MXPA06009521A - Method and circuit for encrypting a data stream - Google Patents

Abstract

Current legislation requires the possibility of encryption when storing television programmes received by broadcast. However, legacy playback apparatuses will not be able to play back such encrypted data in a regular way, but possibly ina wrong way. This may result in problems like damage of speakers. Therefore, the invention intends to hide any of such possibly damaging streams by intentionally providing such streams with a wrong identification during the encryption process. The invention provides among others a method and circuit for encryption and a method and circuit for decryption. The invention is especially suitable for DVD recorders, but may also be employed for other video and/or audio recorders. The invention may even be used for encrypting non-audiovisual data.

Description

METHOD AND CIRCUIT OF ENCRYPTION OF DATA FLOW Brief Description of the Invention The invention relates to a method of encrypting a data stream comprising at least one stream of audiovisual data. The invention further relates to an encryption circuit of a data stream comprising at least one stream of audiovisual data. The invention also relates to a method of deciphering audiovisual data. The invention also relates to a circuit for deciphering audiovisual data. Furthermore, the invention relates to a computer program product comprising instructions that can be read by a computer for the programming of a processing unit. The invention also relates to a data carrier carrying this computer program product. The invention also refers to a programmed computer. The invention further relates to a data carrier that carries encrypted data using the method according to the invention. Current legislation requires the possibility of R F. 173133 performing the encryption procedure when storing television programs received by broadcasting. Television programs, in particular, television programs that are transmitted in digital form, can be provided with copy control information as metadata. The options for copy control information are, among others: no copying (recording is not allowed), a single copy (one recording is allowed, copying is not allowed) and free copying (free distribution) of the content allowed within the personal environment of the consumer). And even when the information of free copying is transmitted with the television programs, it could be required to encrypt and also that a part of the television program be stored. This requirement is placed in an additional radio broadcast or transmission notice. This requires the implementation of hardware and / or encryption software in video recorders such as DVD recorders. However, the problem is that the installed base, for example, of DVD players, does not support encryption. This can be solved by purchasing new equipment, although this is expensive. And based on the legacy team, the legacy audiovisual material can still be reproduced. Also, not all programs recorded by video recorders with encryption functionality encode programs when they are recorded. In addition to this, new video recorders with encryption functionality will be able to play the encrypted content. Therefore, it is not always directly necessary to discard the legacy DVD players. However, since the content on a DVD could be mixed, that is, the encrypted content is stored next to the non-encrypted content, the user could try to play the encrypted content on a non-condescending DVD player. With respect to the reproduction of the video data, this will originate not very interesting blocks on the screen. With respect to the reproduction of the audio data, this will cause noise, clicks, etc., which can be quite strong. Strong or intense noise may damage the equipment (speakers) and / or the user's ears, especially when he or she wears headphones. An object of the invention is to prevent the reproduction of these possibly harmful streams in legacy reproduction devices. To achieve this objective, the invention provides in a first aspect, a method of encrypting a data stream comprising at least one stream of audiovisual data, the method comprising the steps of: dividing the flow of audiovisual data into data segments; provide the data segments with data ID and a segment ID, the data ID are different from the data ID which are predetermined to identify the type of data in the audiovisual data stream; and the partial encryption of the data segments leaving the ID segment unencrypted. When during the encryption of audiovisual data for storage on a DVD, for example, the data ID of the audio data is modified into ID data without condescension with the DVD standard, a legacy DVD-player will not recognize the audio as such and therefore, it will not play any audio. In this way, the playback equipment speaker will not be damaged. The European Patent Application with Application No. 03104402.7 proposes a navigation structure that protects the encrypted content of the legacy devices through special navigation commands. However, this method depends on the fact that the recorders do a perfect job and that the players will never find their way around the navigation protection. In practice, this can not always be guaranteed. For example, some players allow the direct reproduction of a file that includes audiovisual data. In a further embodiment of the method according to the invention, the data stream comprises multiple streams of different types of audiovisual data and data segments are encrypted at least one stream of audiovisual data. Normally, audiovisual data is provided in several ways, at least with audio and video data. In addition to this, also the data related to interactive applications can be provided. An example of this is Digital Video Broadcasting with Multimedia Home Platform functionality (interactive) The different types of data are provided in separate flows, .multiplexed or that will be multiplexed in a single data flow. Still in a further embodiment of the method according to the invention, the data segments of at least one audiovisual data stream are provided with ID segments comprising ID data that are different from the ID data, which are previously predetermined to identify the type of data in the audiovisual data stream. When the data stream comprises multiple streams of audiovisual data (or other data types) and is only desired, the prevention of the reproduction of one of these streams comprises the data stream, only the data packet data ID for this stream It would have to be changed. In this way, only the data of this particular flow will not be reproduced by a legacy device, while the data of the other flow will be reproduced.

