JP2007311940A - Encryption device and decryption device - Google Patents

Abstract

In a stream encryption method, it is intended to enhance resistance to transmission data loss due to a transmission error or the like.
An initial value used for initializing a stream encryption algorithm is generated from data of a first encrypted packet, the stream encryption algorithm is initialized using the generated initial value, and stream encryption is performed. An encryption unit 103 that generates a second encrypted packet that stores the stream cipher data and a transmission unit 104 that transmits the encrypted packet are provided.
[Selection] Figure 1

Description

  The present invention relates to an encryption device and a decryption device of a stream encryption method.

In recent years, digital broadcasting for portable terminals has been put into practical use. As an encryption method for program data at the time of digital broadcasting for mobile terminals, a stream encryption method with a lighter processing load than a block encryption method generally used in content distribution such as the Internet, considering the processing capability of the mobile terminal Is considered preferable. In the stream encryption method, the state of the stream encryption algorithm of both the encryption device and the decryption device is indispensable for normal decryption.
Japanese Patent No. 3030341 Japanese Patent No. 3455748

  However, if a loss of transport packets storing stream cipher data occurs due to broadcast data transmission errors, etc. in digital broadcasting, the state of the stream cipher algorithms of both the encryption device and the decryption device will not match, resulting in a decryption error. Resulting in.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an encryption device and a decryption device of a stream encryption method that can enhance resistance to transmission data loss due to a transmission error or the like. There is.

  In order to solve the above-described problem, an encryption apparatus according to the present invention includes an initial value generation unit that generates an initial value used for initializing a stream encryption algorithm from data of a first encrypted packet, and the generation An encryption means for initializing a stream encryption algorithm using the generated initial value and performing stream encryption, an encryption packet generation means for generating a second encryption packet for storing the stream encryption data, and the encryption And a transmission means for transmitting the packet.

  The encryption apparatus according to the present invention includes an initial value generation means for generating an initial value used for initializing a stream encryption algorithm from the non-encryption target data of a packet having the encryption target data and the non-encryption target data. And an encryption means for initializing a stream encryption algorithm using the generated initial value and performing the stream encryption of the packet, and a transmission means for transmitting the encrypted packet.

  The encryption apparatus according to the present invention is characterized in that a plurality of the encryption means are provided, and the initialization packet generation means generates an initial value for each encryption means.

  The decryption apparatus according to the present invention includes: a receiving unit that receives an encrypted packet; an initial value generating unit that generates an initial value used for initializing a stream encryption algorithm from data of the first encrypted packet; And a decrypting means for initializing a stream cipher algorithm using the generated initial value and decrypting the stream cipher data stored in the second cipher packet.

  The decryption apparatus according to the present invention, receiving means for receiving an encrypted packet, initial value generating means for generating an initial value used for initialization of a stream encryption algorithm from unencrypted data of the encrypted packet, And a decrypting unit configured to initialize a stream cipher algorithm using the generated initial value and decrypt the stream cipher data stored in the cipher packet.

  The decoding apparatus according to the present invention is characterized in that a plurality of the decoding means are provided, and the initialization packet generating means generates each initial value for each decoding means.

  According to the present invention, it is possible to enhance resistance to transmission data loss due to a transmission error or the like in a stream encryption method.

  Hereinafter, embodiments of the present invention will be sequentially described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of a stream encryption method encryption apparatus 100 according to the first embodiment of the present invention.
In FIG. 1, a header conversion unit 101 performs header conversion of a transport packet (TS packet). The TS packet conforms to ISO / IEC 13818-1 (MPEG-2 system standard). The header conversion unit 101 rewrites the value of the transport_scrambling_control field in the header of the TS packet. The values “01”, “10”, and “11” in the transport_scrambling_control field indicate that encryption is performed. A value “00” in the transport_scrambling_control field indicates that encryption is not performed.

  The key ID insertion unit 102 stores the key ID in the TS packet. There are two types of key IDs, “Current” and “Next”. The key ID “Current” is an identifier of a key currently in use. The key ID “Next” is an identifier of a key to be used next.

  FIG. 2 shows a configuration example of a TS packet according to the present embodiment. In this embodiment, the header of the TS packet is extended, and fields for storing the key IDs “Current” (id_current) and “Next” (id_next) are provided.

  The encryption unit 103 performs stream encryption on the TS packet sequence. This encryption target is TS packets whose transport_scrambling_control field values are “01”, “10”, and “11”. Note that the header of the TS packet is not encrypted. The encryption unit 103 initializes the stream encryption algorithm for each TS packet to be encrypted.

  The encryption unit 103 outputs a TS packet sequence including the encrypted TS packet to the transmission unit 104. The transmission unit 104 transmits the TS packet sequence received from the encryption unit 103.

