SYSTEM FOR PROVIDING TIME DEPENDENT CONDITIONAL ACCESS

摘要

A source transmits (10) successive keys encrypted in encryption control messages and information in an encrypted form that is successively decryptable with the successive keys. A decoder (122) decrypts the information. A secure device (14) receives the encryption control messages, decrypts the keys from the messages and supplies the keys to the decoder (122). The secure device (14) maintains a time value. The secure device (14) controls the supply of the keys dependent on the time value, and increments the time value in response to reception of respective ones of the encryption control messages.