For Passport this is an important number because Stouffer trades as if stock exchanges were going out of style. (Portfolio turnover: 700% a year.) You're not going to have any luck getting this stat from the folks manning the toll-free number.

FORBES: Peekaboo!

"The difference with biometrics and the reason it presents a substantial threat is that if your passport is stolen, the government can reissue you a new passport number and you can move on with your life, " he tells CNN.

CNN: Fully biometric airports becoming a reality

The key turns out to be predictable given that it is sequentially issued and constructed from the passport expiry date, birth date, passport number, and checksum.

ENGADGET: Dutch RFID e-passport cracked -- US next?