This represents a very significant increase in the data trails that people leave behind them, and hence in the privacy-invasiveness of systems. There is a strong likelihood of a public backlash against such schemes, which may take such forms as their outright rejection by consumers, widespread adoption of multiple identities, or rampant obscuration and falsification of personal data.
Smart cards are very flexible instruments, and offer systems designers a great deal of flexibility.
This short paper outlines techniques whereby anonymity and pseudonymity can be achieved. It argues for maximum use of anonymity in schemes, for very careful justification of direct identification, and for maximum use of indirect identification. The presumption is too often made that transactions must be either identified or anonymous. Anonymous schemes, on the other hand, protect the parties' identities, but work against such interests as law enforcement. Pseudonymous' or 'indirectly identified' transactions involve the recording of a pseudo-identifier.