The phone can do cryptography, so the signals could be encrypted in appropriate ways. This means that, much as in the case of a genuinely smart identity card, the system will disclose only the minimum information necessary for a transaction to proceed. I could set my phone preferences to present, for example, my works details inside a CHYP certificate when I am in a work setting: shaking hands with someone would lead to an immediate and almost instantaneous bifi transfer, as we exchange contact details and certificates. In a personal setting, I might set the phone to provide different details, different certification. In a nightclub, well, I can only imagine (literally, since I don’t go to nightclubs.
This is yet another layer of technology that cannot deliver on its full potential without an identity infrastructure (or is it metasystem?), because people will need to know and understand how to have control over the disclosure so that they will know what information is being disclosed and in what circumstances. But if we can deliver that infrastructure, technologies such a bifi mean that we will be able to communicate via digital identities in an environment that simultaneously improves both privacy and security (and ease of use, because being able to communicate credentials to a door simply by grasping the handle is going to be even simpler that waving a contactless card).
These opinions are my own (I think) and are presented solely in my capacity as an interested member of the general public [posted with ecto]