FIG. 3 is a block diagram showing the configuration of the encryption unit 103 according to the first embodiment of the present invention.
In FIG. 3, the stream encryption algorithm calculation unit 111 reads the encryption target data (data in the data_byte field shown in FIG. 2) from the encryption target TS packet, and performs the stream encryption process. In the stream encryption process, the stream encryption algorithm calculation unit 111 first initializes the stream encryption algorithm using the initial value generated by the initial value generation unit 113. Next, after the initialization is completed, the data to be encrypted is stream encrypted. In initialization of the stream encryption algorithm, the key IDs “Current” (id_current) and “Next” (id_next) are read from the TS packet to be encrypted, and a key used for stream encryption is prepared.

  The encrypted packet generator 112 stores the stream cipher data in the data_byte field of the TS packet to be encrypted and outputs it.

  The initial value generation unit 113 generates an initial value used for initializing the stream encryption algorithm from the data of the encrypted TS packet (hereinafter referred to as “encrypted TS packet”). This generated initial value is used to initialize the stream encryption algorithm in the stream encryption process for the next encryption target TS packet. That is, initialization of the stream encryption algorithm for generating the next second encrypted TS packet is performed using the initial value generated from the data of the first encrypted TS packet.

  Data used for initial value generation is data at a predetermined position in the encrypted TS packet. For example, the last data of the encrypted TS packet may be used.

  Further, the encryption unit 103 can have a plurality of stream encryption processes. In each stream encryption process, stream encryption is performed on the corresponding TS packet to be encrypted. In each stream encryption process, the stream encryption algorithm is initialized independently. In each stream encryption process, the TS packet to be encrypted is determined based on the PID field value.

Next, the decryption apparatus of the stream encryption method according to the first embodiment will be described.
FIG. 4 is a block diagram showing a configuration of the stream encryption type decryption apparatus 200 according to the first embodiment of the present invention.
In FIG. 4, the reception unit 201 receives a TS packet sent from the encryption device 100. The receiving unit 201 performs error detection and error correction processing on the received TS packet.

  The packet distribution unit 202 distributes the TS packet output from the reception unit 201 to each destination according to the PID field value in the header. Here, the encrypted TS packet (transport_scrambling_control field values “01”, “10”, and “11”) is output to the decryption unit 203 corresponding to the PID field value. Further, other TS packets that are not encrypted are output from the decryption apparatus 200 as they are.

  The decryption unit 203 receives the encrypted TS packet from the packet sorting unit 202 and decrypts the stream cipher. The decryption unit 203 initializes the stream encryption algorithm for each encrypted TS packet.

FIG. 5 is a block diagram showing a configuration of the decoding unit 203 according to the first embodiment of the present invention.
In FIG. 5, the stream cipher algorithm calculation unit 211 reads stream cipher data from the data_byte field of the encrypted TS packet and performs a stream cipher decryption process. In the decryption processing of the stream cipher, the stream cipher algorithm calculation unit 211 first initializes the stream cipher algorithm using the initial value stored in the initial value storage unit 212. Next, after the initialization is completed, the stream cipher data is decrypted. In the initialization of the stream encryption algorithm, the key IDs “Current” (id_current) and “Next” (id_next) are read from the encrypted TS packet, and a key used for decoding the stream cipher is prepared.

  The initial value generation unit 213 generates an initial value used for initializing the stream encryption algorithm from the data of the encrypted TS packet. The initial value generation unit 213 stores the generated initial value in the initial value storage unit 212. This stored initial value is used to initialize the stream cipher algorithm in the stream cipher decryption process for the next encrypted TS packet. That is, the initialization of the stream encryption algorithm for decrypting the next second encrypted TS packet is performed using the initial value generated from the data of the first encrypted TS packet.

  Data used for initial value generation is data at a predetermined position in the encrypted TS packet. The predetermined position is defined in advance with the encryption apparatus 100.

  The decoding unit 203 outputs the decoded TS packet to the playback device 300.

  In the reproduction apparatus 300, the decoded TS packet is reproduced. In the example of FIG. 4, the playback device 300 includes an image playback unit 301, an audio playback unit 302, and a data broadcast display unit 303. The decoding device 200 is provided with a decoding unit 203 corresponding to each of the image reproduction unit 301, the audio reproduction unit 302, and the data broadcast display unit 303. In the image reproducing unit 301, the audio reproducing unit 302, and the data broadcast display unit 303, the TS packets output from the corresponding decoding units 203 are reproduced. The configuration of the playback apparatus 300 shown in FIG. 3 is an example, and the media type (sound, image, data, etc.) can be changed as appropriate.