In another embodiment of the method according to the invention, the data segments are provided with additional data ID in the segment-ID, the additional data ID's are predetermined to identify the type of data in the audiovisual data stream and the additional data ID in an additional step are replaced by the ID data which is different from the ID data which are predetermined to identify the type of data in the flow of data. audiovisual data. An advantage of this mode is that this standard can be used in the existing circuit assemblies that provide the data segments with the predetermined data IDs that identify the type of data.

Obviously, this is in the cost of an additional separate circuit that modifies the default data ID. The invention provides in a second aspect a circuit for encrypting a data stream comprising at least one stream of audiovisual data, the circuit comprising: a segmentation unit that divides the flow of audiovisual data into data segments; a unit that provides the data segment with data ID in a segment ID, the data ID is different from the data ID which is predetermined to identify the type of data in the audio data stream; and an encryption unit that partially encodes the data segments, leaving the ID segment unencrypted. The invention provides in a third aspect an apparatus for the storage of data, which comprises, a receiver that captures the data; the circuit according to claim 10; and a storage device that stores the encrypted data in a storage medium. The invention provides in a fourth aspect a method of deciphering encrypted audiovisual data using the method according to claim 1, the method comprising the steps of: deciphering the partially encrypted data segments; recognizing that the data carried by the ID segment are different from the ID data which are predetermined to identify the type of data in the audiovisual data stream and recognize the current type of data comprised by the data segments; and forming a flow of audiovisual data from the data segments. The invention provides in a fifth aspect a circuit for the deciphering of audiovisual data encrypted by the circuit as claimed in claim 10, the circuit comprises: a decryption unit that decodes the partially encrypted data segments; an identification unit that recognizes that the data carried by the ID segment is different from the ID data which is predetermined to identify the type of data in the audiovisual data stream and the recognition of the current type of data comprised by the data segments; and a flow unit that forms a flow of audiovisual data from the data segments. The invention provides in a sixth aspect, an apparatus that delivers and retrieves audiovisual data, the apparatus comprising: a storage device that retrieves data from a storage medium; the circuit according to claim 15; and a circuit that delivers the flow of audiovisual data encryption. The invention provides in a seventh aspect a computer program product comprising instructions that can be read by computer for the programming of a processing unit executing the method according to claim 1. The invention provides in an eighth aspect a carrier of data carried by the computer program product as claimed in claim 1. The invention provides in a ninth aspect a programmed computer activated to execute the method according to claim 1. The invention provides in a tenth aspect a product of computer program comprising a computer-readable instruction for programming a processing unit executing the method according to claim 13.

