compute some (non-sensitive) data P = Enroll(biometric). Then every time you compute Recover(P, biometric') you will get the same (high-entropy) output, as long as biometric' is close enough to biometric.

[0] https://www.iacr.org/archive/eurocrypt2004/30270518/DRS-ec20...

It is, effectively, what Touch ID does. (It's an over simplification but as an analogy it works)

Unfortunately, that's not how governments around the world require it right now. Estonia for its e-citizenship program, as well as pretty much all countries requiring a fingerprint for passports store the fingerprints in their own centralized database (that also get shared with other nations).

I switched my phone fingerprint to another finger for my phone as soon as I signed-up for a passport.

Wow.

So a piece of plastic the bank gives you with mostly arbitrary numbers on it is better protected than your own fingerprints, which you're stuck with for life?

Good grief.

In the Netherlands we had a passport with fingerprint, and all data stored by the state. Luckily, this was reversed, and now the fingerprint is only stored in the passport itself. Well, that's what I hope, as the fingerprint needs to be stored temporarily for the time to create the passport.

Better, if you don't leave the EU, you can use an identity card that doesn't have the fingerprint.

I was lucky enough to have an old passport that just spanned the period in which the fingerprint was stored centrally. Now I have an ID card, but one time in the future I will leave the EU, and then I have to get a password...

This sounds like a good idea on the surface but this just shifts the problem.

Ultimately, you still only have 10 fingers (general assumption), and not a large space like 30 char passwords.

However, Fingerprints cannot be practically hashed.

Images can be hashed(and hashed in such a way that minor changes can still lead to the same hash), so images of fingerprints should be hashable.

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