this post was submitted on 21 Nov 2023
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Maybe I am misunderstanding here, but what is going to stop anyone from just editing the photo anyway? There will still be a valid certificate attached. You can change the metadata to match the cert details. So... ??
I don't know about this specific product but in general a digital signature is generated based on the content being signed, so any change to the content will make the signature invalid. It's the whole point of using a signature.
I was too tired to investigate further last night. That is the case here, sections of data are hashed and used to create the certs:
https://c2pa.org/specifications/specifications/1.3/specs/C2PA_Specification.html#_hard_bindings
Which means that there isn't a way to edit the photo and have the cert match, and also no way to compress or change the file encoding without invalidating the cert.
so it's for jpeg shooters, basically. unfortunately the leica bodies aren't really known for producing good jpegs.
I'm not expert in encryption, but I think you could store a key in the device that encrypts the hash, then that encrypted hash is verified by Leica servers?