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01 September 2022

BFG004: verified recording

With sophisticated computer models now able to generate convincing but fake sounds, photos, and videos, it is valuable to be able to guarantee that a digital file was recorded directly from the physical world. This is a scheme for doing so that uses techniques from public-key cryptography.

The processes of publishing and verifying recordings can be automated in a way that makes them trivial for users without compromising the scheme’s security.

It is possible to use this kind of device to capture a verified recording of some faked input. This is a fundamental problem for any kind of verified recording scheme. For example, an audio recorder might be used to record a computer-generated voice being played through speakers. However, the tamper-proof timestamp and location data make it it challenging to create believable verified fakes in this way.

This scheme requires trusting the manufacturers of recording devices as well as the manufacturing process. These trust assumptions can’t be avoided, and they mean that a sufficiently powerful adversary could subvert the system. However, it is robust enough to facilitate verified recordings in practice.