The PolyCipher Downloadable Conditional Access System provides a new approach to security in cable: a small hardware footprint is used to enable both high security and the flexibility of software downloadable security clients for set-top boxes and other cable-ready devices. An important and often asked question is how much of this system specification should be disclosed publicly? Here we explain the tradeoffs involved in disclosure and motivate the ultimate choice: a combination of public cryptographic primitives embedded in a private defense-in-depth system.