In information security we've been saddled for years with the tacit assumption that deep down we each have one "true" identity, and that the best way to resolve rights and responsibilities is to render that identity as unique. This "singular identity" paradigm has had a profound and unhelpful influence on security and its sub-disciplines like authentication, PKI, biometrics and federated identity management.
Federated Identity is basically a sort of mash-up of the things that are known about us in different contexts. When describing federated identity, its proponents often point out how drivers licences are presented to boot-strap a new relationship. But it is a category error to abstract this case to as an example of Federated ID, because while a licence might prove your identity when joining a video store, it does not persist in that relationship. Instead the individual is given a new identity: that of a video store member.
A less trivial example is your identity as an employee. When you sign on, HR might sight your driver licence to make sure they get your legal name correct. But thereafter you carry a company ID badge - your identity in that context. You do not present your driver licence to get in the door at work.
Federated Identity posits, often implicitly, that we only really need one identity. The "Identity 2.0" movement properly stresses the multiplicity of our relationships but it usually seeks to hang all relationships off one ID. The beguiling yet utopian OSCON2005 presentation by Dick Hardt shows vividly how many ways there are to be known (although Harte went a step too far when he tried to create a single, albeit fuzzy, uber identity transcending all contexts).
I favor an alternate view - that each of us actually exercises a portfolio of separate identities and that we switch between them in different contexts. This is not an academic distinction; it really makes a big difference where you draw the line on how much you need to know to set a unique identity.
I am an authorised signatory to my company's corporate bank account. I happen to hold my personal bank account at the same institution, and thus I have two different key cards from the same bank. Technically, when I bank on behalf of my company, I exercise a different identity than when I bank for myself, even if I am in the same branch or at the same ATM. There is no "federation" between my corporate and personal identities; it is not even sensible to think in terms of my personal identity "plus" my corporate attributes when I am conducting business banking. After all, so much corporate law concerns separating the identity of a company's people from the company itself. And I think this is more than a technicality too because I truly feel like a different person when I'm conducting Lockstep banking compared to personal banking. I think it's because I am two different people.
Kim Cameron's seminal Laws of Identity deliberately promoted the plurality of identity. Cameron included a fresh definition of digital identity as "a set of claims made by one digital subject about itself or another digital subject". He knew that this relativist definition might be unfamiliar, admitting that it "does not jive with some widely held beliefs - for example that within a given context, identities have to be unique".
That "widely held belief" seems to be a special product of the computer age. Before the advent of "Identity Management", we lived happily in a world of plural identities. Each of us could be by turns a citizen, an employee, a chartered professional, a customer, a bank account holder, a credit cardholder, a patient, a club member, another club official, and so on. It was seemingly only after we started getting computer accounts that it occurred to people to think in terms of one "primary" identity threading a number of secondary roles. Conventional Access Control insists on a singular authentication of who I am, followed by multiple authorisations of what I am entitled to do. This principle was laid down by computer scientists in the 1970s.
The idea that we need to establish a true identity before granting access to particular services is unhelpful to many modern online services. Consider the importance of confidentiality in "apomediation" (where people seek medical information from non technical but "expert" patients) and online psychological counselling. Few will enrol in these important new patient-managed healthcare services if they have to identify themselves before providing an alias. Instead, participants in medical social networking will feel strongly that their avatars' identities in and of themselves are real. Likewise, in virtual worlds and in role playing online games, it's conventional wisdom that participants can adopt distinctly different personae compared to their workaday identities.
Despite the efforts of Kim Cameron and others, and despite the all-too-familiar experience of exercising a range of ids, the singular identity paradigm has proved hard to shake. In defiance of the plurality that features in the Laws of Identity, most federated identity formulations actually reuse identities across totally unrelated contexts, in order to conveniently hang multiple roles off the one identity.
The old paradigm also explains the surprisingly easy acceptance of biometrics. The very idea of biometric authentication plays straight into the world view that each user has one "true" identity. Yet these technologies are deeply problematic; in practice their accuracy is disappointing; worse, in the event a biometric is ever stolen, it's impossible with any of today's solutions to cancel and re-issue the identity. Biometrics' overwhelming intuitive appeal must be based on an idea that what matters in all transactions is the biological person. But it's not. In most real world transactions, the role is all that matters. Only rarely (such as when investigating fraud) do we go to the forensic extreme of knowing the person.
There are grave risks if we insist on the individual being bodily involved in routine transactions. It would make everything intrinsically linked, violating inherently and irreversibly the most fundamental privacy principle: Don't collect personal information when it's not required.
Why are so many people willing to embrace biometrics in spite of their risks and imperfections? It may be because we've been inadvertently seduced by the idea of a single identity.
Great post. A while back, I framed this issue as identity in the cloud faces a unity vs. plurality issue: Identity must live at the point of control, and it must be contingent on a single authoritative source or a trust broker for its validity. I suppose what I was getting at, is that the relying party doesn't care whether there is one identity, just that it can determine whether the asserted one is "right". But, for someone managing the identities, there has to be a "core" identity that can be represented in different ways, depending on the context. The plurality lies in the ability to propagate a consistent set of credentials and associated authorization logic to multiple resources. The unity lies in the ability to centralize the authentication and authorization decisions for multiple external resources from a consolidated point, connected to an authoritative store of record. Since that's the model that vendors can build a sustainable business around, that's where the market has gravitated. Clearly, there is scope for more loosely coupled models, or even implicit authoritative sources that comprise the binding of related set of attributes.