In order for procedures to be used for personal identification, various requirements must be met: The characteristics may only occur in one person (uniqueness), should occur in as many people as possible (universality), should not change or change only slightly over a period of time (constancy), should be as technically simple as possible (measurability), should be convenient and fast for the user (user-friendliness), and should be practical, as inexpensive as possible, and as little prone to error as possible. To optimize these aspects, it is also possible to combine several methods with different advantages and disadvantages.
However, increased security by means of biometric procedures comes at the expense of convenience, which is accepted in normal everyday life only within certain limits. This is not a new insight either – in 1885, the proposal to protect train tickets from misuse by means of thumbprints was dropped in Cincinnati, as the travelers were not expected to accept it.
Identification options
The idea of using individual identifiers is not entirely new.
- Personal handwriting has long been used as a signature, and more recently as a digital signature; however, the risk of forgery has always been relatively high.
- Dactyloscopy, the process of using fingerprints for identification, has had a firm place in the fight against crime for about 100 years. In China, fingerprints were used to authenticate contracts as early as about the 8th century AD, and in other cultures archaeologists have found stone drawings, clay tablets and vases with fingerprints of even older date. Fingerprints have low false recognition rates.
- Not only the grooves of the fingertips, but also the hand geometry and lines as well as the vein pattern of the back of the hand are used as biometric features (the latter, for example, since 2005 in the German Federal Ministry of Foreign Affairs). So far, the quality of recognition is unclear, especially in the case of changes due to work and aging processes. Further disadvantage is that the hand geometry has quite a lot of similarities in different individuals.
- A measurement of the face (for example, for season ticket holders at the Hanover Zoo) or the iris or retina (Iriscan, Retinascan, for example, frequent flyers at Frankfurt Airport) are other options that are already used. Eye feature determinations are classified as very safe, but are also very costly and are – due to the laser beam used for scanning – only conditionally accepted.
- Light images in ID cards can be automatically compared with the face of the person concerned by means of today’s technology (“machine-readable ID cards”). However, in practice, not enough samples have been studied so far to make a reliable statement about the relationship between image quality and recognition probability.
- In genetic fingerprinting, a person’s DNA is matched with a database maintained by the Federal Criminal Police Office (DNA analysis) and is thus used for identification in criminal proceedings.
In principle, other biometric characteristics are conceivable as a suitable identification feature, but are not yet used. Examples are voice and speech rhythm, body movements, typing behavior on keyboards and body odor.
