JP2009027436A - Apparatus for partial encryption and decryption, its method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To preferentially select and encrypt data having a high use value in partial encryption. <P>SOLUTION: In a partial encryption apparatus 100, an encryption condition determiner 130 determines whether the next data is to be encrypted in response to a fluctuation of a value of preceding data, with respect to map data stored in a data memory 110 which is a target for encryption, and an encryption part 160 performs partial encryption based on the results. The encrypted data is similarly decrypted by a partial decryption apparatus 200. It is determined that a portion with a large fluctuation of target data is data having a high use value, and this data is encrypted preferentially. Further, it is determined whether encryption is required from the preceding data, whereby it is possible to prevent size increase in an encrypted text obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for partially encrypting and decrypting data.

  A car navigation system (hereinafter referred to as a car navigation system) processes map data and provides traffic guidance information to a user. Conventionally, a DVD (Digital Versatile Disc) has been used as the map data recording means, but recently, a product using a recording device inside the car navigation system such as a HDD (Hard Disk Drive) having a larger capacity and higher speed than the DVD. Is becoming mainstream.

  In an HDD type car navigation system, when map data becomes old due to construction or removal of roads or buildings, it is necessary to update the data in the car navigation system to the latest in order to provide appropriate traffic information to the user. In the case of a conventional DVD type car navigation system, a DVD on which map data is recorded can be sold to a user, and the user can easily update it by replacing it with an old disk. On the other hand, in the case of the HDD type car navigation system, it is difficult for the user to replace the HDD itself, and therefore usually map data must be copied to the HDD by some means. As a means for performing this copying, a method is generally used in which a DVD on which map data is recorded is inserted into a car navigation system and copied to the HDD.

  At this time, there is a concern that if the map data is recorded on the DVD as it is, illegal use such as illegal copying of data or analysis of technical know-how is performed. Therefore, it is desired to prevent such unauthorized use by encrypting data, recording it on a DVD, and decrypting it when writing it to the HDD. Against this background, the following techniques have been proposed.

  First, as general encryption techniques, various general-purpose encryption algorithms such as DES (Data Encryption Standard) and AES (Advanced Encryption Standard) have been developed and widely used. However, in general, cryptographic computation consumes a lot of execution time of a CPU (Central Processing Unit) that is a processing unit of a computer device. Therefore, when enciphering and decrypting all large data such as map data A lot of processing time is required. In view of this, there has been proposed means for shortening the processing time by performing partial encryption (hereinafter referred to as partial encryption) instead of performing the same encryption process on all data.

  For example, the technique disclosed in Patent Document 1 discloses an apparatus and a program for determining a place to be encrypted using a result output from a calculation result of a predetermined function. By partially encrypting the data with this main technology, even if the entire data is not encrypted, it becomes practically difficult to view the content particularly in the case of music data, video data, etc. It becomes possible to prevent.

  As another method for shortening the decoding time, the technique described in Patent Document 2 can be used. In the technique described in Patent Document 2, when data is encrypted, each part of data having different required security levels is encrypted with a separate encryption key for each part. For example, if the data consists of several files, and the utility value of the recorded data varies from file to file, instead of simply encrypting all the files, only the high-value files are encrypted. Processing is possible.

  By using the various partial encryption techniques described above, it is possible to reduce the time required for encryption and decryption of map data, and it is possible to reduce the time required for updating.

JP 2006-270343 A JP 2006-80658 A

  However, the techniques described in Patent Documents 1 and 2 have the following problems.

  First, in the technique described in Patent Document 1, the location where encryption is performed and the location where encryption is actually required do not always match. For example, map data for car navigation is generally recorded as binary data in accordance with a specific data format in order to enable high-speed data processing. In other words, in addition to the valid values for road / building coordinate data and various search data, the format stipulates that mere 0 (zero) or a specific numerical value that means no value is entered continuously. There are many places to appear. When the technique described in Patent Document 1 is simply applied to such data, encryption is performed only in a non-sense area where zero or a specific numerical value is continuous, and no encryption is applied to data having a high utility value. May not be applied.

