Passwords are a simple tool for controlling access to computers, networks and online transactions, but wrongdoers can steal or guess them. Fingerprint readers offer greater security, because it is almost impossible to fake a human digit.

Two types of inexpensive readers have proliferated in recent years. Optical scanners, the first technology deployed, use an array of charge-coupled devices to take a digital image of a fingertip. So-called silicon, or solid-state, readers rely on tiny capacitors that sense a fingertip's topography. In both cases, in order to allow or deny access, software analyzes the geometric pattern of minutiae, such as the ridges and valleys that are unique to every finger, and compares it with patterns registered by legitimate users.

This article was originally published with the title No Two Alike.

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