US Patent 7933410 System and method for a variable key ladder

A method of generating encryption and decryption keys for a multiple tier, variable key ladder (VKL) hierarchy includes determining a device key based on network connection and configuration data contained in conditional access system firmware, decrypting and extracting a session or category key from an input media stream or an Entitlement Management Message using the device key, and configuring a key ladder in response to at least one Entitlement Control Message (ECM), wherein the key ladder comprises the device key and at least one of (i) a program key, (ii) the session or category key, and (iii) at least one control word.