Who needs a whole blockchain? Just basic public-key cryptography would do the job.

Imagine if you will, that the NVR (recording system) has a unique private key flashed in during manufacturing, with the corresponding public key printed on it's nameplate. The device can sign a video clip and its related meta-data before exporting. Now, any decent hacker could see possible holes in this system, but it could be made tamper-resistant enough that any non-expert wouldn't be able to fabricate a signed video. Then the evidence becomes the signed video and the NVR's serial number and public key. Not perfect, but probably good enough.

Unfortunately consumer devices often have weak cryptography built into them. The one properly implemented are just out of reach for average consumer.

More than just a blockchain, you need a decentralized set of oracles to mutually corroborate information. https://polykey.com/blog/ai-detection-versus-cryptographic-p...