The invention provides in the eleventh aspect of a data carrier carrying the computer program product as claimed in claim 13. The invention provides in a twelfth aspect a programmed computer that is activated to execute the method according to claim 13 . ' The invention provides in a thirteenth aspect a data carrier carrying encrypted data using the method according to claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further clarified by means of the figures, wherein: Figure 1 shows a video recorder 100 as a mode, of the apparatus for storing data according to the invention; Figure 2 shows a flowchart representing a method embodiment for the encryption of a data stream according to the invention; Figure 3 shows a data packet produced by the method represented by the flow chart shown by means of Figure 2; Figure 4 shows a DVD player as a mode of the apparatus that retrieves and delivers the data according to the invention; and Figure 5 shows a flowchart representing a method embodiment for the recovery and provision of data according to the invention.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows a video recorder 100 as a mode of the apparatus according to the invention. The video recorder 100 comprises a receiver 101, a demultiplexer 102, a video processor 103 as a supply unit, a coding circuit 110 as a mode of the circuit according to the invention, the coding circuit 110 comprises a multiplexer 104. , an encryption unit 105 and a pack identification unit 106. The video recorder furthermore copes an EVD 107 recorder unit with a storage device. The operation of the video recorder 100 will be described by means of Figure 1 and the flow chart 200 as shown in Figure 2, which shows a recording process as a mode of the process according to the invention. The processes of the flowchart 200 are labeled or marked as indicated in Table 1. Table 1 Table 1 (Continued) The recording process starts by means of a user input in the process step 200. In an additional mode, the recording process starts by means of an automatically generated input of a programming unit designed to program the recordings by means of the video recorder 100. Next, a data stream comprising data to be recorded is admitted by the receiver 101 in the process step 202. The data stream can be picked up or admitted by means of receiving a signal 150 comprising data through a wireless connection, a wireline broadcast connection such as a cable, or a point-to-point (virtual) connection such as .Broadband Internet; various modalities of the reception process stage 202 and the receiver 101 are possible. Having received the signal 150, the data stream is extracted from the signal and is provided to the demultiplexer 102. The extracted data stream is in this mode a transport stream comprising streams of audio and video data for a program of TV. In the further course of this description, as well as the claims accompanying this patent application, both types of data will be referred to as audiovisual data, even where there is only audio data or video data. The demultiplexer 102 separates the various streams of audiovisual data comprised by the program stream normally in an elementary audio stream and an elementary video stream. A preferred format for these elementary streams is the MPEG-2 format. The program flow could also comprise a stream with data for interactive television applications and a flow with data for the improvement of elementary audio flow and / or elementary video flow. In Figure 2, the demultiplexing process step is comprised by the reception processing stage 202. The elementary audio stream and the elementary video stream are provided to the video processor 103 for the dery of the audiovisual data comprised by the elementary streams. For this description, the supply means that the MPEG-2 data (in the case of the present embodiment) is decompressed and transformed for reproduction through a loudspeaker 120 and a television coding apparatus (not shown). In addition to the supply, the video recorder 100 also has the ability to record the received data. For this, the data picked up by the receiver 101 and demultiplexed by the demultiplexer 102 (both in the processing step 204) are divided into data segments in the processing step 206. The data segments are also known as packets (data) . Subsequently, the ID data is added to the segments in. process step 208 to identify the type of data comprised by the segments. The ID data identifies the type of data comprised by the segment and is predefined to facilitate the reproduction of the data stored by a