At 11:52 PM 8/24/04 -0400, Dave Emery wrote: > Just a random distraction from the normal topics (but not >completely irrelevant either)...
Highly relevant sir. > He told me that especially in the low end camera market NO >sensors used were completely free of anomalous pixels (black, white, >dim, bright etc) and much of the actual processing in digital camera >firmware was related to masking or hiding the inevitable defects which >apparently can include (at least in CMOS sensors) entire rows or columns >that are bad. Kinda like disk drives and DRAM arrays. Its all about yield. Covering up mistakes transparently. > This got me thinking - clearly these concealment patches are not >completely undetectable in families of (multiple to many) images taken >with the same exact camera... and for the most part the defects are born >with the sensor and change little over time if at all. And with few >exceptions they are random, and different for each sensor. Perhaps, but the jpeg-ization might lose these, or at least the image "unicity distance" might require many more pictures than a careful steganographer will publish. > Cypherpunk relevance (marginal perhaps), but the ability to say >that a particular image or set of images came from a particular camera >COULD have legal consequences for those bent on activities someone >thinks of as unfriendly to their interests... Very relevant, traffic analysis and fingerprinting (intentional or not) are always tasty subjects. One question for the court would be, how many *other* cameras have column 67 disabled? One of every thousand? And how many thousand cameras were sold? Pope Major Variola (ret)
