Good question. Yes I think it's more secure if complemented with other good mechanisms. I agree that the current state of most voice based schemes is pretty poo

Good question. Yes I think it's more secure if complemented with other good mechanisms. I agree that the current state of most voice based schemes is pretty poor. But those that involve a separate codebook can be quite tight. Like all things it's more secure in the hands of people moderately educated in protocols and sufficiently sceptical. A general security problem, perhaps a paradox, is that the more we try to hide it for "convenience", the more opaque and automatic, the more people come to blindly depend on the mechanism at some other layer and stop thinking. I suppose what makes voice based interaction more secure is that it's slower. It gives more time for levels of security in depth and for people to figure out something is amiss. But we'll have to see how that pans out with sophisticated voice-spoofing technology because I expect most people, even well educated and sceptical ones, are easily flipped into trust mode by the sound of a seemingly familiar voice and some clever replay attacks.