[cryptography] Privacy-Preserving Photo Sharing via crypto

Michael Nelson nelson_mikel at yahoo.com
Fri Apr 12 19:02:50 EDT 2013


>
http://www.usc.edu/uscnews/newsroom/news_release.php?id=3017
 
I didn't read more than the above, but one imagines
that the trick is in handling compression.  With bmp, the following immediately comes to mind: Take a seed, generate
a mask and xor it with the bmp pixels.  Now the pic is white noise of the right size.  Give the seed to your friends and they can
recreate the original bmp.  But need to
handle jpg etc. for the size.  If you
convert to bmp and do the above, you can't compress it back to something
small.  OTOH, depending on how you mangle the jpg data, it
either won't expand, or  it expands with certain patterns the constitute leaks of information.

My guess is that
their solution is not perfect.  Indeed they say that without the permission you get "a degraded, unrecognizable mess" -- clearly less than pseudo-random.
 

> USENIX proceedings yet though. However, somewhat
disturbing though that
> software developed via NFS grants on the U.S.
taxpayer's dime can be
> patented.
 
In this sort of thing, the US govt retains the right to
unrestricted use throughout the world, so the tax payers normally get something from the patent.  In this case, since the main point is porn,
you're right -- the taxpayers get nothing...

Mike
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