There are several situations when it would be useful to have a life-long identifier that doesn’t change when we move house, employer or even country. Most of us already have life-long identifiers to link together all our interactions with the health service and the tax office; in research and education linking together our achievements would also be useful when preparing a CV or research proposal. However these applications have very different consequences if the link between individual and identifier fails; they also need to resist different types of threat.
