Do metal shields or jackets protect against unauthorized access?

The chip of the e-passport cannot be read if the booklet is placed in a metal jacket. The jacket forms a “Faraday cage” which prevents radio waves from reaching the chip’s antenna. A metal shield, such as a metal insert in a page, is just as effective as it “decouples” the antenna and prevents it from resonating at the frequency of the radio waves.
If the radio waves cannot reach the chip’s antenna and resonate it, then the chip cannot be powered and it cannot communicate.
The myth arises when alternatives to metal are used as shields or jackets. Aluminized plastic is a common alternative, and its thin coating of aluminium does not effectively block strong radio waves.

For more information, visit the Biometric Passeport Tutorial

Courtesy the Keesing Journal, 2009