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[liberationtech] iPhone5S Fingerprint and 5th amendment

Joseph Lorenzo Hall joe at
Wed Sep 11 10:27:42 PDT 2013

On 9/11/13 12:08 PM, Eugen Leitl wrote:
> On Wed, Sep 11, 2013 at 11:04:44AM -0500, Matt Mackall wrote:
>> Similarly, any other sort of one-way algorithm that prevents you from
>> reconstructing a valid input from the stored data is not going to work.
> Typical fingerprint matching uses classification, recognizing and
> encoding multiple features into a vector. You could use a one-way
> hash on that vector. This is likely subject to a precompiled hash
> lookup table attack, as the number of all possible fingerprints,
> quantized via a classification vector is not that large.

There's a good deal of existing research out there on using symmeteric
hashes -- a hash that can accept discrete inputs in arbitrary order and
always calculate to the same value -- for secure biometric template
storage and matching.

Here is a paper I point people to that many of you will find absolutely
fascinating (although it's been some years so do check citations
pointing to this for further work):

Sergey Tulyakov, Faisal Farooq, Praveer Mansukhani, & Venu Govindaraju.
(2007). Symmetric hash functions for secure fingerprint biometric
systems. Pattern Recognition Letters, 28(16), 2427–2436. Retrieved from

Joseph Lorenzo Hall
Senior Staff Technologist
Center for Democracy & Technology
1634 I ST NW STE 1100
Washington DC 20006-4011
(p) 202-407-8825
(f) 202-637-0968
joe at
fingerprint: BE7E A889 7742 8773 301B 4FA1 C0E2 6D90 F257 77F8

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