JPH0548672B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an encrypted data receiving device, and particularly relates to a descramble operation when key information for decrypting encrypted data cannot be received. The present invention relates to an encrypted data receiving device that stops.

(Prior Art) In recent years, with the development of new broadcast media, it has become possible to perform telephony tests, still image broadcasts, high-definition television broadcasts, and multi-channel broadcasts using digital signals. With the advancement of such broadcast media, the types of transmission of broadcast programs are becoming more diverse.

Then, on the broadcasting side, charges are made for specific programs, and the transmission signal is agitated, so-called scrambling, to prevent viewers other than the specific subscribers who have signed a contract with the broadcasting station from viewing the program. However, paid broadcasting is performed for contract subscribers, which allows them to view the programs by canceling the scrambling.

In this case, such pay broadcasting is configured with a system as shown in FIG. 2, for example. In Figure 2, the signal targeted for pay broadcasting is transmitted from the transmitting side 10.
0 input terminal IN. This input terminal IN
is connected to one input terminal of a scrambler 10 composed of an exclusive OR, and a random number generated by a random number generator 20 is added to the other input terminal of this scrambler 10, and the input terminal IN is connected to one input terminal of the scrambler 10. , or data such as video is scrambled to obtain a scrambled signal as the output of the scrambler 10.

The random number generator 20 generates random numbers for scrambling the transmission data according to a predetermined sequence using the key data Ki of the transmitting side 100 as an initial value. In order to decrypt the scrambled and encrypted data in this way, it is necessary to transmit some information for descrambling to the receiving side 200. In order to maintain the confidentiality of the transmitted data, the information necessary for the descrambling operation to decrypt the scrambled data is not sent as is, but in the form determined in relation to the password Pi. Data Ei=fi
It is transmitted in the form of (Ki, Pi).

Further, the transmitted data is not always paid program data, and there are cases where it is not necessary to encrypt it by a scrambling operation on the transmitting side 100. In this case, the operation of the random number generator 20 is stopped, the other input terminal of the scrambler 10 is set to "0", and data Fi indicating whether or not scrambling is being performed is sent to the receiving side 200. do. This data Fi and the encrypted key Ei are multiplexed with the scrambled data by a multiplexing circuit 40 via a synthesizer 30 and sent to the receiving side 200.

On the other hand, on the receiving side 200, the separation circuit 21
The data is separated into 0-scrambled data and data to be descrambled. Separation circuit 21
The scrambled received data separated by 0 is applied to one input terminal of a descrambler 220 for decrypting, and this descrambler 22
The output terminal of a random number generator 230 for performing a descrambling operation is connected to the other input terminal of 0.
Since this random number generator 230 generates random numbers in the same sequence as the random number generator 20 on the transmitting side 100, for example, the initial value on the receiving side, the 200 random number generator 230, is the same as the initial value for the random number generator 20 on the transmitting side 100. A value must be given. In this case, the initial value of the random number generator 230 on the receiving side is Ei = fi (Ki, Pi), which calculates Ki from the encrypted key Ei and password Pi sent from the sending side.
It is obtained by combining using the CPU 240.

That is, the key data acquisition circuit 250
The key data separating circuit 260 extracts a synchronization timing signal and the like for separating data from 00, and separates key data Ei and Fi from the transmitting side 100 in a key data separating circuit 260. The separated key data is once written to the RAM 280 via the key data write buffer 270. When it is determined that the data transmitted by data Fi is a scrambled signal by referring to the key data Ei and Fi written in this RAM 280,
The CPU 240 reads the password Pi stored in the ROM 290, and also reads the data Ei from the RAM 280 and converts it into plain text.
is generated in the key regeneration circuit 300 as Ki=g(Pi, Ei). At this time, if the data Fi indicates that the signal is not a scrambled signal, the descrambling operation is stopped, but when the data Fi is not captured, the descrambling operation cannot be stopped even though it should be stopped.

