JP3751055B2 - Broadcast data scrambling and descrambling method and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for scrambling and descrambling broadcast data.
[0002]
[Prior art]
There is known a method for broadcasting text and image data in parallel with audio data using FM multiplex broadcasting or the like. By utilizing this method, for example, in normal FM radio broadcasting, voice information and text and image road traffic information are multiplexed and broadcast, and the road traffic information is received by a traveling vehicle and displayed on the display screen. A new broadcasting service such as playback can be realized.
[0003]
By the way, when such a broadcasting service is performed on a commercial basis, it may be desired to supply data only to customers who have purchased the descrambling device by scrambled and broadcasting the data.
[0004]
Thus, in order to scramble and descramble broadcast data, both the broadcast station and the customer need to use a common scramble key. In addition, the scramble key needs to be changed frequently so that a person other than the customer cannot easily receive the broadcast.
[0005]
One method for realizing this is to broadcast the scrambled key identification information together with the scrambled data from the broadcasting station, and the customer side reproduces the same scramble key from the received identification information and descrambles the received data. It is a method of doing. According to this method, the scramble key can be changed frequently.
[0006]
[Problems to be solved by the invention]
However, since this method requires frequent broadcasting of the scramble key identification information, there is a problem that valuable data packets are consumed for its use.
[0007]
For example, in the case of road traffic information, it is necessary to provide customers with information that changes every moment in real time. Therefore, all the latest road traffic information must be transmitted in a short cycle. Therefore, it is required that the number of data packets per unit time allocated to road traffic information is sufficiently large. However, the number of packets per unit time that can be allocated to text or image broadcasting in FM multiplex broadcasting or the like is not so large as to satisfy the above requirements with a margin. Therefore, if this valuable data packet is consumed by the scramble key identification information, it becomes difficult to provide real-time traffic information even if the consumption is a part of the packets.
[0008]
Accordingly, an object of the present invention is to provide a special scramble key in addition to the net data to be broadcast in a broadcast mode in which data is scrambled and broadcast using a frequently changed scramble key and descrambled on the receiving side. Even if the information is not broadcast, the receiving side can correctly recognize the scramble key and perform descrambling.
[0009]
[Means for Solving the Problems]
According to the present invention, the broadcasting station side extracts a bit string at a predetermined position from the original data packet to be broadcast, generates a scramble key using the bit string, and uses the scramble key to generate the original data packet. Scramble and broadcast. In other words, a part of the original data packet consisting only of data not related to the scramble key is used as scramble key identification information. Therefore, it is not necessary to broadcast special scramble key identification information separately from data to be broadcast. Moreover, since the data content to be broadcast usually changes from moment to moment, the scramble key is automatically changed with the change.
[0010]
On the receiving side, the scrambled data packet is received, a bit string at a position corresponding to the predetermined position is extracted from the data packet, the same scramble key is reproduced using the bit string, and the scramble key is used. Descramble the received data packet.
[0011]
The bit string used as the scramble key identification information can be selected from the original data packet by an arbitrary method. In any case, it is only necessary to make arrangements so that the position of the bit string decided on the broadcasting station side can be recognized on the receiving side.
[0012]
Examples of variations are as follows.
[0013]
(1) The packet may always be selected from a certain position (for example, the head or a position close to the head), or the position may be changed frequently according to the packet number or the like.
[0014]
(2) Some bits arranged continuously in the packet may be selected, or some bits arranged discretely may be selected.
[0015]
(3) The position of the bit string in the original data packet may be rearranged to another position during broadcasting.
[0016]
(4) A bit string selected from a certain packet may be used as scramble key identification information for another packet (for example, a subsequent packet).
[0017]
(5) A bit string selected from a certain packet may be used as common scramble key identification information for a plurality of packets.
[0018]
(6) A set of bits respectively selected from a plurality of packets may be used as scramble key identification information for one packet (for example, the last packet of the plurality of packets, or further subsequent packets).
[0019]
(7) A predetermined fixed value bit string and a bit string selected from the packet may be used selectively or in combination depending on the situation.