reproduction apparatus such as a DVD player (Digital Versatile Disk). For the DVD standard, the values of the flow IDs as in Table 2 have been added. The ID data is comprised by a data segment header (or data packet). Table 2 also includes information on the Sub-flow IDs. The sub-flows are comprised by a private flow constituted by the total data flow on a DVD. The sub-flows provide additional information, complementary to the basic audio and video data. Examples are AC-2, audio, DTS (Digital Theater System), SDDS (Digital Dynamic Sound from Sony), LPCM (Modulation of Linear Impulse Code) and others. Table 2 In a subsequent process step 210, the segments are arranged in data packets. The data packets comprise data segments of a flow type. This implies that a data packet could comprise data from multiple sub-flows, although this is not the case in the preferred embodiment, since this is not allowed by the DVD standard. Optionally, the data packets comprise a padding packet when sufficient data from a stream is not available to fill 2kB of the aggregated packet data size. The packets are provided with a header for their identification and in order to provide the synchronization information that harmonizes the audio and video data. In a subsequent process stage. 212, data packets with audiovisual data are placed in sequence in a data stream. As prescribed by the DVD standard. These writing units are expensive products, it is important in this way limiting the number used to one. The process steps numbered 206 through 212 form a sub-process 230 which is carried out by the multiplexer 104. As will be appreciated by a person skilled in the art, these process steps could also be carried out through separate components. Once the packets have been placed in a stream, they are encrypted by the encryption unit 105 in the process step 214. This encryption process is performed partially, so that a playback device is still able to read. at least some data segment and the identification information of the data packet of each packet. Preferably, the first 128 bytes of a data packet are not encrypted. After the processing step 214, the data packets are obtained as shown in Figure 3. Figure 3 shows a data packet 300, comprising a packet header 301, a data segment header 302 and a payload 320. The packet header 301 comprises the data identifying the data packet, the data segment header 302 comprises a segment ID 312 that identifies the type of data comprised by the payload 320 (as noted in the Table 2) . The mixed information is comprised of two bits in the mixing identification bits 314. In a subsequent processing step 216, the data segment ID of the data segments comprising the audio data is modified by the identification unit of the data. pack 106. In this way, audio packets are not recognized by a playback apparatus such as a legacy DVD player. This is done to avoid the possible reproduction in a device that is not capable of deciphering the packets. When a legacy DVD player, i.e., a DVD player that does not comprise a mode of the decryption circuit according to the invention, would recognize an encrypted packet comprising audio data, the legacy DVD player would attempt to reproduce the encrypted data. Aungue is not intended, it is still possible that the audio is reproduced. This is because not all audio data is encrypted; the. The first part of the data packets stored on a DVD are in the clear and could comprise data that the DVD player would use for synchronization. Normally, this will cause a batch of noise that could damage the audio equipment such as the speakers, when reproduced by the headphones, it would damage the ears of the user wearing the headphones. When no audio data is recognized because the proper stream_id is not found, no audio will be played and only the decrypted video will be played. This is not very interesting to observe, although it does not damage the legacy DVD player. The inventors propose "the modification of the values stréam_id and sub_stream_id as shown in Table 3. As will be appreciated by a person skilled in the art, modifications of this scheme are possible; Table 3 simply provides a modality. 'Table 3 For the private stream, also the stream_id can be modified instead of the sub_stream_id. In Table 4, only the stream_ids are modified, but not the sub_stram__ids. The video, audio and sub_picture streams are now hidden. An additional advantage of not including the sub_stram_ids is that it is not necessary to analyze the flow to find the location of the flow ID, since it is always stored in the 18th byte of the packet.

