It could work like this: you get the private/public key pair provided in your passport, or on a special social-security-type card. The public key is also on a website registered to your name, so anyone can look up your public key. However, in order to be allowed to sign anything, you have to be in the presence of a government agent who can verify your identity via a second means (e.g., at the DMV, your driver's license + social), and then the government agent signs it as well. So there's no _less_ verification of your identity in the system as before, but anyone can quickly verify the authenticity of your documents.