Any rational system needs to be able to: 1) Identify someone and 2) Authenticate someone. A moment's thought will suggest that the mechanism used to identify s

Any rational system needs to be able to: 1) Identify someone and 2) Authenticate someone. A moment's thought will suggest that the mechanism used to identify someone has different and at least somewhat conflicting goals to what the mechanism used to authenticate someone has, and these must be different systems. For example: The identification token should be shareable, globally unique, and probably mostly immutable. The authentication token should be secret, not globally unique, and resettable if compromised. The US system currently tries to use SSNs as both a means of identity and authentication: Telling someone your SSN both tells them who you are, and proves that you really are that person. Obviously, this can't work. Either we need an actual unique ID number, and then we treat SSNs as a secret password, OR we need to treat SSNs as non-secret usernames, and add some form of actual authentication. Either will work I suppose, although the second seems more practical.