Abstract: A system for controlling access to broadcast transmissions including a transmitter having a transmission encoder for scrambling the broadcast, a multiplicity of subscriber receivers, each having an identical receiving decoder, containing no secret cryptographic keys, for descrambling the broadcast and a plurality of selectable and portable executing apparatus each being operatively associatable with a receiving decoder at a partially different given time and each executing generally identical operations to generate a seed for use by the associated receiving decoder to enable the receiving decoder to descramble the broadcast.