November 6, 2006

A Contrarian View of Identity — Part 2: Why is this confusing?

This is Part 2 of a multi-part essay on identity. Part 1 can be found here. Part 1 ended with a promise that Part 2 would be up soon, but, as John Lennon once said, life is what happens to you while you’re busy making other plans. But at long last here we are; enjoy.

Part 1 talked, in broad strokes, about the kinds of things that identity gets used for and why, but ended with the assertion that identity is being made to carry a heavier load than it can really support given the character and scope of the Internet. Here I’m going to speculate about why discussion of this seems to generate so much confusion.

One area of confusion is illustrated by a long-standing split among philosophers over the fundamental nature of what an identifier is. They’ve been chewing on the whole question of identity and naming for a long time. In particular, Bertrand Russell and his circle proposed that a name should be regarded as a form of “compact description”, whereas a line of thought promoted by Saul Kripke asserts that names should instead be viewed as “rigid designators”.

The “compact description” point of view should be one that is familiar from the physical world. For example, if you are pulled over for speeding and the police check your driver’s license, they consider whether you resemble the person whose photograph and description are on it. The “rigid designator” perspective is more familiar in the world of computer science, where we use such designators all the time in the form of memory pointers, DNS names, email addresses, URLs, etc.

Without delving into the philosophy-of-language arcana surrounding this debate, you can at least note that these are profoundly different perspectives. While I personally lean towards the view that the “rigid designator” perspective is more fundamental, this is basically a pragmatic position arrived at from my work with object capability systems and the E programming language. In the present discussion you don’t need to have a position yourself on whether either of these positions is right or wrong in some deep, essential sense (or if that’s even a meaningful question). All you need to recognize is that people who come at the identity issue from these different directions may have very different notions about what to do.

Another wellspring of confusion is that different people mean different things when they speak of “identity”. Moreover, many of them seem unaware of or indifferent to the fact that they are talking about different things. While I generally think that the Parable of The Blind Men and The Elephant is way overused, in this case I think it’s a wildly appropriate metaphor. Identity is a complicated concept with a number of different facets. Depending on which facets you focus your attention on, you end up believing different things.

Let’s look at the relationship between two entities, call them Alice and Bob, interacting over the Net. I diagram it like this:

We call them Alice and Bob simply because anthropomorphizing these situations makes them easier to think and talk about. We don’t actually care whether Alice and Bob are people or computers or processes running on computers or websites or whatever. Nor do Alice and Bob both have to be the same kind of thing. All that we care about are that each is some kind of discrete entity with some sense of itself as distinct from other entities out there.

When Alice interacts with Bob, there are (at least) four different distinct acts that are involved, each involving something that somebody somewhere calls “identity”. (1) Bob presents some information about himself, in essence saying “this is me”. (2) Alice, using this information, recognizes Bob, that is, associates the entity she is interacting with with some other information she already knows (remember that we said in Part 1 that relationships are all about repeated interactions over time). (3) Alice, to take action, needs to make reference to Bob. She designates Bob with some information that says, in essence, “that is you”. (4) Bob, based on this information, plus other information he already knows, accepts that Alice is referring to him and provides access to information or services.

At various times, various people have referred to the bundle of information used in one or another of these acts as Bob’s “identity”. However, there are four, potentially different, bundles of bits involved. These bundles can be considered singly or in combination. Depending on which of these bundles your view of things takes into account or not, there are fifteen different combinations that one could plausibly label “identity”. Furthermore, you get different models depending on whether or not you think two or more of these bundles are actually the same bits — the number of possibilities explodes to something like 50 (assuming I’ve done my arithmetic correctly), before you even begin talking about what the rules are. Absent awareness of this multiplicity, it is not surprising that confusion should result.

Observe too that this picture is asymmetrical. Most real interactions between parties will also involve the mirror counterpart of this picture, where Alice does the presenting and accepting and Bob does the recognizing and designating. Note that though the two directions are logical duals, the mechanisms involved in each direction might be radically different. For example, when I interact with my bank’s website, I present a username and password, while the bank presents text, forms, and graphics on a web page.

Those of you of a more technical bent are cautioned to keep in mind that I’m describing an abstract model, not a protocol. In informal discussions of this diagram with techie friends, I’ve noticed a tendency for people to latch onto the details of the handshaking between the parties, when that’s not really the point here.

This model now gives us a way to get a handle on some of the muddles and talking at cross purposes that people have gotten into.

Consider the many people making claims of the flavor, “you own your own identity” (or should own, or should control, or some similar variant of this meme). If you are focused on presentation, this makes a degree of sense, as you are thinking about the question, “what information is Bob revealing to Alice?” If you are concerned with Bob’s privacy (as Bob probably is, let alone what privacy advocates are worried about), this question seems pretty important. In particular, if you adopt the “compact description” stance on names, it seems like this identity thing could be probing pretty deeply into Bob’s private business. On the other hand, if you are focused on recognition, the “you own your own identity” idea can seem both muddled and outrageous. Recognition involves combining the information that was presented with information that you already know; indeed, in the absence of that pre-existing knowledge, the information presented may well be just so much useless noise. From this perspective, a claim that Bob owns his own identity looks a lot like a claim that Bob owns part of the contents of Alice’s mind. It should not come as a big surprise if Alice takes issue with this. Note that this is distinct from a political position which positively asserts that there should be (or believes that there could be) some legal or moral restrictions on what Alice is allowed to know or remember about Bob; there’s an interesting debate there but also a distraction from what I’m talking about.