  Next, the technique described in Patent Document 2 performs encryption according to the security level for each data portion. For this purpose, the data to be encrypted is stored in a security level n, It is assumed that they are clearly separated. On the other hand, in map data for car navigation, coordinate data of roads and buildings with high utility value, various facility data for search, and other information are mixed in one file according to a specific format. Therefore, when the technique described in Patent Document 2 is used, for example, the header address such as security level n must be added to the ciphertext for the data at the offset address m in the file, and the data size of the ciphertext is It will become huge.

  In view of the above points, the present invention provides a case where data having high utility value is preferentially encrypted and data having different utility values are mixed in a file when the data is partially encrypted. It is another object of the present invention to provide an encryption / decryption device, a method thereof, and a program for performing partial encryption without increasing the size of the ciphertext.

  In order to solve the above-described problems, the present invention performs partial encryption on data to be encrypted, such as map data, for determining whether or not the next data needs to be encrypted according to the characteristics of the immediately preceding data. It is characterized by that. Normally, coordinate data and search data, which are highly useful data, can take various values, and therefore, in the portion where these data are described, the value varies greatly. On the other hand, data with low utility value, for example, data in which the same numerical value such as 0 (zero) continues is hardly changed.

  The present invention uses such characteristics of map data, etc., and estimates that the portion where the value fluctuates heavily is data having high utility value, and encrypts only the portion where the value fluctuates significantly, This realizes preferential encryption of data with high utility value. In addition, the present invention determines whether or not encryption is necessary from immediately preceding data, thereby reducing the addition of header information and preventing an increase in ciphertext size.

  In order to perform such partial encryption, the present invention is a partial encryption device that partially encrypts data, and includes a data input unit that reads data, and encryption of subsequent data with reference to the read data. There is provided a partial encryption apparatus comprising an encryption condition determination unit for determining necessity, an encryption unit for encrypting data, and a data output unit for outputting encrypted data.

  Further, in order to decrypt the data encrypted by the partial encryption device, the present invention is a partial decryption device for decrypting the partially encrypted data, a data input unit for reading the encrypted data, A decoding unit that decodes the read data; a decoding condition determination unit that determines whether the subsequent data needs to be decoded by referring to the decoded data; and a data output unit that outputs the decoded data. A partial decoding apparatus characterized by the above is provided.

  According to the present invention, it is possible to partially encrypt only data with high utility value included in map data, and the time required for decryption can be shortened.

  Hereinafter, the best mode of the present invention will be described in detail with reference to the drawings.

  Hereinafter, the DVD-based map update system according to the first embodiment will be described with reference to FIGS. 1 to 4. In the first embodiment, a description will be given of a system in which map data for HDD update is encrypted and recorded on a DVD, and the DVD on which the encrypted data is recorded is inserted into a car navigation disk drive to rewrite the car navigation HDD. To do. In this embodiment, when the map data is partially encrypted, whether or not the 1-byte input data needs to be encrypted is determined with reference to the immediately preceding 2 bytes. At the time of decoding, the necessity of decoding one byte of input data is determined by referring to the two bytes immediately before decoding.

  FIG. 1 shows an overall configuration diagram of a DVD-based map update system. This system includes a partial encryption device 100, a partial decryption device 200, and an update DVD 300. The partial encryption device 100 corresponds to a device that encrypts the map data and records it on a DVD, and the partial decryption device 200 corresponds to the car navigation system.

  As shown in FIG. 1, the partial encryption device 100 has a data recording unit 110 that records map data to be encrypted, and a data input that reads map data from the data recording unit 110. Unit 120, encryption condition determination unit 130 that determines whether or not the next data needs to be encrypted with reference to the read data, encryption condition recording unit 140 that records the encryption condition, and encryption based on the output of encryption condition determination unit 130 Encryption selector 150 for switching necessity of encryption, encryption unit 160 for encrypting data, key recording unit 170 for recording key information used for encryption, and encrypted map data (generically referred to as encrypted data for convenience) The data output unit 180 outputs the data.

  It goes without saying that such a function can be realized by a normal computer device such as a personal computer (PC). As is well known, an ordinary computer device includes a CPU as a processing unit, a read only memory (ROM), a random access memory (RAM), a large capacity HDD, and a DVD recording device, for example. The data output unit is connected by a bus or the like. The functional blocks of the encryption condition determination unit 130, the encryption selection unit 150, and the encryption unit 160 described above are usually configured by programs executed by the CPU. These programs are stored in a ROM or the like. The data recording unit 110, the encryption condition recording unit 140, and the key recording unit 170 correspond to the above-described storage unit.

