JP4990658B2 - Receiver - Google Patents

Description

  The present invention relates to a receiving apparatus that receives encrypted video, audio, or other media data and key information necessary for encryption / decryption.

  As a conventional receiving device, for example, a digital broadcasting receiving device can be cited. The encryption system for digital broadcasting in Japan is defined in ARIB (Association of Radio Industries and Businesses) standard “ARIB STD-B25” relating to the content protection system.

  As defined in these standards, common information (ECM: Entitlement Control Message) is encrypted and transmitted together with media data from the broadcasting station to the receiver, and the common information is decrypted. Individual information (EMM: Entitlement Management Message) is also encrypted and transmitted to the receiver. Therefore, when these ECMs and EMMs cannot be received normally, the media data cannot be decrypted.

  As a recovery method when encryption / decryption cannot be performed normally, for example, as shown in Patent Document 1, decryption is performed normally on the received packet data as a result of decryption by the decryption unit. If it is determined that there is not, there is a method in which the time required for returning to normal decoding processing is shortened by performing return processing. Further, in the receiving apparatus described in Patent Document 1, as a restoration process, a device authentication is performed again with respect to a transmission source to acquire key information again, and decryption is performed using key information that was used immediately before or after. A technique to try is shown.

JP 2000-228059 A

  As described above, the conventional receiving apparatus normally receives key information packets such as ECM and EMM, and performs decryption of media data as long as a key extracted from these key information packets cannot be obtained. Can not. If the reception status of the digital broadcasting radio wave is poor and an error is detected when receiving the key information packet, it is necessary to wait until the next reception timing. Here, the key information packet is normally transmitted periodically, and is transmitted temporally ahead of the media data to be encrypted / decrypted using the key included therein, so that the preceding packet is transmitted. There is no problem if the key information packet can be correctly received at least once within a certain period of time, but there may be a case where acquisition fails continuously in an extremely poor radio wave environment. In some cases, the key information packet cannot be received. In such a case, there is a problem that the time required until the start of encryption / decryption, and finally the waiting time until video / audio reproduction starts, increases for the retransmission period of the key information packet.

  On the other hand, there has been a problem that the restoration process of the receiving apparatus as disclosed in the above-mentioned Patent Document 1 cannot be applied unless there is a mechanism for inquiring the transmission side to acquire key information. In addition, the method that uses the key immediately before and immediately after is adopted a method in which the key changes over time, and the effect can be expected only under extremely limited conditions in which the parameter for controlling the key is incorrect. It is. For example, even in the above digital broadcasting, some key information changes with time, so it is possible to obtain the immediately preceding and immediately following keys, but it is considered very unlikely that encryption and decryption will be successful using them. It was difficult to solve the above problems.

  The present invention has been made to solve the above-described problems, and provides a receiving apparatus that has no waiting time until a key information packet is correctly obtained and can shorten the time required to start encryption / decryption. With the goal.

  A receiving apparatus according to the present invention includes a receiving unit that receives encrypted media data and a key information packet including a key for decrypting the encrypted media data, and a key information packet when the key information packet is an error. A key candidate control unit that extracts key candidates from the key candidate, an encryption / decryption unit that decrypts the encrypted media data using the key candidate, and a determination unit that determines whether or not the decrypted media data is correctly decrypted. The key candidate control unit is configured to determine a key candidate determined to be correctly decrypted by the determination unit as a correct key extracted from the key information packet.

  The receiving device of the present invention does not discard the key information packet containing an error, extracts a key candidate from the packet, attempts to use it for encryption / decryption, and if it is determined that the decryption has been successful as a result, Since the key candidate is used as a normal key, there is no waiting time until a key information packet is correctly obtained, and the time required to start encryption / decryption can be shortened.