  According to the first embodiment described above, the encryption method and the decryption device use the initial value generated from the data of the first encrypted TS packet and use the stream encryption algorithm related to the next second encrypted TS packet. Is initialized, and the state of the stream encryption algorithm in the encryption process matches the state of the stream encryption algorithm in the decryption process. Therefore, even if the encrypted TS packet is lost due to a transmission error or the like and the state of the stream encryption algorithm in both the encryption process and the decryption process is temporarily inconsistent, the encryption is performed when the next encrypted TS packet is received. The state of the stream encryption algorithm in both the process and the decryption process matches, and normal decryption can be resumed. As a result, in the stream encryption method, it is possible to enhance resistance to transmission data loss due to a transmission error or the like.

  In the above-described embodiment, key sharing is realized between the encryption device and the decryption device by notifying the decryption device of the key ID using the TS packet, but the key sharing method is limited to this. Instead, key sharing between the encryption device and the decryption device may be realized by other methods.

[Second Embodiment]
In the second embodiment, the encryption unit 103 is changed in the encryption device 100 shown in FIG. 1, and the decryption unit 203 is changed in the decryption device 200 shown in FIG. Other parts of the encryption device 100 and the decryption device 200 are the same as those in the first embodiment, and a description thereof will be omitted.

  FIG. 6 is a block diagram showing a configuration of the encryption unit 103 according to the second embodiment of the present invention. In FIG. 6, parts corresponding to those in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted.

  In FIG. 6, an initial value generation unit 121 generates an initial value used for initialization of a stream encryption algorithm from non-encryption target data of a TS packet to be encrypted. This generated initial value is used to initialize the stream encryption algorithm in the stream encryption process for the same TS packet. That is, when stream encrypting a TS packet to be encrypted, the initial value of the stream encryption algorithm for stream encrypting the TS packet using the initial value generated from the unencrypted data of the same TS packet Is done.

  The non-encryption target data used for initial value generation is non-encryption target data at a predetermined position in the TS packet to be encrypted. For example, the header data shown in FIG. 2 may be used.

  FIG. 7 is a block diagram showing a configuration of the decoding unit 203 according to the second embodiment of the present invention. In FIG. 7, the same reference numerals are given to portions corresponding to the respective portions in FIG.

  In FIG. 7, the initial value generation unit 221 generates an initial value used for initializing the stream encryption algorithm from the non-encryption target data of the encrypted TS packet. The initial value generation unit 221 outputs the generated initial value to the stream cipher algorithm calculation unit 211. The initial value generated by the initial value generating unit 221 is used for initializing the stream cipher algorithm in the stream cipher decryption process for the same encrypted TS packet. That is, when the encrypted TS packet is decrypted, the initialization of the stream cipher algorithm for decrypting the encrypted TS packet is performed using the initial value generated from the non-encrypted data of the same encrypted TS packet. Done.

  The non-encryption target data used for initial value generation is non-encryption target data at a predetermined position in the TS packet to be encrypted. The predetermined position is defined in advance with the encryption apparatus 100.

  According to the second embodiment described above, the stream encryption algorithm is initialized in units of packets in the encryption device and the decryption device, the state of the stream encryption algorithm in the encryption process, the state of the stream encryption algorithm in the decryption process, Match and normal decoding is performed. As a result, in the stream encryption method, it is possible to enhance resistance to transmission data loss due to a transmission error or the like.

  FIG. 8 shows an embodiment of a digital broadcasting system for mobile terminals to which the encryption device and the decryption device according to the present invention are applied. In FIG. 8, a broadcast station 400 encrypts content to be broadcast by a stream encryption method, and transmits the stream encryption on a digital broadcast wave. Examples of the media type of content include voice, image, data, and the like. The portable terminal 500 receives the stream cipher that is on the digital broadcast wave, and reproduces it while decrypting the stream cipher with the decryption key. The user views the content reproduced on the mobile terminal 500.

FIG. 9 is a block diagram showing the configuration of the digital broadcast system for mobile terminals shown in FIG.
In FIG. 9, the user obtains a decryption key corresponding to the content to be viewed from the pseudo license purchase server 600 in advance. In the portable terminal 500, the key acquisition module 501 accesses the pseudo license purchase server 600 via the Internet and downloads the decryption key. The decryption key is supplied to the content decryption module 502. The decryption key may be paid or free.

  In the broadcasting station 400, the TS stream generation tool 401 generates a TS packet sequence (TS stream) composed of TS packets in which content is stored. The TS stream is subjected to stream encryption by the TS stream encryption tool 402. At this time, the TS stream encryption tool 402 initializes the stream encryption algorithm every time the TS packet is encrypted. This initialization method may be the method of the first embodiment described above or the method of the second embodiment. The encrypted TS stream (encrypted TS stream) is transmitted on the digital broadcast wave by the broadcast wave transmitting device group 403.

  In the portable terminal 500, the digital TV application 504 receives the encrypted TS stream on the digital broadcast wave. The content decryption module 502 decrypts the stream cipher for the received encrypted TS stream. The content included in the decrypted TS stream is reproduced for each media type by each media decoder 503.

