Representing a physical product as a unique cryptographic hash that the consumer can independently verify is generally a lot harder than attaching a photo. From a comment below: > Leanne Kemp, an Australian who in 2015 founded a company called Everledger, has now encrypted the distinguishing features of 1.8 million diamonds and their provenance on a blockchain. > More than 40 features are logged to create a fingerprint for each diamond, logging it from mine to ring.

For this to provide proof of authenticity, I need to be able to visit a jeweler not employed by Everledger, and have them be able to use a rubric to classify my diamond along these 40 features in a way that uniquely describes it in a way no other diamond could be described. I then need to be able to visit a second and a third jeweler and obtain the exact same classification along these 40 features.

When visiting Everledger's site, I can't get any information on the classification process beyond that sentence. The supposed core of the product doesn't even have a white paper.

Diamonds are comparatively easy to classify, as they are supposedly unique in many ways, and don't physically degrade over time. When it comes to tins of milk, I can't think of a secure proof of authenticity process that doesn't involve the consumer verifying the composition of the product with a gas chromatography machine.

Yes, I should have attached a disclaimer that I do not claim that a photograph would be enough to verify the safety of infant formula. Fair points.