JP2012088991A - Semiconductor memory and computer system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor memory which has high security.SOLUTION: A semiconductor memory 3 includes a storage section 12 in which contents are stored, and a control section 11 which controls access from a host device 2 to the storage section 12. The contents contain a first file which is stored in a first region of the storage section 12, a second file which is stored in a second region of the storage section 12 and is to be read after the first file in normal access, and a third file which is stored in a third region of the storage section 12 and is to be read after the second file in normal access. In the case where the order of access to the first region and the second region is normal, the control section 11 reads the third file from the storage section 12 in response to access to the third region but, in the case where the order of access to the first region and the second region is not normal, does not read the third file from the storage section 12 in response to access to the third region.

Description

  The present invention relates to a semiconductor memory device and a computer system including the same.

  An information processing apparatus in which data stored in a semiconductor memory can be used by an external device by detachably connecting a memory card on which the semiconductor memory is mounted to an external device such as a host computer has been put into practical use. .

  In this type of memory card, a specific security technique is installed in order to prevent data stored in the semiconductor memory from being illegally copied. For example, in Patent Document 1 below, a semiconductor memory in which encrypted data is stored, a detection unit that outputs predetermined key data when addresses are input to the semiconductor memory in a specific order, and reading from the semiconductor memory A semiconductor memory device is disclosed that includes a data conversion unit that decrypts the data using the key data.

JP-A-9-106690

  However, in the semiconductor memory device disclosed in Patent Document 1, there is a possibility that the encryption may be decrypted by analyzing a large number of samples, and there is no restriction on the entire area of the semiconductor memory from the external device. Is accessible. For this reason, once the encryption is decrypted, all data stored in the semiconductor memory is illegally decrypted, so that the security is not sufficient.

  The present invention has been made in view of such circumstances, and an object of the present invention is to obtain a semiconductor storage device having high security and a computer system including the same.

  A semiconductor storage device according to a first aspect of the present invention includes a storage unit in which content is stored, and a control unit that controls access to the storage unit from an external device, and the content is stored in the storage unit. The first file stored in the first area, the second file stored in the second area of the storage unit and read after the first file in normal access, and stored in the third area of the storage unit A third file read after the second file in normal access, and the control unit, when the order of access to the first area and the second area is normal, In response to access to the three areas, the third file is read from the storage unit, and when the access order to the first area and the second area is not normal, the access to the third area is performed. The third file corresponds to Seth is characterized in that no read from the storage unit.

  According to the semiconductor memory device of the first aspect, the control unit stores the third file corresponding to the access to the third area when the order of access to the first area and the second area is not normal. Do not read from storage. Therefore, it is possible to avoid reading the third file from the storage unit due to unauthorized access. Further, since the files included in the content are different for each content, different files can be set for each content as the first file and the second file that are the key to access the third file. Thus, even if a third party who performs unauthorized access breaks security by determining the file access order for a certain content, the third party cannot break the security of other content using the file access order. Therefore, since a third party who performs unauthorized access needs to determine the file access order for each content, the work takes a long time. As a result, it is possible to delay the time when illegally copied products made by unauthorized access are put on the market, and it is possible to protect the genuine products for a long time.

  A semiconductor memory device according to a second aspect of the present invention is the semiconductor memory device according to the first aspect, in particular, the control unit processes an address address that is input from the external device to the semiconductor memory device. A read control unit that reads a file from the storage unit based on a read address input from the address processing unit, and the address processing unit accesses the first area and the second area. If the order is normal, the read address input from the external device to read the third file is converted into a read address indicating the third area, and the first area and the first area are output. If the order of access to the second area is not normal, the read address input from the external device to read the third file is read. And it is characterized in that for converting the read address indicating the different fourth region and the third region.

  According to the semiconductor memory device of the second aspect, the address processing unit is input from an external device to read the third file when the order of access to the first area and the second area is not normal. The read address is converted into a read address indicating a fourth area different from the third area and output. As a result, it is possible to reliably avoid reading the third file from the storage unit due to unauthorized access. In addition, since there is no need to input special instruction codes for the address processing unit from the external device to the semiconductor memory device, a third party who performs unauthorized access analyzes the signals exchanged between the external device and the semiconductor memory device. However, I do not notice the existence of the address processing unit. As a result, it is possible to avoid the content security from being easily broken.

  The semiconductor memory device according to the third aspect of the present invention is the semiconductor memory device according to the first or second aspect, particularly when the order of access to the first area and the second area is normal. However, if the time interval from the access to the first area to the access to the second area is outside a predetermined range, the control unit responds to the access to the third area by The three files are not read from the storage unit.