Next, the processing procedure of the content decryption module 502 shown in FIG. 9 will be described.
As shown in FIG. 9, the decoding module processing procedure includes an initialization step S1 and a decoding step S2.

  First, in the initialization step S1, the decoding module 510 is initialized by an initialization method corresponding to the broadcast station 400. The decryption module 510 has a stream encryption algorithm. In the initialization, the decryption key received from the key acquisition module 501 is set. The initialization step S1 is executed every time the encrypted TS packet is decrypted.

  Next, in the decryption step S2, the ciphertext of the stream cipher system is decrypted by the initialized decryption module 510, and the plaintext of the decryption result is output in stream format. The ciphertext of the stream encryption method is acquired from the received encrypted TS packet. When the decryption of one encrypted TS packet is completed, the process returns to the initialization step S1.

  According to the present embodiment, the TS packet for storing the stream cipher data is lost due to a transmission error of the broadcast data in digital broadcasting, and the state of the stream cipher algorithm on both the broadcasting station side and the portable terminal side becomes inconsistent. Even if the reception status of the digital broadcast becomes unstable, the status of the stream encryption algorithm on both the broadcasting station side and the portable terminal side should be immediately matched to restore the digital broadcast reception status to a good state. Can do. Thereby, it becomes possible to contribute to the quality improvement of the digital broadcasting for portable terminals.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.
For example, in the above-described embodiment, an example in which the present invention is applied to a digital broadcasting system for mobile terminals has been described. However, the present invention can be applied to various broadcasting systems and communication systems.

1 is a block diagram showing the configuration of a stream encryption method encryption apparatus 100 according to a first embodiment of the present invention. FIG. It is a figure which shows the structural example of the transport packet (TS packet) which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structure of the encryption part 103 which concerns on 1st Embodiment of this invention. 1 is a block diagram showing a configuration of a stream encryption type decryption apparatus 200 according to a first embodiment of the present invention. FIG. It is a block diagram which shows the structure of the decoding part 203 which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structure of the encryption part 103 which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the decoding part 203 which concerns on 2nd Embodiment of this invention. It is explanatory drawing which shows one Example of the digital broadcasting system for portable terminals to which the encryption apparatus and decryption apparatus which concern on this invention are applied. It is a block diagram which shows the structure of the digital broadcasting system for portable terminals shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Encryption apparatus, 101 ... Header conversion part, 102 ... Key ID insertion part, 103 ... Encryption part, 104 ... Transmission part, 200 ... Decryption apparatus, 201 ... Reception part, 202 ... Packet distribution part, 203 ... Decryption part , 111, 211... Stream encryption algorithm calculation unit, 112, encrypted packet generation unit, 113, 121, 213, 221, initial value generation unit, 212, initial value storage unit, 400 ... broadcasting station, 401 ... TS stream generation tool , 402 TS broadcast encryption tool, 403 Broadcast wave transmitting device group, 500 Mobile terminal, 501 Key acquisition module, 502 Content decryption module, 503 Media decoder, 504 Digital TV application, 510 Decryption module

Claims (6)

Initial value generating means for generating an initial value used for initializing the stream encryption algorithm from the data of the first encrypted packet;
An encryption means for initializing a stream encryption algorithm using the generated initial value and performing stream encryption;
Encrypted packet generating means for generating a second encrypted packet for storing the stream cipher data;
Transmitting means for transmitting the encrypted packet;
An encryption device comprising: Initial value generation means for generating an initial value used for initialization of a stream encryption algorithm from the non-encryption target data of a packet having the encryption target data and the non-encryption target data;
An encryption unit that initializes a stream encryption algorithm using the generated initial value and performs stream encryption of the packet;
Transmitting means for transmitting the encrypted packet;
An encryption device comprising: A plurality of the encryption means are provided,
3. The encryption apparatus according to claim 1, wherein the initialization packet generation unit generates an initial value for each encryption unit. Receiving means for receiving the encrypted packet;
Initial value generation means for generating an initial value used for initialization of a stream encryption algorithm from data of the first encrypted packet;
Decryption means for initializing a stream cipher algorithm using the generated initial value and decrypting the stream cipher data stored in the second encrypted packet;
A decoding device comprising: Receiving means for receiving the encrypted packet;
Initial value generating means for generating an initial value used for initializing a stream cipher algorithm from unencrypted data of the encrypted packet;
Decryption means for initializing a stream cipher algorithm using the generated initial value and decrypting the stream cipher data stored in the encrypted packet;
A decoding device comprising: A plurality of the decoding means are provided,
6. The decoding apparatus according to claim 4, wherein the initialization packet generating unit generates an initial value for each decoding unit.

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