JPS59101988A - Terminal equipment of catv - Google Patents

Abstract

PURPOSE:To reinforce a furtive glance and eavesdropping preventive function by ciphering a key code signal given to a scramble decoder in relation to an intrinsic address signal from an address unit. CONSTITUTION:A scramble decoder which receives an information from the center through a converter 21 sends out a data information to a controller 23. In this case, an intrinsic address signal from an address unit and a ciphered key code from a PROM24 are inputted to the controller 23. The controller 23 operates the key code which is compared with the supplied data information and is ciphered, and the intrinsic address, and supplies a normal key code obtained as its result to a scramble decoder 22. By executing the processing in this way, the furtive glance and eavesdropping function can be reinforced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an 0ATV terminal device equipped with a scramble decoder that decodes a scramble signal from a center using a decryption key code from a controller.

CATV systems are known in which terminal devices are equipped with a scramble decoder system to prevent eavesdropping. For example, as shown in Fig. 1, the scramble decoding system incorporated in this terminal equipment converts a signal sent from the center side to a predetermined frequency, which is a converter 1, inputs it to a scramble decoder 2, and transmits data. The OA TV data transmission signal is distributed to the terminal device demodulator 3, and the signal demodulated by the demodulator 3 is input to the control unit 4. On the other hand, an address signal unique to the terminal device is transmitted from the address unit 5. Enter
It compares it with the transmitted data, performs address verification, determines whether to enable or disable it, and provides a decryption signal to the scramble decoder 1.

Such a scramble decoding system has a very simple configuration and is advantageous when installed in a large number of terminal devices, but the enable signal to the scramble decoder 2 is essentially 1 or 0. , if this part is modified, it will be possible to easily spy on it. Further, since the standard converter 1 is commercially available, and the scramble decoder can also be made by oneself or purchased, prevention of eavesdropping does not have much meaning. In other words, for the purpose of restoring the video signal, the data transmission demodulator 3, control unit 4, and address unit 5 are essentially useless in preventing eavesdropping.

The present invention has been made based on the above circumstances, and is a CATV terminal with a simple configuration, while strengthening the function of preventing eavesdropping and eavesdropping by essentially contributing the function of the control unit to video restoration. The aim is to provide equipment.

The present invention provides an IC for this purpose, which is equipped with a scramble decoder that decodes a scramble signal from a renter using a decryption key code from a controller, and is configured to send data information from the scramble decoder to the controller. At the same time, the controller receives a unique address signal from the address unit and an encrypted key code from the memory.
The device is characterized in that the encrypted key code and the unique address signal are calculated in comparison with the data information, and the resulting regular key code is provided to the scramble decoder. be.

Hereinafter, one embodiment of the present invention will be specifically described with reference to FIGS. 2 and 3. FIG. 2 is a conceptual block diagram of a cryptographic scrambling system. The center-side arithmetic unit 11 receives a signal from a register 12 of a scramble pattern to be superimposed on a video signal, and also receives a signal from a key code register 13. Accepts code signals and performs reversible calculations. The result of this calculation is sent from the scramble code register 14 to the terminal as a scramble code. In the terminal device, the scramble code register 15 similarly accepts this, and the arithmetic unit 16 performs an inverse operation using the key code from the key code register 11 of the terminal device, reproduces a scramble pattern, and sends it out from the scramble pattern register 18. and decode it. The scramble code is transmitted from the encoder on the center side to the decoder on the terminal equipment side by inserting it as digital information into the vertical retrace interval of the video signal in each channel, or into the C-nab channel using a subcarrier. achieve.

In such a scrambling system, in a terminal device, a CATV channel input is converted into a certain predetermined channel by a converter 21 and input to a scramble decoder 22.

This input signal includes digital information in addition to video information, and this information includes the aforementioned scramble code, channel number, and channel tier level. The channel numbers, channel tier levels, etc. are input to the controller 23, and the controller 23 sends key codes corresponding to each channel number, channel tier level, etc. to the scramble decoder 22. In this case, in this terminal device, P
It is equipped with ROM24, and as shown in Figure 4,
A key code corresponding to each channel is encrypted and written. In addition, for channels whose viewing is prohibited, an ice enable code is written instead of a key code to prohibit decoding of said channels. On the other hand, the address unit 25 has a capacity of about 5 or 8 bits, is structurally integrated with the controller 23, and is molded with resin or the like to prevent modification. The contents of this address serve to decode the key code written in the PROM 24. That is, in reality, the key code written in the PROM is not a descrambling code given to the scramble decoder 22, but the key code is formed by calculation with the above address. For example, on the center side, key code register 1
The key code given to 3 corresponds to 1, the result of calculating 2 to the key code of the PROM 24 and the contents of the address using a predetermined operator.

In order to descramble in this way, the PROM in another terminal device is copied and the PROM of the terminal device for the purpose of eavesdropping is copied.
Even if it is replaced with a ROM, the PROM key code will be different for each address, making it impossible to generate a descramble code.

Note that it goes without saying that the greater the number of bits in an address, the higher the security against eavesdropping.

The above PROM also supports battery-supported RA
Replacement with M is also possible.

Further, the converter 21 can be configured separately from the descrambling system by using a commercially available standard converter.

Further, as a preventive measure against eavesdropping, as shown in FIG. 3, in a system in which the converter is a PLL type converter and channels are selected using the keyboard, the number of channels varies depending on the content of the address from the keyboard. Certain user numbers may be manually entered so that when the numbers match, the terminal is enabled. If this number is updated on a long-term basis, it can be effective against theft of the terminal device. In this case, the user number is delivered by mail or the like only to qualified viewers, and the viewer enters the number using a keyboard.

As described in detail above, the present invention uses a key code as a signal that enables scramble decoding, and moreover, the method of writing the 4-knee code is encrypted in relation to the address. Although it is not complicated, it can exhibit far more powerful eavesdropping and listening prevention functions than conventional terminal devices.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a descrambling system in a conventional terminal device, FIG. 2 is a block diagram that does not show the concept of the scrambling system according to an embodiment of the present invention, and FIG. 3 is a block diagram of a descrambling system in a conventional terminal device. FIG. 4 is a block diagram of the descrambling system of the JA station, and is a diagram showing an example of a PROM writing method. 11... Arithmetic unit, 12.13.14.15... Register, 16... Arithmetic unit, 17.18... Register,
21... Converter, 22... Scramble decoder, 23... Controller, 24... PROM, 2
5...Address unit. Figure 1 Figure 33 Figure 4

Claims (1)

[Claims] J3 is equipped with a scramble decoder that decodes the scramble signal from the center using a decryption key code from the controller, and is configured to send data information from the scramble decoder to the controller, and the controller is configured to send the data information from the scramble decoder to the controller. The unique address signal from the unit and the 08-encoded key code from the memory are input, and a regular key code is calculated by comparison with the above data information, and the regular key code signal is given to the scramble decoder. A CATV terminal device characterized by: