Financial Cryptography describes the alleged mass forgery of identity documents in the US. You can buy a set for $300, but it costs far more than that to get your (genuine) name off the Terrorist Watch list. So, what is identity?
Our society relies more and more on external proof of identity: an ID card, a credit card, driving licence, etc. Show one and you are who it says you are. (This goes to conceptually absurd lengths in UK anti-money laundering practice. Banks are supposed to demand certain documents before they can open an account for you: but they are under no obligation to check that the documents are genuine. So if I show them a passport from an unusual country, they may accept it as proof, even though they cannot know what it should look like.)
Meanwhile, the US and other countries have huge databases of information, used to identify terrorists and criminals, which sometimes go wrong and prevent decent people from boarding aircraft, making financial transactions, etc., because their details resemble those of a terrorist, or because they are the victim of identity fraud – meaning someone stole or forged their documents. According to Financial Cryptography, more than 28,000 people have filed forms to correct such misunderstandings; the US anti-terrorist database holds 400,000 names.
If I can spend your money and hide behind your name, simply by forging documents, smart cards, etc., and linking myself to a set of database entries that should relate to you, where does my identity lie?