Embodiment 1 FIG.
1 is a block diagram showing a receiving apparatus according to Embodiment 1 of the present invention.
In the figure, the receiving apparatus includes a receiving unit 10, an encryption / decryption unit 11, a key control unit 12, a key candidate control unit 13, and a determination unit 14.
The receiving unit 10 is a functional unit that receives media packets such as encrypted video and audio, and key information packets including key information necessary for decrypting them from a transmission path (not shown). The encryption / decryption unit 11 receives the encrypted packet received by the reception unit 10 and decrypts the encrypted packet based on the key or key candidate output from the key control unit 12 or the key candidate control unit 13 It is. The key control unit 12 is a functional unit that performs key generation processing from a normal (error-free) key information packet output from the reception unit 10 and outputs the generated key information packet to the encryption / decryption unit 11. The key candidate control unit 13 This is a functional unit that generates a key candidate from an errored key information packet output from the receiving unit 10 and outputs the key candidate to the encryption / decryption unit 11. The determination unit 14 is a functional unit that determines whether or not the decrypted packet decrypted by the encryption / decryption unit 11 is correctly decrypted, and is configured to output the determination result to the key candidate control unit 13. ing.

Next, prior to describing the operation of the receiving apparatus according to the first embodiment, generation of key information will be described with reference to FIG.
The configuration shown in FIG. 2 is defined by the above-mentioned standard “ARIB STD-B25”. Media data (program content) such as video and audio distributed from the broadcasting station 100 is encrypted and transmitted by a predetermined method, and the key at that time is called Ks (scramble key). This Ks is encrypted with another key Kw (work key) and transmitted as an ECM which is a part of the control data. Further, this Kw is encrypted with a key called Kd (device key) and transmitted as EMM which is a part of the control data.

  Media data, ECM, and EMM are transmitted together, whereas Kd is configured to be commonly held by the broadcasting station 100 and the receiver 200. The receiver 200 first receives ECM and EMM, acquires Kw using Kd held by itself, and further acquires Ks using Kw, thereby performing encryption / decryption of desired media data. Is possible.

The present invention relates to the configuration of the receiver 200 as described above, and the operation of the receiving apparatus according to the first embodiment will be described below.
An encrypted media packet such as video and audio and a key information packet including key information necessary for decrypting them are input from the transmission path to the receiving unit 10. The encrypted packet is input to the encryption / decryption unit 11, and the key information packet is input to the key control unit 12 when there is no error, and is input to the key candidate control unit 13 when there is an error. In the encryption / decryption unit 11, the encrypted packet input from the reception unit 10 is encrypted and decrypted in units of packets with the key acquired from the key control unit 12 or the key candidate input from the key candidate control unit 13. The data is output to the determination unit 14 or a media decoding unit (not shown) in the subsequent stage. For example, when media data is encoded, the media decoding or the like is performed. The key control unit 12 analyzes the error-free key information packet received from the receiving unit 10, extracts the key, and notifies the encryption / decryption unit 11. On the other hand, the key candidate control unit 13 analyzes the error key information packet received from the receiving unit 10, extracts key candidates, and notifies the encryption / decryption unit 11. The determination unit 14 analyzes the encrypted / decrypted packet and notifies the key candidate control unit 13 of a determination result as to whether or not the decryption has been normally performed.

  First, the operation in the normal case, that is, when the key information packet is normally received will be described. When the reception unit 10 receives the key information packet, it notifies the key control unit 12 where the key is extracted and the key is set in the encryption / decryption unit 11. The encryption / decryption unit 11 performs encryption / decryption of the encrypted packet from the reception unit 10 using the key, and outputs it to the subsequent stage. In the case of data such as video and audio, media decoding processing is performed in the subsequent stage, and is displayed and reproduced. If the media data is unencoded data such as character information (text), it is output as it is. When the key changes periodically, the key control unit 12 extracts the key from the key information packet and sets it in the encryption / decryption unit 11 each time.

  Next, the operation when there is an error in the key information packet will be described. When the receiving unit 10 receives a key information packet with an error, it notifies the key candidate control unit 13. The key information packet only knows that there is an error, and it is completely unknown which parameter is correct. Therefore, the key candidate control unit 13 performs analysis by assuming that each parameter including each PID (packet ID) is correct, and cannot determine whether the key obtained as a result is the correct key at this time. Treat as a candidate. This key candidate is set in the encryption / decryption unit 11 and an attempt is made to actually decrypt the encrypted packet. At this time, the decoding result is not output to the subsequent stage, but is output only to the determination unit 14. The determination unit 14 determines whether the decryption has been correctly performed, and notifies the key candidate control unit 13 of the result. When the key candidate control unit 13 receives the normal decryption determination result, the key candidate control unit 13 determines that the key candidate is the correct key and continues to notify the encryption / decryption unit 11. The encryption / decryption unit 11 decrypts to the subsequent stage. Start outputting finished packets. On the other hand, if a determination result indicating that decryption has not been correctly performed is received, the notification of the key candidate is stopped and the process waits until reception of the next key information packet.

