Apple released a blog post on September 15, detailing the Apple Reference Image feature introduced on devices such as the iPhone 18 Pro and iPhone 18 Pro Max, which supports pixel-level annotation of real image data.

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Pressing the shutter button signs it within the SEP, creating a "digital negative"

Apple Reference Image is an optional mode (Reference mode) that provides hardware-level verification and timestamp binding when taking a photo, ensuring the image comes from a genuine sensor, is tamper-proof, and resists AI-forged images, suitable for news organizations and evidence preservation scenarios.

In terms of technical implementation, when the user presses the shutter button, the system signs key metadata (such as focal length, digital zoom, etc.) in the SEP (Secure Enclave Processor), forming an unforgeable "digital negative" information. Regarding timestamps, the system provides lower and upper bound timestamps for the shooting time, and encrypts the timestamp service to embed it into the reference image, ensuring the accuracy and verifiability of the image's time.

After signing at the sensor level, Apple will also work with the private cloud service (Private Cloud Compute) validation chain to ensure it is tamper-proof throughout the entire process, while protecting user privacy and not exposing personal information.

From "sign after taking the photo" to "sign while taking the photo"

In usage scenarios, this feature can counter AI-generated content and provide an evidence chain of "authentic source" for news organizations, evidence preservation, and situations requiring trusted image sources. Compared to traditional post-processing metadata-based evidence systems (usually signed after editing), Apple Reference Image completes hardware-level signing and timestamp binding during the shot, theoretically making it harder to tamper with and improving credibility.