funsec mailing list archives
Re: [privacy] Digital Camera Fingerprints
From: "Marius Gheorghescu" <mariusg () microsoft com>
Date: Mon, 24 Apr 2006 11:48:09 -0700
Although the source is boingboing, that "research" is in fact valid. The CMOS sensor noise at low ISO is entirely random but as you increase the ISO, certain pixels get 'stuck' to maximum response and it's always the same pixels, assuming the temperature distribution on the sensor remains constant. They are called hot pixels. P&S cameras have small sensors and thus they begin to show this template noise much sooner than professional cameras (at ISO 200 let's say, compared to ISO 1600). But, temperature is a big factor here and can change the noise pattern, even more than the silicon impurities. A second type of camera fingerprints are the dead pixels - these remain stuck to 'on' independently of the ISO and exposure length. They are very rare in general. A third type of fingerprints is the sensor noise. Dust particles that attach to the sensor will produce a dark spot on the final image (and this changes very little depending on the lens settings). For cameras with inter-changeable lenses dust is a very common problem (but it is also very easy to remove, thus not much of a fingerprint). Then there is the type of information that is stored by the camera (time - which can be correlated), serial # (which is unique), owner information, firmware version, thumbnail data. A couple years ago there was an example where one could find edited images by comparing the image with its embedded thumbnail (certain applications "forgot" to re-save the thumbnail after the image was edited). They did a scan on the net and came up with some pretty interesting results. In conclusion, there are definitely sensor and camera fingerprints that can be easily identified given enough images. I wouldn't be surprised if sensor fingerprint would end up being accepted as evidence in court one day. There is a tool that finds hot/dead pixels but I can't remember its name right now. Its purpose is to find defects in the sensor of course, not to extract the fingerprint ;-)
-----Original Message----- From: Justin Polazzo [mailto:jpolazzo () thesportsauthority com] Sent: Monday, April 24, 2006 9:25 AM To: Fergie Cc: privacy () whitestar linuxbox org Subject: Re: [privacy] Digital Camera Fingerprints -----Original Message----- From: Fergie [mailto:fergdawg () netzero net] Sent: Monday, April 24, 2006 10:08 AM To: Justin Polazzo Cc: privacy () whitestar linuxbox org Subject: Re: [privacy] Digital Camera Fingerprints Be on the lookout for tools to "de-fingerprint" digital images -- software which can remove unique pixalization characteristics of
images
related to a given digital camera without significantly degradinging
the
image quality. :-) In fact, one would think that any given steganography software would already suffice: http://www.jjtc.com/Steganography/ --------------------------------------- And where is the re-de-fingerprinter? I bet some of that altered data will be stored in metadata by the lesser applications ;-) -JP _______________________________________________ privacy mailing list privacy () whitestar linuxbox org http://www.whitestar.linuxbox.org/mailman/listinfo/privacy
_______________________________________________ privacy mailing list privacy () whitestar linuxbox org http://www.whitestar.linuxbox.org/mailman/listinfo/privacy
Current thread:
- [privacy] Digital Camera Fingerprints Justin Polazzo (Apr 24)
- Re: [privacy] Digital Camera Fingerprints Richard M. Smith (Apr 24)
- Re: [privacy] Digital Camera Fingerprints Marius Gheorghescu (Apr 24)
- Re: [privacy] Digital Camera Fingerprints Scott Manley (Apr 24)
- Re: [privacy] Digital Camera Fingerprints Marius Gheorghescu (Apr 24)
- Re: [privacy] Digital Camera Fingerprints Dave Dittrich (Apr 24)
- Re: [privacy] Digital Camera Fingerprints Michal Zalewski (Apr 24)
- <Possible follow-ups>
- Re: [privacy] Digital Camera Fingerprints Fergie (Apr 24)
- Re: [privacy] Digital Camera Fingerprints Justin Polazzo (Apr 24)
- Re: [privacy] Digital Camera Fingerprints Marius Gheorghescu (Apr 24)
- Re: [privacy] Digital Camera Fingerprints Justin Polazzo (Apr 24)
- Re: [privacy] Digital Camera Fingerprints Andrew Blair (Apr 24)
- Re: [privacy] Digital Camera Fingerprints Richard M. Smith (Apr 24)