  According to the semiconductor memory device of the third aspect, even when the order of access to the first area and the second area is normal, the access from the access to the first area to the access to the second area is performed. When the time interval is outside the predetermined range, the control unit does not read the third file from the storage unit in response to the access to the third area. Therefore, even if the file access order is determined, an access whose time interval from the access to the first area to the access to the second area is outside the predetermined range can be identified as an unauthorized access. It is possible to reliably avoid reading the third file from the storage unit.

  The semiconductor memory device according to the fourth aspect of the present invention is normal in the semiconductor memory device according to any one of the first to third aspects, and the order of access to the first area and the second area is normal. Even if there is a case, if the time interval from the access to the second area to the access to the third area is outside the predetermined range, the control unit responds to the access to the third area. Thus, the third file is not read from the storage unit.

  According to the semiconductor memory device of the fourth aspect, even when the order of access to the first area and the second area is normal, from the access to the second area to the access to the third area. When the time interval is outside the predetermined range, the control unit does not read the third file from the storage unit in response to the access to the third area. Therefore, even if the file access order is determined, an access whose time interval from the access to the second area to the access to the third area is outside the predetermined range can be identified as an unauthorized access. It is possible to reliably avoid reading the third file from the storage unit.

  The semiconductor memory device according to a fifth aspect of the present invention is the semiconductor memory device according to any one of the first to fourth aspects, in particular, the content includes a first file including the first file to the third file. And a second file group that includes the first file to the third file and is read after the first file group in normal access, the read-out operation of the second file group with respect to the first area And even when the order of access to the second area is normal, the time interval from the access to the first file group to the access to the second file group is outside a predetermined range. The control unit does not read the third file from the storage unit in response to access to the third area.

  According to the semiconductor memory device of the fifth aspect, with respect to the read operation of the second file group, even if the order of access to the first area and the second area is normal, When the time interval from the access to the access to the second file group is outside the predetermined range, the control unit does not read the third file from the storage unit in response to the access to the third area. Therefore, even if the file access order is determined, an access whose time interval from the access to the first file group to the access to the second file group is outside the predetermined range can be identified as an unauthorized access. It is possible to reliably avoid reading the third file from the storage unit by access.

  The semiconductor memory device according to the sixth aspect of the present invention is the semiconductor memory device according to any one of the second to fifth aspects, particularly in the order of normal access to the first area and the second area. The indicated information is stored in the address processing unit.

  According to the semiconductor memory device of the sixth aspect, information indicating the order of normal access to the first area and the second area (normal access order information) is stored in the address processing unit. Therefore, even when the storage contents of the storage unit are analyzed by a third party who performs unauthorized access, the normal access order information is not stored in the storage unit, so that the normal access order information can be protected. It becomes.

  The semiconductor memory device according to the seventh aspect of the present invention is the semiconductor memory device according to any one of the second to fifth aspects, particularly in the order of normal access to the first area and the second area. The information to be shown is stored in an area having a different access method from the area in which the content is stored in the storage unit.

  According to the semiconductor memory device of the seventh aspect, the information indicating the order of normal access to the first area and the second area (normal access order information) is an area in which content is stored in the storage unit ( The content storage area) is stored in an area having a different access method. Therefore, even when the storage contents of the content storage area are analyzed by a third party who performs unauthorized access, the normal access order information is not stored in the content storage area, so that the normal access order information is protected. Is possible.

  The semiconductor memory device according to the eighth aspect of the present invention is the semiconductor memory device according to any one of the second to seventh aspects, in particular, the object represented by the third file in the fourth region. A fourth file representing an object different from the above is stored.

  According to the semiconductor memory device of the eighth aspect, the fourth file representing the object different from the object represented by the third file is stored in the fourth area. For example, when the third file is airplane image data, the fourth file is set as ship image data. As a result, when a program illegally copied due to unauthorized access is executed, a strange image of the ship flying in the sky will be played, and the user will be aware that the program is an illegal copy. Can do. Further, as compared with the case where measures are taken to stop reading data from the storage unit for unauthorized access, a third party who performs unauthorized access is less likely to notice that the copy has failed. Therefore, since the time to start re-analysis can be delayed, the genuine product can be protected for a long time.

  The semiconductor memory device according to the ninth aspect of the present invention is the semiconductor memory device according to any one of the first to eighth aspects, particularly in the order of normal access to the first area and the second area. The information to be shown is set for each content.