  The reception process of the encrypted packet and the key information packet is performed as follows. For example, when the data to be transmitted is in the MPEG2-TS format conforming to the international standard MPEG2 Systems (ISO / IEC 13818-1), the receiving unit 10 analyzes the header of a TS packet having a fixed length of 188 bytes, which is the minimum transmission unit, The aforementioned processing can be realized. Note that the header is not encrypted.

First, the receiving unit 10 refers to the PID area to identify the key information packet and the media packet. The PID is assigned for each packet type, and the key information packet can be detected and distributed by this PID. Although the PID of the key information packet may be fixed, it is generally obtained by analyzing a control packet of another fixed PID.
Also, the presence / absence of encryption can be determined by transport_scramble_control, which is flag information of the TS header, and the presence / absence of an error can be determined by transport_error_indicator.

As an example of the configuration of the key information packet, the ECM configuration in the above-mentioned Japanese digital broadcasting standard will be described.
FIG. 3 is an explanatory diagram showing the relationship between the key information packet, the ECM, and the scramble key Ks.
The ECM is configured in a format called a section defined in the standard MPEG2 Systems, with a section header at the beginning and CRC at the end. In this example, it is contained in one TS packet and the remainder is padded, but one section may be divided into a plurality of TS packets and transmitted. Like the PID of the TS packet, the ECM section is assigned an ID called table_id, and can be identified by the ID. Since Ks is stored at the specified position of the ECM section, Ks can be easily obtained by analyzing according to the format from the head of the ECM section.

  In the Japanese digital broadcasting standard, a block encryption method called MULTI2 is adopted as a scramble method for media data. It is encrypted in units of TS packets with 8 bytes of Ks.

  Next, the determination operation in the determination unit 14 will be described. The determination unit 14 determines whether or not the decryption result is correct for the packet decrypted with the key candidate. Specifically, here, as in the detection determination unit in the receiving apparatus of Patent Document 1, determination is performed based on whether or not a specified pattern exists at a specified position according to the type of media data. Patent Document 1 shows a specific pattern or the like in the DV format as an example of the prescribed pattern. In addition, for example, in the case of the MPEG2 Video format (ISO / IEC 13818-2), a picture header (4 bytes of 00000100h), etc. May be used. Furthermore, since the slice header appears at a relatively high frequency in the form of 00000101h and 00000102h, the fourth byte is incremented by one, it can be said that the slice header is easy to use. On the other hand, the synchronization byte at the head of the TS packet listed in Patent Document 1 cannot be used because it is a part that is not subject to encryption in the case of digital broadcasting.

In the first embodiment, the key control unit 12 and the key candidate control unit 13 are independent blocks, but these functions may be provided in the reception unit 10 and may be collectively performed by the reception unit 10.
Further, although digital broadcasting has been described as an example, it may be used for satellite communication or other encrypted data communication, and the transmission format may not be MPEG2-TS. Further, for example, even when a retransmission request of a key information packet is possible to the transmission source, if a correct key can be obtained from an erroneous key information packet as shown in the present embodiment, There is no need to make all retransmission requests. Only when a correct key cannot be obtained, a method of making a retransmission request is conceivable.

  As described above, according to the receiving apparatus of the first embodiment, the reception unit that receives the encrypted media data and the key information packet including the key for decrypting the encrypted media data, and the reception unit receive the encrypted media data. A key candidate control unit that extracts key candidates from the key information packet, and an encryption / decryption unit that decrypts encrypted media data using the key candidates extracted by the key candidate control unit, A determination unit that determines whether or not the media data decrypted by the encryption / decryption unit is correctly decrypted, and the key candidate control unit extracts a key candidate that is determined to be decrypted correctly by the determination unit from the key information packet Since it is determined as the correct key to be extracted, when a key information packet with an error is received, a key candidate is extracted from the packet to check whether it is the correct key, and when the key is determined to be correct Since the encryption and decryption is immediately started using the key, there is no need to wait until the next key information packet is received. Thus, even in a reception environment with many errors, the decryption is started and the media data is reproduced thereafter. The waiting time can be shortened.

