Nikon's image authentication algorithm cracked

Researchers have discovered a flaw in the system used by Nikon professional digital cameras to ensure images have not been tampered with.

Normally, in high-end SLR digital cameras a unique and encrypted signing key is appended to an image when it is taken, which is verified in Nikon's case by its proprietary Image Authentication System. If an image is edited this key will be overwritten, an action that will be picked up by the software.

Russian company Elcomsoft, however, said that it has found a way to extract the original verification key so that it can be attached to any image regardless of whether it has been edited or not.

The security hole is said to affect all Nikon digital cameras supporting the verification system, specifically the D3X, D3, D700, D300S, D300, D2Xs, D2X, D2Hs, and D200 SLRs.

The company has not offered full details of how it discovered the issue, but has published tampered proof-of-concept images to back up its claim, including one superimposing the Beatles' Abbey Road album cover against a scene of Russian countryside. All were passed by Nikon's software as genuine, Elcomsoft said.

The revelation comes only months after the company found a similar flaw in the system used by photography's other leading vendor, Canon, to verify images from its professional cameras. The Russian firm claims that this issue remains unaddressed by Canon.

Image verification systems were designed to make digital images admissible in court as well as calm the nerves of photographic agency heads worried about image fakery. Part of the security problem is that for reasons of secrecy as well as commercial gain, Nikon and Canon's software is proprietary. This makes it harder for independent researchers to spot design flaws short of reverse engineering the technology, as a criminal hacker.

Elcomsoft has a controversial history in finding flaws in the security systems used by companies making well-known products. This has included finding security holes in backup program used by Research In Motion's BlackBerry, Apple's iPhone and most contentiously of all, selling a program that could "recover" Wi-Fi encryption keys.

However, the company has no plans to profit from its latest revelation, said Elcomsoft marketing and sales director, Olga Koksharova.

"It was just a pure security research," she said. "At first, we were sure Nikon would be interested in it and would somehow act together with us. However, they didn't reply to us for quite a long time and so we decided it might be interesting at least to the world."

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