  On the other hand, the partial decryption device 200, which is a car navigation system, refers to the data input unit 220 for inputting the encrypted map data and the decrypted map data as shown in FIG. An encryption condition determination unit 230 that determines whether or not the data is decrypted, an encryption condition recording unit 240 that records the encryption condition, an encryption selection unit 250 that switches the necessity of decryption based on the output of the encryption condition determination unit 230, and data A decryption unit 260 for decrypting data, a key recording unit 270 for recording key information used for decryption, a data output unit 280 for outputting decrypted map data, and a data recording unit for recording decrypted data 290. Also in the partial decoding apparatus 200, the functional blocks other than the data input unit 220, the data output unit 280, and the recording units 240, 270, and 290 are executed by the CPU constituting the processing unit in the partial decoding apparatus 200. Consists of programs.

  The update DVD 300 is a general DVD, and is created by recording the map data encrypted by the partial encryption device 100 by the data output unit 180. In this embodiment, the means for transmitting data between the partial encryption device 100 and the partial decryption device 200 is not limited to the DVD, but network communication technology represented by IP (Internet Protocol), USB (Universal), and the like. Serial bus) and other bus communication technologies may be used. In this case, the data output unit 180 and the data input unit 220 include a transmission / reception unit for a communication path and a USB interface unit.

  FIG. 2 shows a partial example of map data to be encrypted in the DVD-based map update system of the first embodiment. This map data is data stored in the data recording units 110 and 290. In FIG. 2, the diagram denoted by reference numeral 111 shows the data format of the map data, and the diagram denoted by reference numeral 112 shows an example of the actual value of the data. The example shown in FIG. 2 shows a state in which two XY coordinates that are data having high utility value and 0 (zero) that is data having low utility value are stored in the vicinity. As is apparent from FIG. 2, the X coordinate and the Y coordinate are each expressed as 2-byte data. In this embodiment, as shown in FIG. 2, when the X coordinate appears following flag information with almost no change in value (0x00, 0x00, 0x22, 0x32 in FIG. 2), the last 0x32 encryption is required. No is determined according to the difference between the immediately preceding 2 bytes 0x00 and 0x22 (the lower 1 byte of flag 3 and the upper 1 byte of the X coordinate). That is, by encrypting the lower 1 byte of the X coordinate, it becomes possible to hide the details of the X coordinate, which is highly useful data.

  The data recorded in the encryption condition recording units 140 and 240 of the partial encryption device 100 in FIG. 1 is a numerical value indicating a specific threshold value. The data recorded in the key recording units 170 and 270 is byte data indicating an encryption key. This key does not limit the encryption algorithm, and may be a key of a common key encryption technique or a key of a public key encryption technique. The above data may be fixed values set in advance or may be setting information set before encryption processing for the partial encryption device 100 and the partial decryption device 200.

  Hereinafter, the specific operation of the first embodiment will be described along the flow of partial encryption and decryption processing.

  In the partial encryption device 100, the data input unit 120 reads the map data recorded in the data recording unit 110 byte by byte and inputs the map data to the encryption condition determination unit 130 and the encryption selection unit 150.

  FIG. 3 is a flowchart showing the operation of the encryption condition determination unit 130 when 1 byte of data is input. The encryption condition determination unit 130 first calculates the absolute value (indicated by the variable d) of the difference between the input data 1 byte (indicated by the variable V) and the immediately preceding data 1 byte (indicated by the variable PrevV) (step d). S131). Note that the initial value of the variable PrevV is 0. Next, the threshold value which is the encryption condition is read from the encryption condition recording unit 240 and stored in the variable T (step S132). Next, it is determined whether or not the difference calculated in step S131 satisfies the encryption condition acquired in step S132 (step S133). If the encryption condition is satisfied (Yes), the information indicating “encryption is required” is output to the encryption selection unit 150 and the process ends (step S134). If the encryption condition is not satisfied (No), information indicating “encryption not required” is output to the encryption selection unit 150 (step S135). Finally, the value of the variable V is stored in the variable PrevV, and the process ends (step S136).

