Nikon has issued a Notice of Temporary Suspension of the Nikon Authenticity Service. This is because the company realized there was an issue with C2PA implementation on the Z6III mirrorless camera.
In a post on the Nikon Imaging Cloud, the company stated, “We have confirmed that an issue has been identified in the Nikon Authenticity Service. In response to this confirmation, the service has been temporarily suspended while we work diligently to resolve the issue. We will provide an update as soon as the corrective measures are complete. We sincerely apologize for any inconvenience this may have caused.”
What is C2PA?
C2PA (Coalition for Content Provenance and Authenticity) is a project to develop technical specifications on content provenance and authentication. Nikon released firmware 2.00 for its Z6III mirrorless camera a couple of weeks ago. This update added some great new features for video and stills shooters.
One of these improvements was also the addition of support for the Nikon Authenticity Service. The Nikon Authenticity Service enhances content credibility by using provenance information and other data in accordance with the C2PA standards.
What is the issue?
Unfortunately for Nikon, a user named Horshack on the DP Review forums discovered a way to circumvent the C2PA protections on the Z6III. The camera has a multiple exposure feature that lets you take several images and blend them together into a single out-of-camera JPG file. Using the Overlay option within the feature, you specify the first image to blend by selecting a RAW file on the media card in the camera. You can then overlay other images from the camera on that image. However, Horshack found that if you overlaid a non-C2PA certified image with a C2PA-certified image, the result was incorrectly approved as C2PA compliant.
Horshack used two Nikon Z6III cameras, one of which was C2PA-enabled, while the other was not. With the non-C2PA camera, he photographed a graphic which read “Hacked by Horshack!” Next, he put that memory card into his second, C2PA-enabled Z6III. Using the Multiple Exposure feature, Horshack set the number of exposures to 2 in the Overlay mode. Finally, he took a blank image with the lens cap on with the C2PA-enabled Z6III. The resulting multiple exposure image showed the first image as it was taken, unaffected by the blank image. However, the final output image had the C2PA authentication and so was passed as genuine by the Content Authenticity Initiative’s (CAI) online verification tool.
What does this mean?
The vulnerability discovered by Horshack has potentially serious implications. Someone could combine an AI-generated or altered image with a C2PA-authenticated image using the method. This would result in a final version of the AI image, which would pass online checks as a genuine image.
What we think
The widespread use and sharing of deepfakes and other AI-images is a very real issue. Initiatives such as C2PA are important to ensure that we can be confident that any images we see are genuine. Nikon took a step towards that end by introducing support for the Nikon Authenticity Service with the recent update to the Z6III. As such, it’s a shame that this vulnerability was overlooked. However, it’s inevitable that loopholes will pop up from time to time as we move towards an effective system of content authentication. Hopefully, Nikon will find a solution to this stumbling block quickly and reinstate its Authenticity Service soon.