  According to the semiconductor memory device of the ninth aspect, the information indicating the order of normal access to the first area and the second area is set for each content. Therefore, a third party who performs unauthorized access needs to determine the normal access order to the first area and the second area for each content. As a result, it is possible to delay the time when illegally copied products made by unauthorized access are put on the market, and it is possible to protect the genuine products for a long time.

  The semiconductor memory device according to a tenth aspect of the present invention is the semiconductor memory device according to the ninth aspect, in particular, as the first file and the second file, among the plurality of files included in the content, A file in which the order of reading from the storage unit when content is normally reproduced is set is set.

  According to the semiconductor memory device of the tenth aspect, the files in which the reading order from the storage unit when the content is normally reproduced are set as the first file and the second file. Therefore, when the first file and the second file are accessed in the prescribed access order, it is possible to reliably determine that the access order is a normal access order.

  A computer system according to an eleventh aspect of the present invention includes a host device and a semiconductor storage device that can be externally connected to the host device. The semiconductor storage device includes a storage unit that stores content, and an external device. A control unit that controls access to the storage unit from the content, and the content is stored in a first file stored in the first area of the storage unit and a second area of the storage unit, and is normal A second file that is read after the first file in a correct access, and a third file that is stored in the third area of the storage unit and is read after the second file in a normal access, the control unit If the order of access to the first area and the second area is normal, the storage unit stores the third file corresponding to the access to the third area. When the access order to the first area and the second area is not normal, the third file is not read from the storage unit in response to the access to the third area. To do.

  According to the computer system of the eleventh aspect, the control unit stores the third file corresponding to the access to the third area when the order of access to the first area and the second area is not normal. Do not read from part. Therefore, it is possible to avoid reading the third file from the storage unit due to unauthorized access. Further, since the files included in the content are different for each content, different files can be set for each content as the first file and the second file that are the key to access the third file. Thus, even if a third party who performs unauthorized access breaks security by determining the file access order for a certain content, the third party cannot break the security of other content using the file access order. Therefore, since a third party who performs unauthorized access needs to determine the file access order for each content, the work takes a long time. As a result, it is possible to delay the time when illegally copied products made by unauthorized access are put on the market, and it is possible to protect the genuine products for a long time.

  According to the present invention, it is possible to obtain a semiconductor memory device having high security and a computer system including the same.

It is a block diagram which shows the whole structure of the computer system which concerns on embodiment of this invention. It is a block diagram which shows the structure of a control part. It is a block diagram which shows the structure of an address process part. It is a figure which shows a part of storage space of a memory | storage part. It is a figure which shows an example of the preparation procedure of an access order table. It is a figure which shows the 1st process example of an address process part. It is a figure which shows the 2nd process example of an address process part. It is a figure which shows the 3rd processing example of an address process part. It is a block diagram which shows the whole structure of the computer system which concerns on a modification.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the element which attached | subjected the same code | symbol in different drawing shall show the same or corresponding element.

  FIG. 1 is a block diagram showing an overall configuration of a computer system 1 according to an embodiment of the present invention. The computer system 1 includes a host device 2 as an external device and a semiconductor storage device 3 such as a memory card that can be detachably connected to the host device 2. The semiconductor storage device 3 includes a control unit 11 and a storage unit 12. The control unit 11 controls access from the host device 2 to the storage unit 12. The storage unit 12 has a memory cell array, and the storage unit 12 stores arbitrary content such as a program, video, or music. The control unit 11 reads a content file from the storage unit 12 in response to a request from the host device 2 and inputs the read file to the host device 2. Note that the concept of “file” used in this specification includes not only a data group including a plurality of data but also a single data, an instruction code, an instruction function, or the like.

  FIG. 2 is a block diagram illustrating a configuration of the control unit 11. The control unit 11 includes an address processing unit 21 and a read control unit 22. The address processing unit 21 outputs a read address D2 by processing the read address D1 input from the host device 2 to the semiconductor memory device 3. The read control unit 22 generates a control signal D3 based on the read address D2 input from the address processing unit 21, and controls the read operation of the storage unit 12 by the control signal D3. As a result, the file D4 corresponding to the read address D2 is read from the storage unit 12. The read control unit 22 inputs the file D4 read from the storage unit 12 to the host device 2.

  The address processing unit 21 and the read control unit 22 may be formed in the same IC chip or may be formed in separate IC chips. Further, the address processing unit 21, the read control unit 22, and the storage unit 12 may be formed in the same IC chip.