Then, using this data Ki, the initial value of the random number generator 230 is set to be the same as that at the time of scrambling, and the data is decrypted by the descrambler 220.

FIG. 3 is a signal format diagram showing an example of the format of data transmitted from the transmitting side 100. FIG. Bits for synchronization are assigned to . On the receiving side 200, when this header section is detected, importing of the key data is started. Next to this key data, a flag Fi indicating whether the data is scrambled or not is sent. At this time, for example, when all 5 bits are "1", it indicates that the data is encrypted, and when all the bits are "0", it indicates that the data is not encrypted. Note that on the receiving side 200, the above 5.
If three or more bits are "1" among the bits, it is determined to be "1" and the data is identified as being encrypted by scrambling.

Furthermore, after the above-mentioned flak Fi, key information Ki and Ei for descrambling are sent, and then data is sent.

Figure b shows a data format in which data is transmitted without being scrambled, rather than pay broadcasting, and the data is transmitted after the header section Hi and the flag Fi.

(Problem to be Solved by the Invention) However, when pay broadcast data is transmitted in such a data format, if the key information is not captured by the receiving side 200 due to some reason such as transmission distortion, The decryption of the relevant data packet is not performed normally, and the descrambled data of the relevant packet cannot be obtained. In this case, on the receiving side 200, the random number given to the descrambler 220 does not match that on the sending side 100, and even though no key data is obtained, demodulation is performed using the previous key data, so correct data is not demodulated. Such a problem occurs when demodulating pay broadcast data, but a new problem occurs when the broadcast format changes from pay broadcast to free broadcast. In other words, if the key data of the final pay broadcast packet cannot be demodulated when changing from pay broadcast to free broadcast, the descrambler generates a random number based on the previous key data and continues the descramble operation unnecessarily. Descramble operation is performed even after broadcast data arrives. In other words, if the descramble operation continues unnecessarily, there is a problem in that the demodulation operation for unscrambled data is inhibited. Further, when an error occurs in identifying data Fi indicating whether or not transmitted data is a scrambled signal, the scrambling operation may not be stopped and an erroneous descrambling operation may be performed.

This invention has been made in view of the above points, and provides an encryption system that prevents the damage caused by erroneous descrambling by stopping the descrambling operation on the receiving side when missing key information is detected. The purpose of the present invention is to provide a data receiving device.

[Structure of the Invention] (Means for Solving the Problems) An encrypted data receiving device according to the present invention receives encrypted data scrambled based on key data, and
The encrypted data receiving device receives key data for descrambling, and performs descrambling by inputting a signal for descrambling the scrambling to a descrambler in response to the key data, the encrypted data receiving device comprising: a key data capture circuit that captures key data; and a key data capture circuit that determines that the key data has not been captured, and stops supplying the descrambler with a signal to descramble the scrambler. and descrambling operation stopping means, and the descrambling operation is stopped when the key data is not received.

(Operation) In the present invention, scrambled transmission data and key data for descrambling are received. The descrambler receives a signal for descrambling corresponding to the key data and descrambles it. The descramble operation stopping means stops supplying a signal for descrambling corresponding to the key data to the descrambler when the key data is not captured by the key data capture circuit. This prevents descrambling from continuing to malfunction.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of an encrypted data receiving device according to the present invention. FIG. 4 is a circuit diagram showing a specific configuration of the encrypted data receiving device according to the present invention, and parts having functions corresponding to those in the circuit diagram shown in FIG. 2 are designated by the same reference numerals. The explanation will be omitted.

The embodiments shown in FIG. 1 and FIG. By detecting this and stopping the operation of the descrambler, the influence of an erroneous descrambler operation can be prevented.

If proper data demodulation is not performed on the key data transmitted in this manner, it is necessary to stop the descrambling operation in order to prevent erroneous data demodulation of subsequent data.
As mentioned above, this is true not only in the case where a key for descrambling operation is attached to each data packet in the form of paid broadcasting, but also in the case of free broadcasting and paid broadcasting in which no key data is attached in the data packet. This is especially needed in broadcasting systems that change depending on the band. Furthermore, if the identification data Fi indicating the presence or absence of scrambling cannot be obtained, it is necessary to reliably stop the scrambling operation.

