I agree, it would probably not even be close to foolproof. I believe any implementation of security through acoustic biometrics would be vulnerable to replay a

I agree, it would probably not even be close to foolproof. I believe any implementation of security through acoustic biometrics would be vulnerable to replay attacks. Systems to reproduce acoustics with high fidelity are commonplace - You might be using the output component of such a system right now if you're listening to music. You could make the Assistant remember the exact fingerprints of all previous activation phrases and only trust you if it was original. This could be circumvented if you spoke the activation phrase at any point where your assistant could not hear you, for example to another Assistant of the same brand.