Date: Fri, 10 May 2019 09:20:54 +0000 From: halfdog <me@...fdog.net> To: oss-security@...ts.openwall.com Subject: Re: Re: fprintd: found storing user fingerprints without encryption Roman Drahtmueller writes: > [...] > > > I am not insisting that encryption key should be on the disk or is > > encrypted with a static key that is embedded in the binary. > > Instead, we can make fprintd to use a TPM, if available. > > > The problem persists: The encryption key must be available for the FP > data to be accessible, and so it is for an attacker. It doesn't matter > where you store the key. > > A TPM (and, transitively, products that encrypt with TPM-sealed or > TPM-bound key material) is good for the situation where the system is > physically stolen while powered down (or the drive fails). But that's not > our problem here. Therefore dedicated tamper-proof IC-designs+embedded software exist, that perform the biometry template storage and matching on the chip (MoC). There are some vendors out there providing such hardware + MoC-algorithms, but mainly fingerprint and some iris biometry variants seem certified so far. These are intended for access cards or USB-tokens in two or more-factor authentication schemes in a 1-to-1 match fashion, not as centralized 1-to-many matching schemes also deployed rarely (e.g. in Japan where they really like biometrics as long as you do not have to touch the biometry reader ...). > [...] > > > Otherwise, but even though it is not perfect, it would be better to apply > > the fingerprint data protection, such as keyring or access control, rather > > than raw fingerprint template. > > FYI, Windows Hello might use Next Generation Cryptography (called CNG) to > > protect and store user private data and encryption keys. > > There are not many options left to solve the stored credential problem, > and it should be clear that saving a file, encrypted or not, is not the > solution. > > One possible solution is to use a hash algorithm, potentially cost-based, > to derive a bit string (that is suitable for comparison with the > persisted authoritative string) from the output of a fingerprint reader. At the momenent I do not know of any algorithms providing sufficient entropy binary hash data from fingerprints in a reliable way. Changing extraction to deliver more entropy results in higher FNR during authentication step later on, I think. > [...] When working on a project to provide highest security MoC solutions with Linux (for other type of biometry, not fingerprints), Nitrokey was offering an open-source USB-token hardware (even the PCBs are open source, if I remember correctly). That platform seemed closest to be a good starting point for developing such an open source MoC biometry solution as they sell also one part with a certified tamper proof trusted element that seemed to allow performing biometry template storage and comparison on chip if programmed correctly. Time in the project was too limited to explore, if that hardware would REALLY allow to upgrade it to a powerful, highly secure but still affordable open source biometry system for use by journalists, human rights activists, NGOs ... and nerds, e.g. for password+biometry secured full disk encryption schemes. > [...] hd
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