  FIG. 4 is a flowchart showing the operation of the cipher selection unit 150 that has received an output indicating whether encryption is necessary from the cipher condition determination unit 130. Note that a variable “Mode” used in the following description is a variable that stores whether encryption of the next data after the current data is necessary, and has an initial value of 0 (zero). In the cipher selection unit 150, first, when the variable Mode indicates “encryption required”, the data 1 byte passed from the data input unit 120 is output to the cipher unit 160. If the variable Mode indicates “encryption not required”, the input 1 byte of data is output to the data output unit 180 as it is (step S151). Next, the encryption condition determination unit 130 outputs whether the encryption is necessary or not in the variable Mode, and the process ends (step S152).

  By performing the above procedure for each byte input from the data input unit 120, the data is partially encrypted and stored in the update DVD 300 as encrypted data.

  Next, a procedure for decrypting the encrypted data in the partial decryption apparatus 200 will be described. The decryption procedure of the encrypted data is basically the same as the processing procedure in the partial encryption device 100.

  In the partial decryption device 200, first, the data input unit 220 reads the encrypted data described in the update DVD 300 byte by byte and outputs it to the decryption selection unit 250.

  The operation of the decryption selection unit 250 is the same as that of the encryption selection unit 150 in the partial encryption device 100 shown in FIG. That is, when the variable Mode indicates “decoding required”, the decoding selection unit 250 outputs 1 byte of data passed from the data input unit to the decoding unit 260. When the variable Mode indicates “decoding is not required”, 1 byte of data is output to the data output unit 280 as it is. Next, the output of the decoding condition determination unit 230 is stored in the variable Mode, and the process ends.

  Data decrypted by the decrypting unit 260 or passed to the data output unit 280 without being decrypted (sometimes referred to as decrypted data for convenience) is recorded in the data recording unit 290 and also includes a decryption condition determining unit. 230. By outputting the decrypted data to the decryption condition determining unit 230, as described above, the partial decryption apparatus 200 determines whether or not the 1-byte decryption of the input encrypted data is necessary. This is determined with reference to the decoded data. Note that the first 1-byte data of the input encrypted data is unencrypted data.

  The operation of the decryption condition determination unit 230 to which the data is passed is the same as the operation of the encryption condition determination unit 130 shown in FIG. That is, the decoding condition determination unit 230 first calculates the absolute value of the difference between the input 1 byte of data and the immediately preceding 1 byte of data. Next, the decoding condition is read from the decoding condition recording unit 240, and it is determined whether or not the decoding condition is satisfied. When the decryption condition is satisfied, information indicating “decryption is necessary” is output to the decryption selection unit 250, and when the encryption condition is not satisfied, information indicating “decryption is not necessary” is output to the process.

  Through the above processing, the encrypted map data recorded on the update DVD 300 is decrypted and written into the data recording unit 290 as decrypted data.

  Note that the decryption condition described above is predetermined threshold data as in the previous encryption condition, and is the same as the previous encryption condition or other threshold data selected in association with the threshold data of the previous encryption condition. There is a case. Therefore, it should be noted that the “decryption condition” may be called “encryption condition”. In this embodiment, the data to be encrypted or decrypted has been described as data in units of 1 byte. However, the present invention is not limited to this, and any data having a predetermined unit length may be used. Needless to say.

  According to the present embodiment described above, when the data on the HDD of the car navigation system is updated by the update DVD, only the portion where the data fluctuation is severe is selectively encrypted. It is possible to update the data on the HDD of the car navigation system by creating an update DVD that encrypts.

  Hereinafter, the maintenance terminal base map update system according to the second embodiment will be described with reference to FIGS. The second embodiment is a system for updating a map using a maintenance terminal, for example, a PC that exists in a dealer. In this system, the map data is first encrypted and recorded on a DVD, then the data on the DVD is installed in the dealer's maintenance terminal, and finally the maintenance terminal and the car navigation system are connected to transfer the data on the maintenance terminal. Update the map by installing it in the car navigation system. In this way, most of the data decryption processing is performed by a high-performance maintenance terminal, and the decryption processing performed on the car navigation side can be minimized. It becomes possible to encrypt the entire data.