Embodiment 2. FIG.
In the first embodiment, as a key candidate extraction method in the key candidate control unit, an error key control packet is considered to be analyzed without any error. However, in the second embodiment, a key candidate different from this is analyzed. The extraction method of will be described.

FIG. 4 illustrates a specific example of a key storage position in a section including key information and a key extraction method when the section is normally received.
FIG. 5 is an explanatory diagram showing a method for extracting key candidates when the same section as FIG. 4 is received in an error state. That is, in these examples, the key candidate control unit 13 is configured to detect a fixed pattern around the key candidate and extract the key candidate based on the relative position of the fixed pattern.

  The key information storage position in FIG. 4 shows a case where there are a plurality of variable areas between the head of the section and the key storage position. In general, such a variable area has a fixed pattern similar to the above-mentioned PID and table_id and pointer (length) information indicating the end of the variable area (the start of the next area) at the head part. Reach the key storage location. In the example of FIG. 4, the pointer information is sought twice from the beginning, and the key storage position is reached. That is, first, the fixed pattern B is obtained according to the pointer information of the fixed pattern A, and then the fixed pattern C near the key storage position is reached according to the pointer information of the fixed pattern B.

  Next, the example shown in FIG. 5 has the same structure as that shown in FIG. 4, but shows a case where key candidates are extracted from a section with an error. As shown in the first embodiment, there is no parameter that is guaranteed to be correct for erroneous data. Therefore, unlike the case of FIG. 4, without using pointer information, a fixed pattern C in the vicinity of the key storage position is directly searched to determine the key storage position, and a key candidate is extracted therefrom.

Here, another key candidate extraction method will be described.
FIG. 6 is a block diagram showing a receiving apparatus for realizing the key candidate extraction method. The difference from the first embodiment shown in FIG. 1 is that key storage location information is notified from the key control unit 12 to the key candidate control unit 13a. The key candidate control unit 13a is configured to extract a key candidate from the key information packet having an error based on the key storage position information notified from the key control unit 12.

  Next, another key candidate extraction method by the receiving apparatus shown in FIG. 6 will be described. In this method, the key candidate control unit 13a uses the key storage position information from the key control unit 12. When the key control unit 12 receives an error-free key information packet and extracts a key therefrom, the key control unit 12 notifies the key candidate control unit 13a of key storage position information from which the key has been extracted. Specifically, the key storage position information is, for example, the number of bytes from the beginning of the section. If a section is divided into a plurality of TS packets and transmitted, the number of packets from the head of the TS packets constituting the section and the number of bytes from the head of the packet are listed.

  The key candidate control unit 13a that has been notified of the key storage location information as described above does not analyze the packet when the error key information packet is input, but the data obtained from the location indicated by the key storage location information. Are extracted as key candidates.

  By the way, when one or both of the two types of key candidate extraction methods shown in the second embodiment are used, a case where a plurality of key candidates can be obtained from one key information packet is assumed. For example, in the method shown in FIG. 5, it is assumed that a plurality of fixed patterns are found. In the method shown in FIG. 6, when the key storage position in the key information packet is not fixed, the key storage position information notified from the key control unit 12 is not always the same value.

FIG. 7 shows an operation flowchart of the key information control unit 13 (13a) in the second embodiment until a correct key is specified when a plurality of key candidates are extracted in this way. Hereinafter, this flowchart will be described.
First, when a key information packet with an error is input to the receiving unit 10 (step ST100), the key candidate control unit 13 (13a) extracts a key candidate (step ST101) and notifies the encryption / decryption unit 11 of it. (Step ST102). Next, the determination unit 14 is notified of the determination result as to whether the encryption / decryption has been normally performed using the key candidate (step ST103). In the determination result (step ST104), if the decryption is successful, the key candidate control unit 13 (13a) determines that the key candidate is the correct key (step ST104), and starts outputting the decryption result by the encryption / decryption unit 11 to the subsequent stage. (Step ST105). If decryption fails, the key candidate is determined to be an invalid key (step ST104). Here, in the key candidate control unit 13 (13a), when another key candidate exists, the key candidate is notified again to the encryption / decryption unit 11 (steps ST106 and ST102). If there is no other key candidate, it is determined that a normal key cannot be acquired from the key information packet with an error input this time, and the process waits until the next key information packet is input (step ST107).