[0020]
The bit string used as the scramble key identification information may be broadcast as it is without being scrambled, or may be broadcast after being scrambled by another method. When scrambled, the method must be a method that can be descrambled on the receiving side. For example, one preferred embodiment employs a method of scrambling the scramble key identification information using a specific bit string in a scrambled portion of the original data packet.
[0021]
The method for selecting the specific bit string can have many variations similar to the case of the scramble key identification information. Furthermore, the following variations are possible.
[0022]
(1) The position of each bit of the specific bit string may be fixed or may be changed according to the position of each bit of the scramble key identification information.
[0023]
(2) The specific bit string may be a collection of bits selected from a plurality of positions in the packet, or may be a bit string obtained by repeatedly duplicating and selecting bits selected from one position.
[0024]
(3) The specific bit string may be selected from the packet, or may be a predetermined fixed value.
[0025]
Needless to say, all of the above variations are included in the scope of the gist of the present invention.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIG. 1, one unit of data group 2 handled in an embodiment of the present invention includes a start code 4, a data header 6, actual data 8, and an end code 10. This data group 2 originally does not include information on the scramble key.
[0027]
Here, the start code 4 and the end code 10 declare the start and end of the data group 2 literally. The data header 6 indicates the length (number of bytes) of the actual data 8. The actual data 8 represents net information to be broadcast. For example, it is a set of character and image data representing road traffic information.
[0028]
This data group 2 is divided into a plurality of packets and broadcast. That is, as shown in FIG. 2, the data group 2 is first divided into a plurality of data blocks 14a, 14b, 14c,... Each having a fixed length (for example, 18 bytes) and then input to a scrambler described later. Is done. After that, a fixed length (for example, 4 bytes) prefix 16 is added to each scrambled data block 14 to form each data packet. Here, the prefix 16 includes data block identification, data group number, packet number, and the like. The plurality of data packets configured in this way are broadcast sequentially through the broadcast channel.
[0029]
As shown in FIG. 3, the scrambler for scrambling the data block 14 includes a key number reading unit 20, a master key reading unit 22, a scramble code generation unit 24, and an exclusive OR unit 26. The flow of operation of this scrambler is shown in FIG.
[0030]
As shown in FIG. 4, the key number reading unit 20 selectively reads only the bit bi at the predetermined position i [th] from the input data block 14 (step S2 in FIG. 5). Here, a plurality of values are determined in advance as the position i. Therefore, a plurality of bits (that is, a bit string) are read from the data block 14.
[0031]
The master key reading unit 22 inputs the bit string read by the key number reading unit 20 as a master key number. The master key reading unit 22 has a ROM (not shown) that stores a large number of scrambled master keys (a kind of random numbers prepared in advance) identified by a master key number. The corresponding scramble master key is called from the ROM (step S3 in FIG. 5).
[0032]
The scramble code generator 24 generates a random number sequence by a predetermined algorithm using the called scramble master key as an initial value or a modified value (step S4 in FIG. 5). As specific examples of the scramble master key and the random number generation algorithm, any known one can be adopted, and those skilled in the art have already understood it.
[0033]
The exclusive OR unit 26 scrambles the data block 14 by performing an exclusive OR operation on the random number sequence created by the scramble code generating unit 24 and the input data block 14 (step S5 in FIG. 5).
[0034]
At this time, only the bit string used as the master key number in the data block 14 is not scrambled. This is because, for example, the portion of the random number sequence that is exclusive ORed with the bit string is the exclusive OR of the bit strings, or the exclusive OR unit 26 receives the key number from the key number reading unit 20. This is realized by a configuration in which a control signal works to pass through the bit string.
[0035]
The scrambled data block 14 is broadcast after the prefix 16 is added as described above.
[0036]
When the broadcast receiver receives the broadcast data packet, it first separates the received packet into a data block 14 and a prefix 16 and inputs the data block 14 to the descrambler. The configuration of the descrambler is the same as that of the scrambler shown in FIG. The same applies to the scramble master key and random number generation algorithm in the ROM. The operation flow of the descrambler is shown in FIG.
