Forging verified digital photos

Earlier this week, Dmitry Sklyarov, a security researcher at Russian security vendor ElcomSoft, gave a talk on how he managed to hack the Original Decision Data technology that Canon uses in its high-end cameras. You can get the presentation that he gave at CONFidence 2010 here.

ODD uses an HMAC to verify that digital photos haven't been modified. I've heard that news agencies use this technology to verify that photos that they use are authentic, but I haven't found anyone who can verify that this is actually true. 

It turns out that a camera isn't a hardware security module that's designed to protect the key that it uses to calculate the HMAC.  Because of this it's relatively easy to extract the key from a camera and then use it to create tampered photos that will pass as authentic because they have an HMAC that indicates that they haven't been tampered with.

To show that it works, the people at ElcomSoft had some fun with their hack, and made some pictures of things like an astronaut planting the USSR's flag on the moon and a flying saucer over Mount Fuji, all of which will verify as being untampered with. You can see those here. (You'll have to scroll down to see the hacked pictures.)

Maybe it's a bit premature to trust technologies like ODD yet. I certainly wouldn't want them allowed as evidence in court.

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