  FIG. 3 is a block diagram showing a configuration of the address processing unit 21. The address processing unit 21 includes a determination unit 31, a storage unit 32, and a timer unit 33. The storage unit 32 stores a table group 40 including an access order table 41, an address conversion table 42, and an access interval table 43.

  FIG. 4 is a diagram illustrating a part of the storage space of the storage unit 12. The storage unit 12 stores a plurality of files F11 to F14 and F21 to F24 included in the content. The files F11, F12, and F13 are stored in the respective storage areas starting from the physical addresses B100, B200, and B300 arranged in this order. The files F21, F22, and F23 are stored in the respective storage areas starting from the physical addresses B400, B500, and B600 arranged in this order. The files F14 and F24 are stored in the respective storage areas starting with the physical addresses B1000 and B1100. Other files may be stored between the files F11, F12, and F13, between the files F13 and F21, between the files F21, F22, and F23, between the files F23 and F14, or between the files F14 and F24.

  The files F11, F12, and F14 belong to the first file group G1 used for reproducing the first scene of the video, for example. The files F21, F22, and F24 belong to the second file group G2 used for reproducing the second scene of the video, for example. Belongs. Here, the files F11, F12, F21, and F22 are files with low confidentiality, and the files F14 and F24 are files to be protected with high confidentiality.

  In the example of the present embodiment, when the host device 2 normally accesses the semiconductor storage device 3 (that is, when it is not unauthorized access), the files F12 → F11 → F14 → F22 → F21 → F24 are sequentially stored from the storage unit 12. Assume that the file is read. That is, the content includes the first file group G1 and the second file group G2 that is read after the first file group G1 in normal access. In particular, regarding the first file group G1, the content is stored in the first file (file F12) stored in the first area of the storage unit 12 (storage area starting from the physical address B200) and the second area of the storage unit 12. The second file (file F11) that is stored in (the storage area starting from the physical address B100) and is read after the first file in normal access, and the third area (the physical address B1000 is the beginning) of the storage unit 12 And a third file (file F14) read after the second file in normal access. Similarly, particularly with respect to the second file group G2, the content is stored in the first file (file F22) stored in the first area of the storage unit 12 (storage area starting with the physical address B500), and in the storage unit 12. A second file (file F21) that is stored in the second area (storage area starting from the physical address B400) and is read after the first file in normal access, and a third area (physical address B1100) of the storage unit 12 And a third file (file F24) that is read after the second file in normal access.

  Specifically, with regard to the first file group G1, among the plurality of files included in the content, the files for which the order of reading from the storage unit 12 when the content is normally played back are determined as the file F12 and the file Set as F11. Preferably, files whose reading order is different from the reading order by sequential access to the storage unit 12 are set as the file F12 and the file F11. Similarly, regarding the second file group G2, among the plurality of files included in the content, files in which the reading order from the storage unit 12 when the content is normally played back are determined as a file F22 and a file F21. Is set. Preferably, files whose reading order is different from the reading order by sequential access to the storage unit 12 are set as the file F22 and the file F21. By setting a file that is not sequential access, when a third party performing unauthorized access attempts to copy the storage contents of the storage unit 12 by sequential dump, it is reliably determined that the access order is not a normal access order. It becomes possible to do.

  Information indicating the normal access order of the files F12 → F11 and the normal access order of the files F22 → F21 is stored as the access order table 41 in the storage unit 32 (see FIG. 3). In the access order table 41, a normal access order is described using a logical address corresponding to a physical address where each file is stored. In the example of the present embodiment, the physical addresses B100, B200, B400, and B500 correspond to the logical addresses A100, A200, A400, and A500, respectively. Accordingly, the access order table 41 describes the normal access order of the logical addresses A200 → A100 and the normal access order of the logical addresses A500 → A400.

  FIG. 5 is a diagram illustrating an example of a procedure for creating the access order table 41 for content including a program. In the source code 50 of the program, a file read command that specifies reading of a file in the order of file F12 → F11 → F14 is described. The content creator first determines the file F14 to be protected by referring to the source code 50, and then arbitrarily selects a plurality of files to be read in that order before the file F14 is read. . In this example, it is assumed that the file F12 and the file F11 are selected. Thereafter, the content creator creates a management table 51 describing the file names of the selected file F12 and file F11 and the access order to these files. When the source code 50 is created, a management table 51 is automatically created by a compiler or the like by adding a special description including designation of the access order to each file read instruction of the file F12 and the file F11. Also good.