  Note that one of the key candidate extraction methods may be selected from the methods shown in the present embodiment and the first embodiment, or a plurality or all of them may be used in combination.

  As described above, according to the receiving apparatus of the second embodiment, the key candidate control unit detects the fixed pattern around the key candidate and extracts the key candidate based on the relative position of the fixed pattern. Even if there is an error in the parameter before the fixed pattern, the key candidate can be extracted without being affected by the error.

  Further, according to the receiving apparatus of the second embodiment, the key control unit includes a key control unit that extracts a key from the error-free key information packet received by the receiving unit and sends the key to the encryption / decryption unit. The key candidate control unit is notified of a key storage position in an error-free key information packet received in the past, and the key candidate control unit extracts a key candidate from an error key information packet based on the key storage position. As a result, if the key storage position does not change, key candidates can be extracted without being affected even if there are errors in other parameters.

  Further, according to the receiving apparatus of the second embodiment, when there are a plurality of key candidates, the key candidate control unit selects all the key candidates from among the plurality of key candidates unless it is determined that the determination unit correctly decrypts the key candidates. Since the encryption / decryption unit is provided, the probability of obtaining a correct key from the key candidates can be increased.

Embodiment 3 FIG.
In the first and second embodiments, key candidate extraction from a key information packet having a key used for decrypting media data (this is referred to as a first key) has been described. In the present embodiment, these key information When the packet is further encrypted with another key (this is referred to as a second key) and transmitted in the second key information packet that transmits the second key, the key candidate and the second key candidate A method of extracting and determining a correct key will be described.

  FIG. 8 is a diagram for explaining a specific example of key candidate extraction in a double key structure. FIG. 9 shows a block configuration of a receiving apparatus for realizing key candidate extraction as shown in FIG. ing. FIG. 10 is a diagram for explaining a processing flow when the key extraction of FIG. 8 is performed in the block configuration of FIG.

  First, FIG. 8 will be described. Assume that Ks, Kw, ECM, and EMM in this figure maintain the relationship shown in FIG. That is, Kw (second key) is obtained from the EMM, the ECM is decrypted with the Kw, Ks (first key) is extracted, and the media packet is decrypted with Ks. Actually, EMM also requires encryption / decryption with Kd. However, since there is no key candidate for Kd held inside, description thereof is omitted here.

  FIG. 8 shows a case where an EMM with an error is first received, and two key candidates Kw candidate 1 and Kw candidate 2 are obtained. Next, encryption / decryption is performed on the ECM without error using these key candidates. It is assumed that Ks candidate 1 is acquired using Kw candidate 1 and Ks candidate 2 is acquired using Kw candidate 2. Here, the media data is decrypted using these two key candidates Ks candidate 1 and Ks candidate 2, and the key candidate is correct from the presence or absence of the specific pattern as described in the first and second embodiments. Determine whether or not. In FIG. 8, since a specific pattern is detected when Ks candidate 2 is used, it is determined that Ks candidate 2 is the correct key Ks2. Further, as a result, the Kw candidate 2 used to generate the Ks candidate 2 can also be determined as the correct key Kw2.

  Next, FIGS. 9 and 10 will be described. 9 is different from the first embodiment shown in FIG. 1 in that a decrypted key information packet is input from the encryption / decryption unit 11 to the key candidate control unit 13b. Further, the key candidate control unit 13b is configured such that the first key information packet for generating the first key is encrypted with the second key, and the second key information for generating the second key. If the packet is an error, the second key candidate is extracted from the second key information packet, and the first key obtained as a result of decrypting the first key information packet using the second key candidate is The media data is decrypted by using the data, and when the determination unit 14 determines that the decryption has been normally performed, the first and second keys are determined to be correct.

