Method and apparatus for constructing a set-top box to protect cryptographic capabilities

摘要

A construction arrangement for a small set-top box to protect cryptographic capabilities and prevent a digital program in clear from being able to be tapped as required by Digital Rights Management protocols. A first layer of sheet metal capable of blocking X-rays, is formed as a shallow pan to hold a set of printed circuit boards. A second layer has a thin epoxy based printed circuit material. A third layer has a printed circuit board with integrated components placed on top of the second layer. A fourth layer has a three layer thin printed circuit board with a first and second metallic layer and holes for large components, such as electrolytic capacitors. A black liquid thermosetting epoxy fills the interstices between the sheet metal layer and the second layer, and between the second layer and the third layer, and between the third layer and the fourth layer, thereby preventing access to exposed circuit trace carrying digital signals in the clear. A connection from the first metallic layer of the fourth printed circuit material layer to a sending circuit and a connection from the second metallic layer so that a short between these two layers sets off an indicator circuit that an attempt is made to enter the protected area.