  Thereafter, the access order table 41 is created by encoding the management table 51 by a converter or the like. In this example, the access order table 41 describes logical addresses A200 to A203 corresponding to the file F12 and logical addresses A100 to A103 corresponding to the file F11 according to the access order.

  In the above example, the content creator selects the file F12 and the file F11 from the source code 50. However, when the selected file is different, the description contents of the access order table 41 are also different. Therefore, various access order tables 41 can be created by intentionally different files to be selected even for the same content. Also, the files included in the content are usually different for each content. Therefore, the files selected for different contents are different, and as a result, the description contents of the access order table 41 are also different. That is, since the description contents of the access order table 41 differ depending on the contents, the description contents of the access order table 41 are set for each content.

  Referring to FIG. 4, files F13 and F23 are dummy files related to files F14 and F24, respectively. The files F13 and F23 store data representing objects different from the objects represented by the files F14 and F24. For example, data representing objects of the same type but different types from the objects represented by the files F14 and F24 are stored in the files F13 and F23. As an example, when airplane image data is stored in the files F14 and F24, the ship image data is stored in the files F13 and F23. Airplanes and ships have the same attributes as vehicles, but are of different types. Note that the data stored in the files F13 and F23 may be some trap code or a program or data for warning the user of unauthorized access. For example, image data or audio data representing a warning message such as “This memory is illegally copied” may be stored in the files F13 and F23.

  Hereinafter, the operation of the address processing unit 21 will be described.

  FIG. 6 is a diagram illustrating a first processing example of the address processing unit 21. Here, processing when unauthorized access is performed is shown. When a third party performing unauthorized access attempts to copy the storage contents of the storage unit 32 by sequential dump, as shown in FIG. 6A, logical addresses A100 → A200 → A300 → A400 → A500 → A600 In this order, the read address D1 is input to the address processing unit 21.

  Referring to FIG. 3, determination unit 31 refers to access order table 41 to determine that the input order of logical addresses A100 → A200 → A300 → A400 → A500 → A600 is not a normal access order.

  The storage unit 32 stores, as the address conversion table 42, a table used when the determination unit 31 determines unauthorized access and a table used when the determination unit 31 determines normal access. In this example, the determination unit 31 refers to the former table, and as shown in FIG. 6B, the logical addresses A100, A200, A300, A400, A500, A600 are changed to the physical addresses B100, B200. , B300, B400, B500, and B600, respectively. As a result, as shown in FIG. 6C, the file is read from the storage unit 12 in the order of the file F11 → F12 → F13 → F21 → F22 → F23. The files F14 and F24 are protected by reading the dummy files F13 and F23 instead of the files F14 and F24 to be protected.

  FIG. 7 is a diagram illustrating a second processing example of the address processing unit 21. Here, the processing when a normal access is performed is shown. When the host device 2 normally accesses the semiconductor memory device 3, as shown in FIG. 7A, the read address D1 is processed in the order of logical addresses A200 → A100 → A300 → A500 → A400 → A600. Input to the unit 21.

  With reference to FIG. 3, the determination unit 31 determines that the input order of the logical addresses A200 → A100 → A300 → A500 → A400 → A600 is a normal access order by referring to the access order table 41.

  As described above, the storage unit 32 stores, as the address conversion table 42, a table used when the determination unit 31 determines unauthorized access and a table used when the determination unit 31 determines normal access. ing. In this example, the determination unit 31 refers to the latter table, so that the logical addresses A200, A100, A300, A500, A400, and A600 are assigned to the physical addresses B200 and B100 as shown in FIG. , B1000, B500, B400, and B1100, respectively. As a result, as shown in FIG. 7C, the file is read from the storage unit 12 in the order of the file F12 → F11 → F14 → F22 → F21 → F24. By reading the protected files F14 and F24 instead of the dummy files F13 and F23, the content is normally played back on the host device 2.

  Even if the determination unit 31 once determines that the access is normal, when the content is read from the storage unit 12 again, the determination unit 31 determines whether the access is normal again. Execute. That is, every time content is read from the storage unit 12, the determination by the determination unit 31 is executed.

  FIG. 8 is a diagram illustrating a third processing example of the address processing unit 21. As shown in FIG. 8A, the read address D1 is input to the address processing unit 21 in the order of logical addresses A200 → A100 → A300 → A500 → A400 → A600.