Hereinafter, how the processing shown in FIG. 8 is realized in the receiving apparatus of FIG. 9 will be described with reference to FIG.
An error key information packet, EMM, is input from the receiving unit 10 to the key information control unit 13 (step ST200). Next, key candidates Kw candidate 1 and Kw candidate 2 which are second key candidates are extracted from this EMM, and Kw candidate 1 is first input to the encryption processing unit 11 (step ST201). On the other hand, since the ECM which is the encrypted key information is input to the encryption processing unit 11 (step ST202), this encryption / decryption is performed. Normally, the encryption of the key information packet is different from the encryption method of the media packet, and the encryption range is not the entire TS packet but only a specific area. The decrypted ECM is input to the key candidate control unit 13b (step ST203). Even if there is no error in the originally received ECM itself, it is decrypted with the key candidate Kw candidate 1, and the validity of the result is not guaranteed, so here the key candidate control unit 13b, not the key control unit 12 is used. Is entered.

  Next, from this ECM, the key candidate Ks candidate 1 which is the first key candidate is extracted, notified to the encryption processing unit 11 (step ST204), and the encryption processing unit 11 decrypts the media packet (step ST205). Then, the determination unit 14 determines whether the encryption / decryption result is normal (steps ST206 and ST207). In the example of FIG. 8, since the result is NG, as described above, another key candidate Kw candidate 2 extracted from the EMM having an error is input to the encryption processing unit 11 as in step ST201 (step ST211). Thereafter, the same operation as in steps ST202 to ST206 is repeated. However, this time, the determination result in the determination unit 14 is determined to be normal (step ST217), and as a result, the Ks candidate 2 is determined to be the correct key. Accordingly, Kw candidate 2 used for Ks candidate 2 extraction is also determined as a correct key, and is applied to subsequent encryption / decryption.

In the description of FIG. 8, two key candidates are extracted from the EMM, but the number is not limited to this.
9 is expanded based on the second embodiment, but may be a receiving apparatus that does not have an input signal from the key control unit 12 to the key candidate control unit 13 as in the first embodiment. .
In addition to the media packet, the encryption / decryption unit 11 performs encryption / decryption of the key information packet. However, the key control unit 12 and the key candidate control unit 13 may be provided with such a function.
In addition, although it has been determined that the encryption / decryption result of the ECM alone cannot determine whether or not the encryption / decryption has succeeded, it is determined whether or not a specific pattern exists in the result of the ECM / decryption as in the case of the media data, and the media data is not decrypted. It may be determined whether the Kw key candidate is normal.
Further, even when multiple encryption is performed using the third and fourth keys, the same procedure may be repeated.

  As described above, according to the receiving apparatus of the third embodiment, the key candidate control unit uses the other key to encrypt the key information packet for generating the key, and generates the other key. When another key information packet is an error, another key candidate is extracted from the other key information packet, and the key obtained as a result of decrypting the key information packet using the other key candidate is used to store the media data. When the decryption is performed and it is determined by the determination unit that the decryption has been successfully performed, the key and the other key are determined to be correct. Therefore, it is possible to receive encrypted communication having a double key structure. If another key that encrypts the key is transmitted with a longer retransmission cycle than the key that encrypts the media data, the re-transmission / reception waiting time when receiving an error is greatly reduced. can do.

Embodiment 4 FIG.
In the first, second, and third embodiments, the unique pattern of the media data after the encryption / decryption is used to determine whether or not the result of the encryption / decryption of the media data is successful. This will be described as 4.

  FIG. 11 is a block diagram illustrating a receiving apparatus according to the fourth embodiment. The difference from the configuration of FIG. 1 is that a media decryption unit 15 is provided at the subsequent stage of the encryption / decryption unit 11, while the determination unit 14 in FIG. 1 is lost and an input signal to the key candidate control unit 13 c is determined by the determination result from the determination unit. Instead, the error detection result from the media decoding unit 15 is used. That is, the key candidate control unit 13c is configured to determine that the key candidate is correct when the decryption result in the media decrypting unit 15 is not an error. Here, the media decryption unit 15 is a functional unit that decrypts the media data encrypted and decrypted by the encryption / decryption unit 11.

Next, the operation of the receiving apparatus according to the fourth embodiment will be described.
First, the process is the same as in the previous embodiments until encryption / decryption is attempted using a key candidate extracted from the key information packet. Next, the decrypted packet is input to the media decrypting unit 15 as it is. The media decrypting unit 15 decrypts the media data. For example, when the encrypted / decrypted packet is encoded data, the encoded data is decoded. Here, if the preceding encryption / decryption fails, the media data does not form a predetermined format, so the decryption of the media data fails, an error is detected, and the error detection result is the key candidate control unit 13c. Is output. If this error detection is not performed, the key candidate control unit 13c determines that the encryption / decryption result is normally performed and determines that the used key candidate is the correct key. On the other hand, when the error detection is notified, the notification of the key candidate is stopped and the same as when receiving the error detection notification in any of the embodiments, such as waiting until the next key information packet is received. Process.

