Iris recognition relies upon the fact that every individuals retina has a unique structure. The iris landscape is composed of a corona, crypts, filaments, freckles, pits radial furrows and striatations. Iris scanning is considered a particularly accurate identification technology because the characteristics of the iris do not change during a persons lifetime, and because there are several hundred variables in an iris which can be measured. In addition, iris scanning is fast: it does not take longer than one or two seconds.
These are characteristics which have made iris scanning an attractive technology for high-security applications such as prison surveillance. Iris technology is also used for online identification where it can substitute identification by password. As in other biometric technologies, the use of iris scanning for the protection of privacy is a two-edged sword. The prevention of identity theft applies horizontally but not vertically, i.e. in so far as the data retrieval that accompanies identification and the data body which is created in the process has nothing to do with identity theft.
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Claude Chappe built a fixed optical network between Paris and Lille. Covering a distance of about 240kms, it consisted of fifteen towers with semaphores.
Because this communication system was destined to practical military use, the transmitted messages were encoded. The messages were kept such secretly, even those who transmit them from tower to tower did not capture their meaning, they just transmitted codes they did not understand. Depending on weather conditions, messages could be sent at a speed of 2880 kms/hr at best.
Forerunners of Chappe's optical network are the
For more information on early communication networks see