Table 4 Having modified the data ID of the audio stream of the data to be stored, the encrypted data packets are stored by the DVD recording disk unit 107 in a process step 218. After all the data has been stored, the process ends in a terminator 220 of the flow chart 200. It will be apparent to a person skilled in the art that the altered data ID can also be directly added by the multiplexer 104, instead of a separate unit. Also, the order of the encryption and alteration of the ID data can be exchanged in an additional mode. Figure 4 shows a DVD player 400 as a mode of the apparatus for the delivery and retrieval of audiovisual data according to the invention. The DVD player 400 comprises a DVD disk drive 401 as a storage device, a decryption unit 402, a demultiplexer 403 and a video processor 404. The decryption unit 402 and the demultiplexer 403 form a circuit 410 a circuit mode for the decryption of data according to the invention. The video processor 404 can be included as an MPEG decoder. The method of operation of the DVD player 400 will be clarified by means of a flow chart 500 in Figure 5 which represents a recovery and delivery process as a mode of the data recovery and delivery method according to the invention. Table 5 When reproduction of encrypted data that is stored on a DVD in the processing step 502 is required, the data is retrieved from the DVD by means of the DVD disc drive 401 in a subsequent process step 504. Next, the packets are decoded by the decryption unit 402 in a process step 506. The demultiplexer 403 is adapted to recognize the modified data ID. This means that it is able to recognize the data for the MPEG audio stream, even when the stream_id is different from what has been defined by. the standard DVD. The identification of suitable flows is performed in a process step 508. In a subsequent process step 510, the demultiplexer forms elementary streams from the packets, supplying it to a video processor 404 that delivers it to provide a signal that can be reproduced on a loudspeaker 420 or a television connection box or coder (not shown). Process step 508 and process step 510 form a sub-process 520 which in this mode is performed by the demultiplexer 403. Next, the elementary streams are delivered for suitable reproduction by means of a loudspeaker and / or screen in a process step 512 by means of the video processor 404. Subsequently, the data delivered is reproduced by a loudspeaker 420 and a screen (not shown) in a process step 514. The recovery and delivery process that is represented by the flow diagram 500 it ends in a terminator 516 when all the data that will be reproduced has already been reproduced. In a further embodiment of the invention, the stream_id of the original audio stream is modified and an empty audio stream is provided with the prescribed audio stream_id. This could be applied to audio data types, as well as video or both types of data. The provision of empty data flows does not mean that all data flows are empty. For example, the minimum bit rate of an AC-3 stream is 64 kbps. A reproduction device as a mode of the apparatus that delivers and retrieves audiovisual data in accordance with the invention will discard the flow or void flows. The playback device will also recognize the stream_ids and decrypt and reproduce the decrypted data. Various other embodiments of the invention are possible without departing from the scope thereof. For example, a function that is described that is carried out by an element could also be performed by multiple elements and vice versa. Also, the data could be stored in a total range of data carriers ranging from optical carriers according to various standards such as Compact Disc®, Super Audio Compact Disc®, BlueRay® to solid-state carriers such as instant EEPROM circuits and even those that comprise digital video tape. As a person skilled in the art will understand, the invention could also be included as a computer program product comprising instructions capable of being read by a computer for programming a processing unit executing the methods according to the invention, a data carrier carrying this computer program product and a programmed computer that is activated to execute one or more of the methods according to the invention. In summary, the invention relates to the following: Current legislation requires the possibility of encryption when storing television programs received by broadcasting. However, legacy playback devices will not be able to reproduce this encrypted data on a regular basis, but may do so in the wrong way. This could cause problems such as damage to the speakers. Therefore, the invention aims to hide any of these possible harmful flows by intentionally providing these flows with a wrong identification during the encryption process. The invention provides among others a method and circuit for encryption and a method and circuit for deciphering. The invention is especially suitable for DVD recorders, although it could also be used for other video and / or audio recorders. The invention could even be used for the encryption of non-audiovisual data. It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (26)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. An encryption method of a data stream includes at least one stream of audiovisual data, characterized in that it comprises the steps of: (a) dividing the flow of audiovisual data in data segments; (b) providing the data segments with data ID in a segment ID, the data ID is different from the data ID which is predetermined to identify the type of data in the audio data stream; and (c) partially encrypt the data segments, leaving the ID segment unencrypted. The method according to claim 1, further characterized in that it comprises the step of creating data packets, each data packet includes at least one data segment and wherein at the stage of partially encrypting the data segments, the data ID segment at least in a data segment is unencrypted. The