Neither. If you want adoption then it needs to be; a parallel option to a password, and more convenient than a password. You don't want to; add more layers to

Neither. If you want adoption then it needs to be; a parallel option to a password, and more convenient than a password. You don't want to; add more layers to a work flow, or implement a system where the user can lock themselves out of their account trying to set up a new authentication process. The people that want to explain why the above is bad security are not representative of the average computer user.