It uses the “match on card” method, which involves making a fingerprint comparison on the card rather than on the reader (the more conventional method to date).
In traditional biometric systems, templates are stored in a central system along with the identifying information, a fingerprint database.
When a person is requested to prove his identity, a finger has to be scanned and sent to the server. A template is then created and checked against the previously enrolled template.
Match-on-card is an attractive option when the project needs to provide for situations where the identity document will be checked in a non-secured or only partially-secured environment (particularly the verification terminals).
The good news?
Biometric data never leaves the card
Because the data never leaves the card, interception of data during transfer to a reader is impossible.
This solution requires a slightly higher spec card in terms of calculation and memory capacity and OS, than the more conventional storage of fingerprints on card with transfer to terminal for comparison.
Portugal’s history as a former dictatorship and a young democracy (1974), and the population's attachment to public liberties and human rights, put the choice into perspective.