  FIG. 5 shows an outline of the maintenance terminal base map update system of the second embodiment. FIG. 5 shows a partial encryption device 400, first and second partial decryption devices 500-1, 2 and two pieces of encrypted data 310 and 320 inputted to the two partial decryption devices 500-1, 2. Is shown. The partial encryption device 400 corresponds to a device that encrypts the map data and records it on a DVD, and the first partial decryption device 500-1 serves as a second partial decryption to a maintenance terminal installed in the dealer. The conversion apparatus 500-2 corresponds to a car navigation system.

  Most of the encrypted data 310 encrypted by the partial encryption device 400 is encrypted, is decrypted via the first partial decryption device 500-1, and only a specific portion is encrypted. The encrypted data 320 is output. The encrypted data 320, which is mostly decrypted, is input to the second partial decryption device 500-2 and completely decrypted.

  FIG. 6 is a configuration diagram of the partial encryption device 400 in the maintenance terminal base map update system according to the second embodiment. The partial encryption device 400 includes a data recording unit 410 that records map data to be encrypted, a multistage encryption condition recording unit 420 that records a plurality of encryption conditions for performing partial encryption, and a multistage encryption condition. The setting unit 430 for setting the multi-stage encryption according to the multi-stage encryption condition, a plurality of multi-stage connected partial encryption sections 450-1 and 450, and the data encrypted in the final stage and the multi-stage encryption condition are output. The multi-stage data output unit 440 is configured.

  Each of the partial encryption units 450-1 and 450-2 connected in multiple stages in the partial encryption device 400 has the same configuration as that of the partial encryption device in the first embodiment, and refers to the data input unit 120 for data and the read data. The encryption condition determining unit 130 for determining whether or not the next data needs to be encrypted, the encryption selecting unit 150 for switching the necessity of encryption based on the output of the encryption condition determining unit 130, the encryption unit 160 for encrypting the data, the encryption Including a key recording unit 170 that records key information used for. Note that the key recording unit 170 records different values for each of the plurality of partial encryption units 450-1 and 450-2.

  FIG. 7 is a configuration diagram of the partial decoding device 500-1 in the maintenance terminal base map update system according to the second embodiment. The partial decryption apparatus 500 has a multi-stage data input unit 510 for inputting encrypted encrypted data and multi-stage encryption conditions (multi-stage decryption conditions), and a multi-stage for outputting encrypted data and multi-stage encryption conditions (multi-stage decryption conditions). A data output unit 520 is provided. Other functions are the same as those of the partial decryption apparatus 200 in the first embodiment. The data input unit 220 inputs the encrypted map data, and whether the next data needs to be decrypted by referring to the decrypted map data. Decoding condition determining unit 230 for determining, decoding condition recording unit 240 for recording the decoding condition, decoding selecting unit 250 for switching necessity of decoding based on the output of the decoding condition determining unit 230, decoding unit 260 for decoding data, decoding A key recording unit 270 that records key information used in the process, a data output unit 280 that outputs decrypted map data, and a data recording unit 290 that records the decrypted data. The data in the data recording unit 290 is output from the multistage data output unit 520 as the encrypted data 320.

  Needless to say, the configuration of partial decoding apparatus 500-2 is substantially the same as that of configuration 1 in FIG.

  FIG. 8 shows the configuration of the multistage encryption condition recording unit 420 in the partial encryption device 400 shown in FIG. In the multistage encryption condition recording unit 420, a plurality of encryption conditions 421 (threshold values) are recorded. The plurality of encryption conditions 421 are listed in descending order from the threshold value with the largest value, and encryption is performed by the partial encryption unit 450 in FIG. 6 in this order, and the partial decryption apparatus 500 in the reverse order. -Decoding by 1 and 2 is performed. Thus, by performing encryption in order from the threshold value with the largest value, the encryption process in the first partial encryption unit 450-1 (that is, the decryption process in the second partial decryption device 500-2 (car navigation system)) is performed. The amount of data to be processed is reduced, and the amount of data to be processed by the encryption process in the second partial encryption unit 450-2 (that is, the decryption process in the first partial decryption device 500-1 (maintenance terminal)) is increased.

  FIG. 9 shows an example of the encrypted data 310 and 320 in FIG. The cipher data 310 describes the first cipher condition 420 and ciphertext, and the data 320 describes the second cipher condition 420 and ciphertext.

  Hereinafter, the operation of the system of the second embodiment will be described along the flow of encryption and decryption processing.