[0037]
First, the key number reading unit 20 reads a bit bi at a predetermined position i from the received data block as shown in FIG. As already described, bits (bit strings) at a plurality of predetermined positions are read as master key numbers (step S12 in FIG. 6). Since this bit string is not scrambled, the same master key number used by the scrambler is reproduced.
[0038]
Next, the master key reading unit 22 calls a scrambled master key corresponding to the master key number from the ROM (step S13 in FIG. 6), and the scramble code generating unit 24 generates a random number sequence using the master key (step in FIG. 6). S14). In this way, the same random number sequence used by the scrambler is reproduced.
[0039]
Finally, the exclusive OR unit 26 exclusively ORs the random number sequence and the received data block to descramble the received data block (step S15 in FIG. 6).
[0040]
At this time, the bit string used as the master key number in the received data block is not descrambled.
[0041]
In this embodiment, the scrambled and broadcast data group substantially has a configuration as indicated by reference numeral 30 in FIG. Since it is clear that the length of the data group 30 is the same as that of the original data group 2 shown in FIG. 1, the minimum number of packets is the same as that of the original data group 2 being broadcast as it is. Can broadcast. On the other hand, the data group indicated by reference numeral 40 in FIG. 7 is obtained by adding a master key number 50 different from the original data without applying the present invention. As a result, the data length becomes longer, and extra packets are consumed.
[0042]
FIG. 8 shows a slightly complicated configuration of the scrambler and descrambler. That is, a predetermined random number is read from another ROM area 52 and synthesized by the synthesis unit 54 with respect to the scramble master key called from the ROM based on the key number. The scramble code generation unit 24 generates a random number sequence as a scramble code using the numerical value of the synthesis result as an initial value or a modified value.
[0043]
The configuration of FIG. 8 is an example of a slightly complicated scramble and descramble algorithm, but various other complexity and variations are possible.
[0044]
9 and 11 show the configuration of the scrambler and descrambler in the second embodiment of the present invention. In this embodiment, a bit string used as a master key number in a data block is scrambled by another method and broadcasted.
[0045]
As shown in FIG. 9, the scrambler includes an auxiliary number reading unit 60 and a second exclusive OR unit 62 in addition to the configuration shown in FIG. The function of this additional configuration is illustrated in FIG.
[0046]
That is, the auxiliary number reading unit 60 reads the bit bn at the predetermined position n [th] (n ≠ i) from the scrambled data block output from the first exclusive OR unit 26. At this time, as in the case of reading the master key number, the bit bn is read from a plurality of positions to form a bit string as an auxiliary number.
[0047]
The second exclusive OR unit 62 scrambles the master key number by performing an exclusive OR of the auxiliary number from the auxiliary number reading unit 60 and the master key number from the key number reading unit 20. This scrambled master key number is inserted into the position of the master key number of the data block output from the first exclusive OR unit 26 to form the final output data block.
[0048]
Thus, a data block in which all bits are scrambled is output.
[0049]
The descrambler shown in FIG. 11 also includes an auxiliary number reading unit 64 and a second exclusive OR unit 66 in addition to the configuration of FIG. The auxiliary number reading unit 66 reads the same auxiliary number used by the scrambler from a predetermined position n [th] (n ≠ i) in the received data block.
[0050]
The second exclusive OR unit 66 performs an exclusive OR operation on the auxiliary number and the scrambled master key number from the key number reading unit 20 to obtain the same original master key number used by the scrambler. Play. This original master key number is given to the master key reading unit 22 and is also inserted into the output data block from the first exclusive OR unit 26. Thus, the original data block is completely reproduced.
[Brief description of the drawings]
FIG. 1 is a data format diagram showing an original data group handled in an embodiment of the present invention.
FIG. 2 is a data format diagram showing how a data group is divided into data packets in the embodiment.
FIG. 3 is an exemplary block diagram illustrating a configuration of a scrambler and a descrambler according to the embodiment.
FIG. 4 is an explanatory diagram showing a state in which a key number is read from a data block.
FIG. 5 is a flowchart showing the operation of the scrambler of the embodiment.
FIG. 6 is a flowchart showing the operation of the descrambler of the embodiment.
FIG. 7 is an explanatory diagram showing effects of the embodiment.