In FIG. 3, when the format of the transmitted data shifts from the pay broadcast format shown in FIG. 3a to the non-pay broadcast format shown in FIG. 3b, a key is obtained for the final data packet transmitted in the pay format. If there is no descramble operation, the descramble operation will continue using the key of the previously sent paid data packet, and the unnecessary descramble operation will continue. The disadvantage of this unnecessary descrambling operation is that the descrambling operation continues even though the key for descrambling cannot be obtained. Furthermore, if identification data indicating whether or not a scrambled signal is being transmitted cannot be obtained, it is necessary to provide a function to stop the descrambling operation.

To deal with this problem, in the embodiment shown in FIG. 4, a descramble operation stopping means 310 is interposed between the random number generator 230 and the descrambler 220 constituted by an exclusive OR circuit. The descramble operation stopping means 310 has a key data detecting means 311, and when it is detected that the key data cannot be obtained, the output thereof is set to "0" and the AND circuit 312 is closed.
Therefore, the output of the random number generator 230 is not applied to the descrambler 220, and if key data is not obtained, the descramble operation is stopped. The key data detection means 311 is composed of a counter, for example, and closes the AND circuit 312 when the key data is not obtained within a predetermined time, and prevents the random number from the random number generator 230 from being supplied to the descrambler 220. to stop the descramble operation.

FIG. 5 shows the descramble operation stopping means 3.
10 is a circuit diagram showing an example of the circuit configuration of No. 10, in which the key data detection means 311 is composed of three stages of 4-bit synchronous load type counters C1, C2, and C3. When a data acquisition pulse (negative pulse) is applied from the key data acquisition circuit 250, the counter is set to "3328". In this case, the counter group operates in a low active state. At this point, the counter starts counting the clocks, and if a negative pulse is not obtained from the key data acquisition circuit 250 when the number reaches "1023", the counter starts counting when the number reaches "1023". Stops and outputs a flag of “0” to the carry flag terminal CY. This flag is applied to AND circuit 312 via AND circuit 316, and
12 stops supplying the random number generated by the random number generator 230 to the descrambler 220, and does not perform a descramble operation.

Then, the key data import circuit 250
The descrambling operation continues until the key data is captured and a negative pulse is applied from the key data capture circuit 250 to the descramble stopping means 310.

In this way, when key data is captured and the next key data is not detected within a predetermined time, the key data detecting means 311 determines that the key data that was supposed to arrive has not been obtained, and then The descrambling operation continues to stop until the arrival of key data is detected.

Therefore, if the arrival of key data cannot be detected in the data packet of pay broadcasting shown in FIG. Lift that ban. Furthermore, in FIG. 3, when the transmission data shifts from paid broadcast format data (FIG. 3 a) to a non-paid data transmission format shown in FIG. 3 b,
Since the key data of the final data packet of the pay broadcast data cannot be detected, it is possible to prevent the erroneous descrambling operation from continuing for the next transmitted non-pay data packet.

That is, if the key data cannot be detected, this is detected and the descrambling operation is reliably prohibited, thereby preventing harmful effects caused by an erroneous descrambling operation. Also, data for identifying whether or not the scrambled signal separated by the key data separation circuit 260 is sent to the AND circuit 316.
Even if Fi is not entered properly, the key data Ki
The scrambling operation can be reliably stopped even when the information cannot be identified.

FIG. 6 is a circuit diagram showing another embodiment of the encrypted data receiving device according to the present invention, which differs from the embodiment shown in FIG. 5 in that a comparator is provided in the descramble operation stop means 310. Make it different.