  With reference to FIG. 3, the determination unit 31 determines that the input order of the logical addresses A200 → A100 → A300 → A500 → A400 → A600 is a normal access order by referring to the access order table 41.

  The storage unit 32 stores an access interval table 43. In the access interval table 43, set values T11, T12, T13, T21, and T22 representing normal ranges (upper limit value, lower limit value, or both) related to the access time interval are described. As the set values T11, T12, T13, T21, and T22, appropriate values are set in advance based on the time required to reproduce each scene of the content.

  As the set value T11, the normal range of the time interval from the input of the logical address A200 to the input of the logical address A100 in normal access is set. That is, the normal range of the time interval from the start of access to the file F12 to the start of access to the file F11 is set in normal access.

  Similarly, as the setting values T12, T21, and T22, normal ranges of time intervals from the input of the logical addresses A100, A500, and A400 to the input of the logical addresses A300, A400, and A600 in normal access are set. ing. That is, the normal ranges of the time intervals from the start of access to the files F11, F22, and F21 to the start of access to the files F14, F21, and F24 are set.

  As the set value T13, the normal range of the time interval from the input of the logical address A200 to the input of the logical address A500 in normal access is set. That is, the normal range of the time interval from the start of access to the first file group G1 to the start of access to the second file group G2 is set in normal access.

  The determination unit 31 determines that the access is normal when the access order is normal and the access time interval is within the normal range.

  Specifically, for the first file group G1, the determination unit 31 inputs the logical addresses in the order of logical addresses A200 → A100 → A300, and the logical address A100 is input after the logical address A200 is input. When the time interval until the input is within the range of the set value T11 and the time interval from the input of the logical address A100 to the input of the logical address A300 is within the range of the set value T12 Determine access. On the other hand, if any one of the above conditions is not satisfied, the determination unit 31 determines that the access is unauthorized. The determination unit 31 measures the access time interval based on the time count value input from the time measuring unit 33.

  In addition, regarding the second file group G2, the determination unit 31 inputs the logical addresses in the order of logical addresses A500 → A400 → A600, and the logical address A500 is input after the logical address A200 is input. The time interval from the input of the logical address A500 to the input of the logical address A400 is within the range of the set value T21, and the logical address A400 When the time interval from the input of the logical address A600 to the input of the logical address A600 is within the set value T22, it is determined that the access is normal. On the other hand, if any one of the above conditions is not satisfied, the determination unit 31 determines that the access is unauthorized.

  In addition, as described above, the storage unit 32 includes, as the address conversion table 42, a table used when the determination unit 31 determines unauthorized access and a table used when the determination unit 31 determines normal access. It is remembered. The determination unit 31 refers to the former table when determining that the access is unauthorized. As a result, the dummy files F13 and F23 are read instead of the protection target files F14 and F24. On the other hand, when the determination unit 31 determines that the access is normal, the determination unit 31 refers to the latter table. Thereby, the files F14 and F24 to be protected are read out instead of the dummy files F13 and F23. 8B and 8C show processing when the determination unit 31 determines normal access.

  FIG. 9 is a block diagram showing an overall configuration of a computer system 1 according to a modification of the present embodiment. In the above description, the table group 40 is stored in the address processing unit 21, but the table group 40 may be stored in the storage unit 12. When the host device 2 is powered on, the control unit 11 reads the table group 40 from the storage unit 12 and stores it in an internal register or the like. As a result, the determination unit 31 can refer to the table group 40. In the present modification, it is desirable to store the table group 40 in a storage area that has a different access method from the storage area in which the content is stored. For example, the storage unit 12 having a plurality of memory banks is employed, and the table group 40 is stored in a memory bank different from the memory bank in which the content is stored. Alternatively, different buses are used for the bus for accessing the contents and the bus for accessing the table group 40.

  As another modification, in the above description, the two files F12 and F11 are used as files serving as a key for accessing the file F14. However, three or more files may be used. The same applies to the second file group G2.

  As described above, according to the semiconductor storage device 3 according to the present embodiment, the control unit 11 determines that the storage area of the file F14 when the order of access to the storage area of the file F12 and the storage area of the file F11 is not normal. The file F14 is not read from the storage unit 12 in response to the access to. Therefore, it is possible to avoid reading the file F14 from the storage unit 12 due to unauthorized access. In addition, since the files included in the content are different for each content, different files can be set for each content as the file F12 and the file F11 which are keys for accessing the file F14. Thus, even if a third party who performs unauthorized access breaks security by determining the file access order for a certain content, the third party cannot break the security of other content using the file access order. Therefore, since a third party who performs unauthorized access needs to determine the file access order for each content, the work takes a long time. As a result, it is possible to delay the time when illegally copied products made by unauthorized access are put on the market, and it is possible to protect the genuine products for a long time.

