As Sam mentions, I think this somewhat confuses the concepts of identifier and address. Even in the physical world this is extremely complex. Some set of biographical information often is used as an identifier (name, nationality, DOB, place of birth, parent's details) but this is imperfect as it's often non-unique (one hospital district in Florida has 23 Maria Garcia's with the same DOB as patients), mostly non-revokable, and sometimes changes dependent on context (I'm American when dealing with the US government, British when dealing with the UK, and one/other/both when dealing with other countries). Biometrics likewise have issues with usability (especially remotely) and revocability. Importantly none of these gives anyone a method for communicating with me or for easily asserting my identity. Similarly a 'permanent' address doesn't really exist in the physical world either. Between the ages of 18 and 35, I've lived in 18 locations. In 15 of these my continued presence has been at the whim of the property owners, in the other three I at least theoretically was at risk of compulsory purchase or the mortgage company pulling the rug out from under us. Yes, the legal rights in the physical world are a bit better, but if someone really wants your address they can probably get it. I think with the speed in which internet communication methods (and companies) change, there is no real way we'll ever get a permanent communication channel. What I'd like to aim for is a reliable identifier and a secure directory of the current 'address' for this identifier. Perhaps something akin to a DNS server of public keys and then an email address (or phone/twitter/snapchat) signed by the private key? Lots of challenges in implementation though...