Now that SSNs are used on our driver’s licenses, tax returns, and bank statements, we have the worst of all possible worlds: Numbers that were never intended to be secure are being used to secure our most-valuable information. Because many companies also use Social Security numbers as a password to get into your account, swiping the number from a license or a student ID card gives a person all sorts of access to your life.
One reason that Social Security numbers are so fouled up is that they’re used as both identifiers—a way to keep track of which Joseph Smith you are—and as authenticators—a way for your cell phone carrier to verify that you are, in fact, Joseph Smith when you call to change your plan. Alessandro Acquisti, the lead author on the recent SSN-cracking paper, makes an analogy to phone numbers. Your number, which you’re generally comfortable sharing with friends and colleagues, is a way of identifying you. The PIN number you punch in when you dial in to your voice mail is a way of authenticating that you’re the owner of that number. No rational person, of course, would choose a PIN number that’s the same as their phone number. But that’s the way Social Security numbers work.
The solution proposed in Slate is one that I have often urged, a system of decentralized identification. If you are banking, you should have a bank account number. If go to the library, you should have a library card number. Utility bills, telephone bills, insurance, the list goes on. These context-dependent usernames and passwords enable authentication without the risk of a universal identification system. That way, if one number is compromised, all of the numbers are not spoiled and identity thieves cannot access all of your accounts.