Undermining Homeland Security

"Kerckhoffs's principle applies beyond codes and ciphers to security systems in general: every secret creates a potential failure point. Secrecy, in other words, is a prime cause of brittleness—and therefore something likely to make a system prone to catastrophic collapse. Conversely, openness provides ductility.

[...]Indeed, as a recent National Research Council study points out, the extra security supposedly provided by biometric ID cards will raise the economic incentive to counterfeit or steal them, with potentially disastrous consequences to the victims. "Okay, somebody steals your thumbprint," Schneier says. "Because we've centralized all the functions, the thief can tap your credit, open your medical records, start your car, any number of things. Now what do you do? With a credit card, the bank can issue you a new card with a new number. But this is your thumb—you can't get a new one."

- From The Atlantic