  It is not a problem of encryption / decryption, but the received media data packet itself has an error and the media decryption unit 15 may detect an error. Therefore, what kind of error notification is sent to the key candidate control unit 13c? A certain condition may be set such that the error is detected how many times.

In FIG. 11, only one block is shown as the media decoding unit 15, but a plurality of media decoding units may exist depending on the media type.
11 is based on the configuration of FIG. 1 of the first embodiment, but may be based on the configuration of another embodiment.

  As described above, according to the receiving apparatus of the fourth embodiment, the media data decrypted by the encryption / decryption unit using the key candidate is input, the input media data is decrypted, and whether or not the decryption result is an error. And the key candidate control unit determines that the key candidate is correct when the decryption result in the media decryption unit is not an error, so the block for determining the decryption result is omitted. Can lead to a reduction in hardware or software resources. Even when the specific pattern does not exist, or even if it exists, the appearance period is long, or the pattern is complicated, it can be determined whether the decoding result is normal.

Embodiment 5 FIG.
In each of the above embodiments, when the key candidate is successfully decrypted, the key candidate is regarded as correct and data is output to the subsequent stage. However, in Embodiment 5, the key information packet is correctly received. A configuration that waits until this is done will be described.

  FIG. 12 is a block diagram illustrating a receiving apparatus according to the fifth embodiment. The difference from the configuration of FIG. 1 is that a media decryption unit 15 and an output control unit 16 are added to the output destination of the decrypted packet, and a key is further output from the key control unit 12 to the key candidate control unit 13d. In addition, a mute control signal is output from the key candidate control unit 13d to the output control unit 16. Here, the media decryption unit 15 is a functional unit that decrypts the media data encrypted and decrypted by the encryption / decryption unit 11 in the same manner as the media decryption unit 15 of the fifth embodiment. In addition, the key candidate control unit 13d determines that the key candidate determined to be a correct key matches the key extracted from the error-free key information packet notified from the key control unit 12 thereafter, to the output control unit 16 It is configured to instruct output permission. Further, the output control unit 16 is configured to determine whether or not to output the data decrypted by the media decryption unit 15 to the outside according to an instruction from the key candidate control unit 13d.

Next, the operation of the receiving apparatus according to the fifth embodiment will be described.
The process until the key candidate control unit 13d determines that the key candidate is the correct key and outputs a decrypted packet in the subsequent stage is the same as in the previous embodiments. However, depending on the specifications of the receiving device, from the viewpoint of security, it may be considered that the received data cannot be output to the outside of the receiving device in a situation where the correct key is not received. Therefore, when the key candidate control unit 13d determines that the key is correct, the media decryption unit 15 performs media decryption so that the output control unit 16 is not output after the output control unit by the mute control signal. Give instructions.

  Thereafter, the key control unit 12 receives an error-free key information packet, extracts the key, notifies the key candidate control unit 13d, and compares the key candidate determined to be correct with the key candidate control unit 13d. Do. If they match, the output control unit 16 is instructed to cancel mute and output to the outside of the receiving apparatus. For example, in the case of a digital broadcast receiver, video display, audio reproduction, input to a storage device, and the like are performed.

  It should be noted that the key control unit 12 may perform the comparison of the normally received key and the key determined to be correct among the key candidates and the mute control to the output control unit 16, or two keys may be used. It may be sent to the output control unit 16 and the output control unit 16 itself may perform mute control.

  As described above, according to the receiving apparatus of the fifth embodiment, the media decrypting unit that inputs the media data encrypted and decrypted with the key candidate that the key candidate control unit determines to be the correct key, and decrypts the media data; An output control unit that determines whether or not to output the data decrypted by the media decryption unit to the outside in response to an instruction from the key candidate control unit, the key candidate control unit, After that, when the key extracted from the error-free key information packet matches, the output control unit is instructed to permit output. For example, output to the outside without receiving the correct key It is possible to deal with standards that are not allowed. In addition, since the decryption and the decryption of the media have been completed with the key extracted from the key candidates, it is possible to output the received data to the outside with a shorter delay time than performing the processing after receiving the correct key. It becomes possible.