Note that although the model is explained above in terms of just Alice and Bob, the most interesting questions only emerge in a world where there are more than two actors — if your world only contains one entity besides you, the whole question of the other’s identity is rather moot.

Let’s introduce Carol, a third party, into the picture. Setting aside for a moment discussion of what the identity relationship between Alice and Carol is, consider just the issue of how Bob’s identity is handled by the various parties. Recall that there are four bundles of information in the identity relationship of Bob to Alice:

  • the information that Bob presents to Alice
  • the information that Alice holds, enabling her recognize Bob from his presentation
  • the information that Alice uses to designate Bob
  • the information that Bob holds, enabling him to accept Alice’s designation

What is the scope of this information? Is the information that Bob presents to Alice meaningful only in the context of their particular two-way relationship, or is it meaningful in some broader context that might include other parties? In particular, is the information Bob presents to Alice unique to Alice, or might Bob present himself differently to Carol? If Carol already has a relationship to Bob, do Alice and Carol have the means to know (or to discover) that they are talking about the same Bob? More generally, which, if any, of the above listed four pieces of information does Carol see? Where does she get this information from? From Bob or from Alice or from some third (er, fourth) party?

Similarly, is the information Bob presents to Alice unique to Bob, or might some other entity besides Bob present the same information to her? In the latter case, is she really recognizing Bob or just some abstract Bob-like entity?

Each of these questions, and countless others which I didn’t explicitly raise or perhaps am not even overtly aware of, defines a dimension of the design space for an identity framework. The explosion of possibilities is very large and quite probably beyond the scope of exhaustive, systematic analysis. Instead, it seems more useful to pay attention to the purposes to which an identity system is being put. Any particular design can’t help but embed biases about the ways in which the designers intend it to be used (in and of itself, this is only a problem if the design has pretensions to universality).

I’m not prepared to go into all of these questions here. That’s probably the work of a lifetime in any event. However, there is one very important consideration that I’d like to highlight, which hinges on the distinction between the information that Bob presents to Alice and the information with which Alice designates Bob.

The presentation information seems naturally to fall into the “compact description” camp, whereas the designation information seems to just as naturally fall into the “rigid designator” camp. Indeed, the very language that I’ve adopted to label these pieces contains a bias towards these interpretations, and this is not an accident.

From Bob’s perspective, the information that designates him is far more dangerous than the information he presents. This is because a designator for Bob is the means by which an outside party acts upon Bob. Such action can range from pointing him out to other people in a crowd to sending him email to charging his credit card, depending on the context. Any of these actions might be beneficial or harmful to him, again depending on context, but Bob is fundamentally limited in his ability to control them. Presentation, by contrast, is more clearly under Bob’s control, and the risk posed by presentation information is closely related to the degree to which that information can be reverse engineered into designation information.

Much of the risk entailed by these interactions stems from the fact that in the real world it is rarely Bob himself who does the presenting and accepting; rather it tends to be various intermediaries to whom Bob has delegated these tasks in different contexts. These intermediaries might be technological (such as Bob’s web browser) or institutional (such as Bob’s bank) or an amalgam (such as Bob’s bank’s ATM). Such intermediaries tend to be severely limited in the degree to which they are able to exercise the same discretion Bob would in accepting a designator on Bob’s behalf, partially because they tend to be impersonal, “one size fits all” systems, but mainly because they cannot know everything Bob knows. Analysis is complicated by the fact that they may be able to compensate for some of these limitations by knowing things that Bob can’t. The ubiquitous presence of these intermediaries is a major difference between our modern, online world and the evolutionary environment in which our instincts for these things emerged.

Note that designation is generally associated with specific action. That is, there is usually some particular intent that Alice has in mind when designating Bob, and some specific behavior that will be elicited when Bob accepts the designator. This favors the “rigid designator” perspective: highly specific, with little tolerance nor use for ambiguity. In particular, different designators might be applied to different uses. In contrast, presentation may be open-ended. When Bob presents to Alice, he may have no idea of the use to which she will put this information. The information may, in some contexts, be quite general and possibly entirely ambiguous. This favors the “compact description” perspective.

All of the above leads to the following design prescription: these two bundles of information ought not to be conflated. In particular, Bob most likely will want to exercise much greater control over designation information than over presentation information. In any event, the contexts which these will be used will be different, hence the two should be separate. Furthermore, designation should not be derivable from presentation (derivation in the other direction may or may not be problematic, depending on the use case).

In Part 3 (about whose timing I now know better than to make any prediction), I’ll take a look at some of the more popular identity schemes now being floated, and use this model to hold them up to some critical scrutiny.

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