[betterunix]

Yes, every device would need to be able to read smart cards, and everyone would need to have smartcards. Other than the card, everything would just look like normal public key authentication; third parties would not need to store anything other than what they would store if this were done entirely in software.

[addandsubtract]

Then that's not very practical at all.

[betterunix]

Really? We pretty much do it with cell phones right now. You can take a SIM card from one phone, put it into another, and suddenly you are using your cell phone plan with a different phone. This works for billions of cell phones.