method according to claim 1, characterized in that the data stream comprises multiple streams of different types of audiovisual data and the data segments of at least one stream of audiovisual data are encrypted. The method according to claim 3, characterized in that the data segments of at least one audiovisual data stream are provided with ID segments comprising ID data that are different from the ID data that are predetermined to identify the data type in the flow of audiovisual data. The method according to claim 3, wherein the multiple streams of audiovisual data are provided simultaneously, further characterized in that it comprises the step of multiplexing the segments that include data from multiple streams of audiovisual data into an additional stream of data . The method according to claim 1, characterized in that the data segments are provided with additional data ID in the segment ID, the additional data ID are predetermined to identify the type of data in the audiovisual data stream and the additional data IDs are replaced in an additional step by the ID data which are different from the ID data which are predetermined to identify the type of data in the audiovisual data stream. The method according to claim 2, characterized in that the data packets are MPEG-2 data stream packets. 8. The method according to claim 1, characterized in that the ID data that are predetermined to identify the type of data in the audiovisual data stream are predetermined by the DVD standard. The method according to claim 1, further characterized in that it comprises the step of providing an empty audio-visual data stream of the same type as the audio-visual data stream for which non-predetermined ID data has been provided, the empty data stream audiovisuals is provided with predetermined ID data for the identification of this type of data. The method of storing a data stream that includes at least one stream of audiovisual data, characterized in that it comprises the step of receiving the data flow, the method according to claim 1 and the step of saving the segmented data and encrypted in a storage medium. 11. A circuit for encrypting a data stream includes at least one stream of audiovisual data, characterized in that it comprises: (a) a segmentation unit that divides the flow of audiovisual data into data segments; (b) a unit that provides the data segment with data ID in a segment ID, the data ID is different from the data ID which is predetermined to identify the type of data in the audio data stream; and (c) an encryption unit that partially encodes the data segments, leaving the ID segment unencrypted. The circuit according to claim 11, further characterized in that it comprises a packet formation unit that creates data packets, each data packet includes at least one data segment; and wherein in the step of partially encrypting the data segments, the segment ID of at least one data segment is unencrypted. 13. An apparatus for storing data, characterized in that it comprises: (a) a receiver that accepts data; (b) the circuit according to claim 11; and (c) a storage device that stores the encrypted data in a storage medium. 14. The method of deciphering encrypted audiovisual data using the method according to claim 1, characterized in that it comprises the steps of: (a) deciphering the partially encrypted data segments; (b) recognizing that the data carried by the ID segment is different from the ID data which are predetermined to identify the type of data in the audiovisual data stream and recognize the current type of data comprised by the data segments; and (c) forming a flow of audiovisual data from the data segments. 15. The method of recovering and delivering stored data using the method according to claim 10, characterized in that it comprises: (a) the step of recovering the data stored in it. storage medium; (b) the method according to claim 14; and (c) the stage of delivery of the deciphered stream of audiovisual data. 16. The circuit for deciphering audiovisual data encrypted by the circuit according to claim 11, characterized in that it comprises: (a) a decryption unit that decodes the partially encrypted data segments; (b) an identification unit that recognizes that the data carried by the ID segment is different from the ID data which is predetermined to identify the type of data in the audiovisual data stream and recognizes the current type of data comprised by the data segments. data; and (c) a flow formation unit that creates a flow of audiovisual data from the data segments. 17. - An apparatus that delivers and retrieves audiovisual data, characterized in that it comprises: (a) a storage device that retrieves data from a storage medium; (b) the circuit according to claim 16; and (c) a circuit that delivers the deciphered stream of audiovisual data. 18. The computer program product, characterized in that it comprises instructions that can be read by computer for the programming of a processing unit that executes the method according to claim 1. 19. The data carrier, characterized in that it carries the product of computer program according to claim 1. 20. The programmed computer, characterized in that it is activated to execute the method according to claim 1. 21. The computer program product, characterized in that it comprises instructions that can be read by computer for programming a processing unit executing the method according to claim 14. 22. The data carrier, characterized in that it carries the computer program product according to claim 14. 23. The computer programmed, characterized because it is activated to execute the conf method Ormity with claim 14. 24. The data carrier carrying the encrypted data, characterized in that it uses the method according to claim 1. 25. The data carrier according to claim 24, characterized in that it is a susceptible DVD disc. to be recorded again. 26. The data carrier according to claim 24, characterized in that it is a DVD disc capable of being rewritten.