Monday, October 10, 2011

Rethinking authentication

Authentication may end up being the next big thing for mobile devices after the "killer app" that led to us all walking around with them - i.e., voice.  The whole concept of "user authentication" is due for an uplift and all of us effectively becoming net POPs via our mobile devices opens up some interesting possibilities in this area.

Traditionally, authentication is something that punctuates and intrudes on our experience as we do things that only we should be able to do - e.g. access financial accounts, use credit cards, check in to hotels, flights, exclusive events, etc.  A person or automated system gating our access to something has to get to a sufficiently high level of confidence that we are who we say we are in order to let us in.  Authentication puts gates in front of us and we present credentials to get the gates to open.

Having an "always on" POP attached to us allows us to think about the problem differently.  Instead of authenticating at experience-interrupting gates, we can think about continuously updating our estimate of the probability that the person attached to a mobile device is the person who should be attached to that device (call this the right binding probability).  As I walk around and do stuff, take calls, get visually identified, etc., my device can provide a stream of "naturally authenticating information" (eventually based on biometrics, but also including behavioral information as well as the outcome of authentication / identification events).   When I want to do something that only I can do, my authentication state can be pushed in front of me, opening gates and eventually even eliminating most of them altogether in favor of challenges based on thresholds of the right binding probability.

There are obviously privacy considerations to think about here and at the end of the day, it will come down to how much "observation" we are going to allow in order to make authentication more convenient for us and our identities more secure.  Just allowing the phone to identify us via voiceprint and to report this event to an authentication service that we opt in to could provide a convenient second factor for financial transactions - again, without interrupting experience.

Updating right binding probabilities based on authenticating events presents an interesting mathematical modelling problem.  Each event should have an immediate impact, but its effect should decay over time.  A relatively strong event like voiceprint identification should create a significant bump and a weaker event like crossing a geo fence into a common haunt at a regular time should contribute less.  But how, if at all, should the second event affect the decay of the first event's effect?  It seems we need to keep a rolling window of recent events, including their times and an updating algorithm that looks at both existence of event types over backward-looking time intervals as well as sequencing.

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