FIG. 8 is a block diagram showing a configuration when the scrambler and descrambler are slightly complicated in the embodiment;
FIG. 9 is a block diagram showing a configuration of a scrambler in the second embodiment of the present invention.
FIG. 10 is a block diagram illustrating functions of an additional configuration of the scrambler according to the second embodiment.
FIG. 11 is a block diagram showing a configuration of a descrambler according to the second embodiment.
[Explanation of symbols]
14 data block 20 key number reading unit 22 master key reading unit 26 scramble code generating unit 26 exclusive OR unit 60, 64 auxiliary number reading unit 62, 66 second exclusive OR unit

Claims (6)

Key generation means for generating a scramble key given a source data packet and using a bit string at a predetermined position which is a part in the source data packet;
Scrambling means for scrambling the original data packet using the generated scrambling key;
Broadcasting means for broadcasting the scrambled data packet;
Receiving means for receiving the broadcasted data packet;
Key reproducing means for reproducing the scramble key using a bit string at a position corresponding to the predetermined position in the received data packet;
Descrambling means for reproducing the original data packet by descrambling the received data packet using the regenerated scramble key ;
The scramble means scrambles only the part other than the bit string at the predetermined position in the original data packet using the scramble key,
The descrambling means scrambles broadcast data , wherein the descrambling means descrambles only the portion of the received data packet other than the bit string at the corresponding position using the scramble key. And descrambling. The scramble means scrambles the bit string at the predetermined position in the original data packet by another method,
The key reproduction means reproduces the bit string at the predetermined position in the original data packet by descrambling the bit string at the corresponding position in the received data packet by a method corresponding to the other method. Then, the scramble key is reproduced using the reproduced bit string,
Said descrambling means using scramble key said reproduced, the broadcast data according to claim 1, wherein the descrambling portion other than the bit string of the corresponding position of said received data Scramble and descramble method. The scramble means scrambles the original data packet using the scramble key, then scrambles the bit string at the predetermined position using a bit string at a position different from the predetermined position in the scrambled data packet,
The key reproduction means descrambles a bit string at a position corresponding to the predetermined position in the received data packet using a bit string at a position corresponding to the different position in the received data packet; , Reproducing the bit string at the predetermined position in the original data packet, and reproducing the scramble key using the reproduced bit string,
2. The broadcast data according to claim 1 , wherein the descrambling means descrambles a part other than the bit string corresponding to the predetermined position in the received data using the reproduced scramble key. Scramble and descramble method. A broadcast station that scrambles and broadcasts only a part other than the bit string at the predetermined position in the original data packet using a scramble key generated based on a bit string at a predetermined position that is a part in the original data packet , In the receiver used in combination with
Means for receiving the broadcasted data packet;
Key reproducing means for reproducing the scramble key using a bit string at a position corresponding to the predetermined position in the received data packet;
Descramble means for reproducing the original data packet by descrambling only the portion of the received data packet other than the bit string at the corresponding position using the reproduced scramble key. Broadcast data receiver. Wherein a predetermined position the broadcasting station a bit sequence further has a function of scrambling in a different way, in combination with receiver used in the original data packet,
The key reproduction means reproduces the bit string at the predetermined position in the original data packet by descrambling the bit string at the corresponding position in the received data packet by a method corresponding to the other method. Then, the scramble key is reproduced using the reproduced bit string,
5. The broadcast data according to claim 4 , wherein the descrambling means descrambles a portion other than the bit string at the corresponding position in the received data using the reproduced scramble key. Receiving machine. After the original data packet scrambled using the scramble key, from the predetermined position in the scrambled data packet using the bit string of different positions, the broadcast having the function to scramble the bit string of the predetermined position A receiver used in combination with a station,
The key reproduction means descrambles a bit string at a position corresponding to the predetermined position in the received data packet using a bit string at a position corresponding to the different position in the received data packet; , Reproducing the bit string at the predetermined position in the original data packet, and reproducing the scramble key using the reproduced bit string,
Said descrambling means using the scramble key in which the reproduced, according to claim 4, characterized in that said descrambling portions other than the bit string of the position corresponding to the predetermined position of the data the reception Broadcast data receiver.

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