  FIG. 10 shows an example of a setting screen when map data is encrypted using the partial encryption device 400 according to the second embodiment. The setting screen 431 includes a plurality of encryption condition input fields 432 and a key information input field 433 corresponding to each encryption condition. The user of the partial encryption device 400 inputs settings in the encryption condition input field 432 and the key information input field 433 and presses the encryption start button 434. When the encryption start button 434 is pressed, the setting unit 430 sends the input encryption conditions and key information to the multi-stage encryption condition recording unit 420 and the plurality of partial encryption units 450-1 and 450-2 constituting the partial encryption device 400. Set.

  After the setting is made in this way, the partial encryption process in the first embodiment is repeated as many times as the number of multi-stage partial encryption units 450-1 and 450-2. That is, first, the first partial encryption unit 450-1 encrypts data recorded in the data recording unit 410, and the second partial encryption unit 450-2 encrypts the output data.

  After encryption is performed via all the partial encryption units 450-1 and 450-2, the multistage data output unit 440 is combined with the multistage encryption condition 421 recorded in the multistage encryption condition recording unit 420 in the final stage. Output encrypted data.

  Through the above processing, the data is encrypted in multiple stages and recorded on the update DVD 310.

  Hereinafter, data decoding processing in the partial decoding apparatuses 500-1 and 500-2 will be described.

  FIG. 11 is a flowchart showing the operation of the multistage data input unit 510 in the partial decoding apparatuses 500-1 and 500-2. First, the multistage data input unit 510 in FIG. 7 sets the decryption condition in the lowest row among the plurality of encryption conditions (decryption conditions) described in the multistage encryption condition 421 included in the update DVD 310 to the decryption condition recording unit 240. Set (step S511). Next, the remaining encryption conditions (decryption conditions) are output to the data recording unit 290 (step S512). Finally, the encrypted data recorded on the update DVD 310 is input to the data input unit 220 and decrypted.

  The operation until the encrypted data input to the data input unit 220 is decrypted and recorded in the data recording unit 290 is the same as the operation of the partial decryption device 200 in the first embodiment.

  With the above operation, decryption corresponding to the encryption condition (decryption condition) described in the bottom line of the input multi-stage encryption condition 421 is performed. The same applies to the operation of the second partial decoding apparatus 500-2 to which the decoded data is input. At this time, the data input to the second partial decryption device 500-2 is the multistage encryption condition (multistage decryption condition) and decryption recorded in the data recording unit 290 of the first partial decryption device 500-1. Data.

  By the multistage decryption process described above, decryption corresponding to all the encryption conditions described in the multistage encryption condition 421 is performed, and the map data is completely decrypted. That is, the encrypted map data is first decrypted by the dealer's maintenance terminal, and only the minimum data remaining without being decrypted can be decrypted by the car navigation system.

  The present invention described above in detail can be used not only for car navigation map updating but also for general purposes for encrypting large volumes of data.

1 is an overall configuration diagram of a DVD-based map update system according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating an example of map data including XY coordinate data in the first embodiment. FIG. 6 is a flowchart illustrating the operation of an encryption condition determination unit according to the first embodiment. FIG. 6 is a flowchart illustrating the operation of the encryption selection unit according to the first embodiment. FIG. 6 is a schematic explanatory diagram of a maintenance terminal base map update system according to a second embodiment. FIG. 6 is a configuration diagram of a partial encryption device according to a second embodiment. The block diagram of the partial decoding apparatus in Example 2. FIG. FIG. 9 is an explanatory diagram illustrating a configuration of a multistage encryption condition recording unit according to the second embodiment. FIG. 6 is an explanatory diagram illustrating an example of encrypted data in the second embodiment. Explanatory drawing of the screen which sets the multistage encryption conditions in Example 2. FIG. FIG. 9 is a flowchart illustrating the operation of a multistage data input unit according to the second embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Partial encryption apparatus, 130 ... Encryption condition determination part, 150 ... Encryption selection part, 160 ... Encryption part, 200 ... Partial decryption apparatus, 230 ... Decryption condition determination part, 230 ... Decryption selection part, 260 ... Decryption part, 300 ... Update DVD, 400 ... Partial encryption device, 450-1, 2 ... Partial encryption unit, 500-1, 2 ... Partial decryption device.

