[HN Gopher] Reversing a Fingerprint Reader Protocol (2021)
       ___________________________________________________________________
        
       Reversing a Fingerprint Reader Protocol (2021)
        
       Author : thejj100100
       Score  : 58 points
       Date   : 2025-07-19 22:02 UTC (4 days ago)
        
 (HTM) web link (blog.th0m.as)
 (TXT) w3m dump (blog.th0m.as)
        
       | abstractspoon wrote:
       | Excellent
        
       | Liftyee wrote:
       | Damn, I always thought that the fingerprint data was encoded
       | somehow and never left the sensor hardware itself! OS-level
       | access to the imagery seems like a security risk, but also opens
       | some interesting possibilities for alternative uses.
        
         | jeroenhd wrote:
         | AFAIK it depends per reader. This one seems to be a weird
         | webcam on steroids, but others do the matching locally.
         | 
         | IIRC, none of them do it particularly securely.
        
           | cinntaile wrote:
           | What's the security status of fingerprints on phones? Surely
           | they don't leave the security chip? I hope?
        
             | maxhille wrote:
             | I don't think fingerprints should be regarded as a secret.
        
               | ta8645 wrote:
               | Can you please post a link to high quality images of your
               | own fingerprints? It should be fine, probably nobody has
               | the technology to make them show up on a threatening
               | letter mailed to the government, or anything like that.
        
               | maxhille wrote:
               | Of course I won't, but then again I would send you
               | pictures of any other body parts the same.
               | 
               | If someone gets a hand on anything you touched, they have
               | your fingerprint. Last time you traveled to another
               | country - did you have to give them fingerprints? Is the
               | software running your phone closed source? Could you
               | ambush me at night near my house and forcefully take
               | them?
               | 
               | All I am saying is they are so weak as a secret that rhey
               | should not be regarded as one.
        
       | JJJollyjim wrote:
       | As noted in the article I reversed the protocol for a related
       | Goodix device (which was on Intel so used actual SGX instead of
       | the white-box): I used the firmware update system to insert
       | additional vulnerabilities in the sensor firmware and extract the
       | PSK from that side.
       | 
       | I did a talk about it here:
       | https://www.youtube.com/watch?v=IyjUY-xvFw4
        
       | th0mas wrote:
       | Author here, didn't expect to see this on HN today! If you've got
       | any questions, shoot!
        
         | unlucky666 wrote:
         | Do you have more posts similar to this one? Noticed your blog
         | was a bit empty...
        
           | th0mas wrote:
           | Ha yeah I should really get on updating some of the info
           | there. Got derailed with work quite a bit.
           | 
           | Most recently did some work on BitLocker:
           | https://news.ycombinator.com/item?id=42747877
        
       | ge96 wrote:
       | The real work ha underneath the software eg. I can't write a
       | camera driver but thankfully someone else can
       | 
       | That's cool the raw data image GIMP
        
       | johnflan wrote:
       | I didn't follow the byte ordering of the image format at the end.
       | Anyone have an explanation?
        
       ___________________________________________________________________
       (page generated 2025-07-23 23:01 UTC)