  Further, according to the semiconductor storage device 3 according to the present embodiment, as shown in FIG. 7, the address processing unit 21 does not have a normal order of access to the storage area of the file F12 and the storage area of the file F11. The logical address A300 input from the host device 2 for reading the file F14 is converted into a physical address B300 indicating a storage area (fourth area) of the file F13 different from the storage area of the file F14 and output. . Thereby, it is possible to reliably avoid reading the file F14 from the storage unit 12 due to unauthorized access. In addition, since it is not necessary to input a special instruction code for the address processing unit 21 from the host device 2 to the semiconductor memory device 3, a third party who performs unauthorized access is exchanged between the host device 2 and the semiconductor memory device 3. Even if the received signal is analyzed, the presence of the address processing unit 21 is not noticed. As a result, it is possible to avoid the content security from being easily broken.

  Further, according to the semiconductor memory device 3 according to the present embodiment, as shown in FIG. 8, even when the access order to the storage area of the file F12 and the storage area of the file F11 is normal, When the time interval from the access to the storage area of the file F12 to the access to the storage area of the file F11 is outside the range of the set value T11, the control unit 11 responds to the access to the storage area of the file F14. Thus, the file F14 is not read from the storage unit 12. Therefore, even if the file access order is determined, an access in which the time interval from the access to the storage area of the file F12 to the access to the storage area of the file F11 is outside the set value T11 is identified as an unauthorized access. Therefore, it is possible to reliably avoid reading the file F14 from the storage unit 12 due to the unauthorized access.

  Further, according to the semiconductor memory device 3 according to the present embodiment, as shown in FIG. 8, even when the access order to the storage area of the file F12 and the storage area of the file F11 is normal, When the time interval from the access to the storage area of the file F11 to the access to the storage area of the file F14 is outside the set value T12, the control unit 11 responds to the access to the storage area of the file F14. Thus, the file F14 is not read from the storage unit 12. Therefore, even if the file access order is determined, an access in which the time interval from the access to the storage area of the file F11 to the access to the storage area of the file F14 is outside the set value T12 is identified as an unauthorized access. Therefore, it is possible to reliably avoid reading the file F14 from the storage unit 12 due to the unauthorized access.

  Further, according to the semiconductor memory device 3 according to the present embodiment, as shown in FIG. 8, the order of access to the storage area of the file F22 and the storage area of the file F21 regarding the read operation of the second file group G2. Is normal, if the time interval from the access to the first file group G1 to the access to the second file group G2 is outside the set value T13, the control unit 11 Corresponding to the access to the storage area of F24, the file F24 is not read from the storage unit 12. Therefore, even if the file access order is determined, an access in which the time interval from the access to the first file group G1 to the access to the second file group G2 is outside the range of the set value T13 is identified as an unauthorized access. Therefore, it is possible to reliably avoid reading the file F24 from the storage unit 12 due to the unauthorized access.

  Further, according to the semiconductor storage device 3 according to the present embodiment, as shown in FIG. 3, information indicating the order of normal access to the storage area of the file F12 and the storage area of the file F11 (access order table 41). ) Is stored in the address processing unit 21. Therefore, even when the storage content of the storage unit 12 is analyzed by a third party who performs unauthorized access, the access order table 41 is not stored in the storage unit 12, and thus the access order table 41 is protected. Is possible.

  Further, according to the modification shown in FIG. 9, information (access order table 41) indicating the order of normal access to the storage area of the file F <b> 12 and the storage area of the file F <b> 11 is stored in the storage unit 12. The storage area (content storage area) is stored in an area having a different access method. Therefore, even when the storage contents of the content storage area are analyzed by a third party who performs unauthorized access, the access order table 41 is not stored in the content storage area, and thus the access order table 41 is protected. Is possible.

  Further, according to the semiconductor memory device 3 according to the present embodiment, the file F13 representing the object different from the object represented by the file F14 is stored in the storage area (fourth area) starting with the physical address B300. Is remembered. For example, when the file F14 is airplane image data, the file F13 is used as ship image data. As a result, when a program illegally copied due to unauthorized access is executed, a strange image of the ship flying in the sky will be played, and the user will be aware that the program is an illegal copy. Can do. Further, as compared with the case where measures are taken to stop reading data from the storage unit 12 for unauthorized access, a third party who performs unauthorized access is less likely to notice that copying has failed. Therefore, since the time to start re-analysis can be delayed, the genuine product can be protected for a long time.

