They would, but each camera’s private key can be extracted from the hardware if you’re motivated enough.
If Alice’s fancy new camera has the private key extracted by Eve without Alice’s knowledge, Eve can send Bob pictures that Bob would then believe are from Alice. If Bob finds out that Alice’s key was compromised, then he has to guess as to whether any photo he got from Alice was actually from Eve. Having a public timestamp for the picture doesn’t help Bob know anything, since Eve might’ve gone and created the timestamp herself without Alice’s knowledge.
Still, unique keys for each camera would lessen the risk of someone leaking a single code that undermines the whole system, as happened with DVDs.
And if an interested party wanted to steal a camera’s private key to fake an image’s provenance they’d need to get physical access to that very camera. Perhaps a state-sponsored group could contrive this (or intervene during manufacturing), but it is a challenge and an even bigger challenge for everyone else.
Physical access means all bets are off, but it’s not required for these attacks. If it’s got a way to communicate with the outside world, it can get hacked remotely. For example here’s an attack that silently took over iphones without the user doing anything. That was used for real to spy on many people, and Apple is pretty good at security. Most devices you own such as cameras with wifi will likely be far worse security-wise.
Maybe each camera has a different public/private key?
They would, but each camera’s private key can be extracted from the hardware if you’re motivated enough.
If Alice’s fancy new camera has the private key extracted by Eve without Alice’s knowledge, Eve can send Bob pictures that Bob would then believe are from Alice. If Bob finds out that Alice’s key was compromised, then he has to guess as to whether any photo he got from Alice was actually from Eve. Having a public timestamp for the picture doesn’t help Bob know anything, since Eve might’ve gone and created the timestamp herself without Alice’s knowledge.
Still, unique keys for each camera would lessen the risk of someone leaking a single code that undermines the whole system, as happened with DVDs.
And if an interested party wanted to steal a camera’s private key to fake an image’s provenance they’d need to get physical access to that very camera. Perhaps a state-sponsored group could contrive this (or intervene during manufacturing), but it is a challenge and an even bigger challenge for everyone else.
Physical access means all bets are off, but it’s not required for these attacks. If it’s got a way to communicate with the outside world, it can get hacked remotely. For example here’s an attack that silently took over iphones without the user doing anything. That was used for real to spy on many people, and Apple is pretty good at security. Most devices you own such as cameras with wifi will likely be far worse security-wise.