  Note that the block configurations of the receiving apparatuses described in the first to fifth embodiments are not necessarily realized by hardware, and some or all of the functions may be implemented as software. For example, when configured by software, the receiving device of the present invention is realized by a computer, and the receiving unit 10 to the output control unit 16 include software corresponding to some or all of the functions, and for executing these software. It can be configured by hardware such as a CPU and a memory.

It is a block diagram which shows the receiver by Embodiment 1 of this invention. It is explanatory drawing which shows the production | generation operation | movement of the key information which concerns on the receiver of this invention. It is explanatory drawing shown about the relationship between the key information packet of the receiver by Embodiment 1 of this invention, ECM, and the scramble key Ks. It is explanatory drawing which shows an example of the key extraction method of the receiver by Embodiment 2 of this invention. It is explanatory drawing which shows the other example of the key extraction method of the receiver by Embodiment 2 of this invention. It is a block diagram which shows the further another example of the receiver by Embodiment 2 of this invention. It is a flowchart which shows operation | movement when the some key candidate is extracted in the receiver by Embodiment 2 of this invention. It is explanatory drawing which shows an example of the key candidate extraction of the receiver by Embodiment 3 of this invention. It is a block diagram of the receiver by Embodiment 3 of this invention. It is a flowchart which shows operation | movement of the receiver by Embodiment 3 of this invention. It is a block diagram of the receiver by Embodiment 4 of this invention. It is a block diagram of the receiver by Embodiment 5 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Receiving part, 11 Encryption / decryption part, 12 Key control part, 13, 13a, 13b, 13c, 13d Key candidate control part, 14 Determination part, 15 Media decryption part, 16 Output control part.

Claims (7)

A receiving unit for receiving the encrypted media data and a key information packet including a key for decrypting the encrypted media data;
If the key information packet received by the receiving unit is an error, a key candidate control unit that extracts a key candidate from the key information packet;
An encryption / decryption unit that decrypts the encrypted media data using the key candidates extracted by the key candidate control unit;
A determination unit that determines whether the media data decrypted by the encryption / decryption unit is correctly decrypted,
The key candidate control unit is a receiving device that determines a key candidate determined to be correctly decrypted by the determination unit as a correct key extracted from the key information packet.   The receiving apparatus according to claim 1, wherein the key candidate control unit detects a fixed pattern around the key candidate and extracts the key candidate based on a relative position of the fixed pattern. A key control unit that extracts a key from the error-free key information packet received by the reception unit and sends the key to the encryption / decryption unit;
The key control unit notifies the key candidate control unit of a key storage position in an error-free key information packet received in the past, and the key candidate control unit detects an error key based on the key storage position. The receiving apparatus according to claim 1, wherein a key candidate is extracted from the information packet.   The key candidate control unit, when there are a plurality of key candidates, provides all the key candidates to the encryption / decryption unit unless the determination unit determines that the key candidates are correctly decrypted among the plurality of key candidates. The receiving device according to any one of claims 1 to 3.   If the key information packet for generating the key is encrypted with another key and the other key information packet for generating the other key is an error, the key candidate control unit Other key candidates are extracted from the key information packet, and the media data is decrypted using the key obtained as a result of decrypting the key information packet using the other key candidate, and the decryption is normally decrypted. 5. The receiving device according to claim 1, wherein the key and the other key are determined to be correct when the determination unit determines that the key is correct. A media decrypting unit that inputs media data decrypted by an encryption / decryption unit using a key candidate, decrypts the input media data, and determines whether the decryption result is an error,
6. The reception according to claim 1, wherein the key candidate control unit determines that the key candidate is correct when the decryption result in the media decryption unit is not an error. apparatus. A media decryption unit that inputs media data encrypted and decrypted with a key candidate that the key candidate control unit determines to be a correct key, and decrypts the media data;
An output control unit that determines whether or not to output the data decrypted by the media decryption unit to the outside according to an instruction from the key candidate control unit;
The key candidate control unit instructs the output control unit to permit output when a key candidate determined to be a correct key and a key extracted from an error-free key information packet thereafter match. The receiving device according to any one of claims 1 to 6.

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