  Further, according to the semiconductor storage device 3 according to the present embodiment, the information indicating the order of normal access to the storage area of the file F12 and the storage area of the file F11 (access order table 41) is set for each content. . Therefore, a third party who performs unauthorized access needs to determine the normal access order to the file F12 and the file F11 for each content. As a result, it is possible to delay the time when illegally copied products made by unauthorized access are put on the market, and it is possible to protect the genuine products for a long time.

  In addition, according to the semiconductor storage device 3 according to the present embodiment, files in which the order of reading from the storage unit 12 when content is normally reproduced are set as the file F12 and the file F11. Therefore, when the file F12 and the file F11 are accessed in the prescribed access order, it is possible to reliably determine that the access order is a normal access order.

DESCRIPTION OF SYMBOLS 1 Computer system 2 Host apparatus 3 Semiconductor memory device 11 Control part 12 Memory | storage part 21 Address processing part 22 Read control part 31 Determination part 41 Access order table 42 Address conversion table 43 Access interval table

Claims (11)

A storage unit in which content is stored;
A control unit for controlling access to the storage unit from an external device;
With
The content is
A first file stored in a first area of the storage unit;
A second file stored in the second area of the storage unit and read after the first file in normal access;
A third file stored in the third area of the storage unit and read after the second file in normal access;
Including
The controller is
When the order of access to the first area and the second area is normal, the third file is read from the storage unit corresponding to the access to the third area,
A semiconductor memory device in which the third file is not read from the storage unit in response to the access to the third area when the order of access to the first area and the second area is not normal. The controller is
An address processing unit for processing a read address input from the external device to the semiconductor memory device;
A read control unit that reads a file from the storage unit based on a read address input from the address processing unit;
Have
The address processing unit
If the order of access to the first area and the second area is normal, the read address input from the external device for reading the third file is used as a read address indicating the third area. Convert and output,
If the order of access to the first area and the second area is not normal, a read address input from the external device for reading the third file is set to a fourth area different from the third area. The semiconductor memory device according to claim 1, wherein the read address is converted into a read address and output.   Even when the order of access to the first area and the second area is normal, the time interval from the access to the first area to the access to the second area is outside the predetermined range The semiconductor memory device according to claim 1, wherein the control unit does not read the third file from the storage unit in response to access to the third area.   Even when the order of access to the first area and the second area is normal, the time interval from the access to the second area to the access to the third area is outside a predetermined range The semiconductor memory device according to claim 1, wherein the control unit does not read the third file from the storage unit in response to access to the third area. The content is
A first file group including the first to third files;
A second file group that includes the first file to the third file and is read after the first file group in normal access;
Including
Regarding the read operation of the second file group, even if the order of access to the first area and the second area is normal, the access from the first file group to the second file group The control unit does not read the third file from the storage unit in response to access to the third area when a time interval until access is outside a predetermined range. A semiconductor memory device according to claim 1.   6. The semiconductor memory device according to claim 2, wherein information indicating an order of normal access to the first area and the second area is stored in the address processing unit.   The information indicating the order of normal access to the first area and the second area is stored in an area having a different access method from the area in which the content is stored in the storage unit. The semiconductor memory device according to any one of 2 to 5.   The semiconductor memory device according to claim 2, wherein a fourth file representing an object different from the object represented by the third file is stored in the fourth area.   9. The semiconductor memory device according to claim 1, wherein information indicating a normal access order to the first area and the second area is set for each content.   As the first file and the second file, among the plurality of files included in the content, a file in which the reading order from the storage unit when the content is normally reproduced is set, The semiconductor memory device according to claim 9. A host device,
A semiconductor storage device externally connectable to the host device;
With
The semiconductor memory device
A storage unit in which content is stored;
A control unit for controlling access to the storage unit from an external device;
Have
The content is
A first file stored in a first area of the storage unit;
A second file stored in the second area of the storage unit and read after the first file in normal access;
A third file stored in the third area of the storage unit and read after the second file in normal access;
Including
The controller is
When the order of access to the first area and the second area is normal, the third file is read from the storage unit corresponding to the access to the third area,
A computer system that does not read the third file from the storage unit in response to the access to the third area when the order of access to the first area and the second area is not normal.

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