The article says the law will sunset in 2023. That is when it expires, not when it begins.California has banned political deepfakes during election season.
Also banned: pornographic deep fake videos, so no longer Nicholas Cage on Stormy Daniels face.
The law becomes applicable in 2023.
You digitally sign a video using a hash of the contents and your public key. That establishes where the data came from. Any changes to the file, like replacing faces, changes the content hash, so the signature won't match. Unsigned media is treated as hearsay. It's not technically difficult, but nobody is really set up to do it yet.I suppose they're going to have put public keys in the metadata with source tracking or something along that line, and any media without the properly formatted and secured metadata will be inadmisible in courts. Won't THAT be fun!