SENDER/EMPFAENGER FUER VERSCHLUESSELTE SIGNALE

A pay program signal is scrambled in an exclusive OR circuiit by a scrambling signal (Ks) derived from a random number generator. The pay program signal is converted into a broadcasting signal by a converter. A transmission information processor alters every month, for example, the contents of an initial value signal applied to the random number generator in order to change a scramble mode. The information processor transmits, via the converter, cipher signal (Ei) for descrambling the pay program signal in, for example, the next month. The cipher signal (Ei1) is stored in a RAM of a subscriber. At this time, a memory area into which the cipher signal (Ei1) is to be stored is designated by a distribution page flag (DP) transmitted from the information processor. The information processor also designates the memory area storing the cipher signal (Ei1), by means of a reference page flag (RF), which is to be used. The key data is used as data to determine a descramble mode of the random number generator.