In FIG. 6, the descramble operation stopping means 310 includes a comparator 313 and a key data detecting means 31.
Consists of 4. The key data detection means 314
consists of counters C10, C20, and C30, and is reset when a negative pulse is added to the counter group as a detection pulse upon detection of key data by the key data acquisition circuit 250. Thereafter, the clock pulse applied to the AND circuit 315 is applied to the counter as a clock pulse, and the counter starts counting this clock pulse. At this time, the output of counter C30 “Q0, Q1, Q2, Q
3” is one comparison input terminal “A0,
A1, A2, A3''. This comparator 3
13 other comparison input terminal “B0, B1, B2, B
3" is set to a predetermined number. This set value is at least larger than the arrival period of the key data, and if the key data is still not detected even after reaching this value, It is determined that the key data to be extracted has not been obtained or the key data has not been transmitted.In other words, the count of the counter has progressed, and the value of the key data detecting means 314 is higher than the number B of the comparator 313. Counter output value B
When the value becomes large, the comparator 313 outputs an abnormality flag "0" indicating that there is no key data during the period when the key data should arrive. This abnormality flag is applied to the AND circuit 315, and prohibits the reception of the clock as the count pulse and input to the counter. At the same time, the abnormality flag "0" is applied to the uncircuit 312 via the AND circuit 316, prohibiting random numbers from being added from the random number generator 230 to the descrambler 220 for decryption, and stopping the descramble operation. do.

FIG. 7 is a circuit diagram showing an example of a random number generator 230 applied to the embodiment of the present invention shown in FIGS. 4 to 6 above. Also in this example, if identification data indicating whether or not scrambling is being extracted is not extracted, the scrambling operation can be stopped.

A random number generator 230 shown in FIG. 7 includes a P/S converter 231 for converting parallel data to serial data, a gate circuit 232, a plurality of cascaded D-type flip-flops D1, D2,...Dn, and an exclusive OR circuit 233. It consists of The D-type flip-flop group shifts the data output from the P/S converter 231 every applied clock. This P/S converter 231 includes the key reproducing circuit 30.
Initial data for the random number generator 230 obtained at 0 is obtained. That is, the initial data generated by the key regeneration circuit 300 is generated at the timing of the load pulse LD generated by the timing pulse generation circuit 400 (see FIG. 4) based on the data separation pulse of the key data separation circuit 260. P/S converter 23
1. This initial data is the above P/S
When set to converter 231, gate signal G1 is applied as a negative pulse to gate circuit 232, and initial data is applied to the D-type flip-flop functioning as a shift register. After the initial data is added to this D-type flip-flop, the polarity of the data signal G1 is inverted, and a random number obtained by cycling through the loop path between the D-type flip-flop and the exclusive OR circuit 233 is generated by a random number generator. 230 outputs. A descrambling operation is performed using the random number thus determined.

[Effects of the Invention] As described above, according to the present invention, it is detected that key data for decryption cannot be obtained within a predetermined period at a predetermined timing of each transmitted data packet, and the Thus, the descramble operation can be stopped reliably. This makes it possible to prevent problems caused by erroneous descramble operations.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an outline of the present invention, Fig. 2 is a circuit diagram showing a conventional circuit, Fig. 3 is a data format diagram showing an example of a transmission signal, Figs. 4, 5, and 6. FIG. 7 is a circuit diagram showing an embodiment of the present invention, and FIG. 7 is a circuit diagram showing an example of a random number generator used in the encrypted data receiving apparatus according to the present invention. 230...Random number generator, 250...Key data acquisition circuit, 300...Key regeneration circuit, 310...
Descramble operation stopping means, 311...Key data detection means.

Claims (1)

[Claims] 1. Encrypted data scrambled based on key data and key data for descrambling are received, and a signal for descrambling the scrambling is transmitted to a disk in response to the key data. In an encrypted data receiving device that performs descrambling by inputting data to a rambler, a key data capture circuit that captures the key data and a key data capture circuit that determines that the key data is not captured by the key data capture circuit. , and descramble operation stopping means for stopping supplying the descrambler with a signal for descrambling, and when the key data is not received,
An encrypted data receiving device characterized in that the descrambling operation is stopped.