ONE PERCENT

摘要

Tech-savvy criminals try to evade being tracked by changing their cellphone's built-in ID code and by regularly dumping SIM cards. But Jakob Hasse and colleagues at the Technical University of Dresden, Germany, found that every handset's signal hides within it an unalterable digital fingerprint. Tiny variations in microchip manufacturing processes make each phone generate radio signals with digital errors at unique rates. The researchers are now developing a customised receiver to pick up these signals.