Claims (15)

A partial decryption device for decrypting encrypted data,
A data input unit for reading the encrypted data;
A decryption unit for decrypting the read encrypted data;
A decryption condition determination unit that determines whether it is necessary to decrypt the subsequent encrypted data with reference to the data decrypted by the decryption unit;
A partial decoding device comprising a data output unit for outputting the decoded data. The partial decoding apparatus according to claim 1, wherein
The partial decryption device, wherein the decryption condition determination unit determines that the subsequent decryption of the encrypted data is necessary when the variation of the decrypted data to be referred to is equal to or greater than a certain threshold. The partial decoding apparatus according to claim 1, wherein
A decoding condition recording unit for storing a decoding condition for determining whether or not decoding is necessary in the decoding unit;
Partial decryption further comprising: a multi-stage data input unit that separates input data into the encrypted data and the decryption conditions, stores the decryption conditions in the decryption condition recording unit, and inputs the encrypted data to the data input unit Device. The partial decoding apparatus according to claim 3, wherein
A partial decoding apparatus further comprising a multi-stage data output unit that outputs the decoded data together with the decoding conditions. A partial encryption device that partially encrypts data,
A data input unit for reading the data;
An encryption condition determination unit that determines whether encryption of the subsequent data is necessary based on the read data and encryption conditions;
An encryption unit that encrypts the data based on the determination result of the encryption condition determination unit;
A partial encryption apparatus comprising: a data output unit that outputs encrypted data encrypted by the encryption unit. The partial encryption apparatus according to claim 5, wherein
A storage unit that stores a threshold value that serves as the encryption condition;
The encryption condition determination unit is a partial encryption device that determines that the subsequent data needs to be encrypted when a variation in the value of the data input from the data input unit is equal to or greater than the threshold. The partial encryption apparatus according to claim 6, wherein
The storage unit stores a plurality of the threshold values,
The encryption unit is composed of a plurality of partial encryption units connected in multiple stages, and each of the plurality of partial encryption units determines whether encryption is necessary by using one of the corresponding plurality of threshold values. Encrypt data,
The data output unit is a partial encryption device that outputs a plurality of the threshold values together with an output of a final stage of the plurality of partial encryption units. A partial decoding method in a decoding device having a processing unit and a storage unit,
The processor is
Read encrypted data,
Decrypting the read encrypted data,
Based on the decrypted data and decryption conditions, determine whether the subsequent encrypted data needs to be decrypted,
A partial decryption method for decrypting subsequent encrypted data based on a determination result of whether or not decryption is necessary. A partial decoding method according to claim 8, comprising:
The storage unit stores a predetermined threshold as the decoding condition,
The processor is
A partial decryption method for determining that subsequent decryption of the encrypted data is necessary when a variation in the value of the decrypted data is equal to or greater than the threshold value. A partial decoding program in a decoding device having a processing unit and a storage unit,
The processing unit is
Decrypt the read encrypted data,
Based on the decrypted data and decryption conditions, determine whether the subsequent encrypted data needs to be decrypted,
A partial decryption program that operates to decrypt subsequent encrypted data based on a determination result of whether or not decryption is necessary. A partial decoding program according to claim 10, wherein
The processing unit is
A partial decryption program that operates to determine that subsequent decryption of the encrypted data is necessary when a change in the value of the decrypted data is equal to or greater than a predetermined threshold stored in the storage unit. A partial encryption method in an encryption device having a processing unit and a storage unit,
The processor is
Based on the read data and encryption conditions, determine whether the subsequent data needs to be encrypted,
A partial encryption method for encrypting the data into encrypted data based on the determination result of whether encryption is necessary, and outputting the encrypted data. The partial encryption method according to claim 12, comprising:
The storage unit stores a predetermined threshold as the encryption condition,
The processor is
A partial encryption method for determining that the subsequent data needs to be encrypted when a variation in the value of the input data is equal to or greater than the threshold. A partial encryption program in an encryption device having a processing unit and a storage unit,
The processing unit is
Based on the read data and encryption conditions, determine whether the subsequent data needs to be encrypted,
A partial encryption program that operates to encrypt the data into encrypted data based on the determination result of the necessity of encryption. The partial encryption program according to claim 14, wherein
The processing unit is
A partial encryption program that operates to determine that the subsequent data needs to be encrypted when a change in the value of the input data is equal to or greater than a predetermined threshold stored in the storage unit.

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