JP2005275654A - Semiconductor memory device - Google Patents

Abstract

In a semiconductor memory device having a copyright protection function, both protection function enhancement and high-speed recording are compatible.
In order to increase the frequency of mutual authentication performed together with transmission / recording of contents from a host device to a semiconductor memory device, a nonvolatile memory such as a ferroelectric memory capable of higher-speed writing than a flash memory is provided. . A flash memory 113 is used as the main memory of the semiconductor memory device 119. Since the content protection information (title key management information 106 and title key 107) that is updated and recorded at the time of mutual authentication is recorded in the nonvolatile memory 105, even if the frequency of mutual authentication is increased to enhance content protection, The time overhead required for updating and recording the content protection information can be reduced, and as a result, the enhancement of the content protection function and high-speed recording can both be achieved.
[Selection] Figure 1

Description

  The present invention relates to a semiconductor memory device having a copyright protection function for data recorded in a nonvolatile memory.

  With the rise of semiconductor memory devices typified by memory cards, various optical discs typified by DVDs (Digital Versatile Discs), and network-type content distribution businesses typified by Internet technologies, protection against digital content handled here As a method, a more advanced copyright protection method using encryption technology has come to be adopted. Among them, a semiconductor memory device (for example, an SD memory card) adopting a CPRM (Content Protection for Recordable Media) method, a storage device such as a DVD, a music recording / reproducing device, a still image recording / reproducing device, a moving image, Recording / reproducing devices and the like are widely accepted in the market.

  CPRM is an unauthorized copy prohibition function using a common key encryption, and an ID (identification information) is provided in the storage device and / or recording / playback device (hereinafter referred to as a host device), or both, and an encryption key corresponding to the ID is used. The content is encrypted and recorded in the storage device. Even if the encrypted content is copied to another storage device, the ID assigned to the storage device is different, so that the correct decryption is not performed and the content cannot be reproduced. In other words, when the information embedded in the digital content storage device and the host device matches the usage conditions of the content, the storage device determines whether or not protection functions effectively. Or it depends on the content protection power of the host device. As further advanced network society progresses in the future, further enhancement of content protection is desired.

  Here, a mechanism in which the CPRM content protection technology is applied to an SD memory card will be described below (refer to Non-Patent Document 1 for details). CPRM not only strengthens conventional protection technologies (eg, CSS: Content Scramble System), but also supports stronger copyright protection that supports the function of disabling encryption keys if they are leaked. Technology. The content recorded on the SD memory card is encrypted and uses the device key (device key) held on the host device side and the MKB (Media Key Block) recorded on the SD memory card side during playback. Generate a “media key” necessary for decrypting the content, decrypt the content, and play it. As a specific mechanism, recorded content is encrypted using a key created from three pieces of information: a media key and a title key that is different in units of titles, and CCI (Copy Control Information).

  As described above, the media key can be generated using a device key and an MKB described later. The title key is recorded in a protected area in the SD memory card and cannot be copied. Similarly, the MKB necessary for generating the media key is also recorded in the system area, and this cannot be duplicated or altered. Further, the MKB is not only distributed to the manufacturer by the license company, but also the maximum number is determined. For this reason, a unique one is not always used, and when it reaches a certain number, it is updated to a new one.

  CCI is information related to replication. Not only information indicating whether copying is possible, but also information indicating how many times copying is permitted when copying is permitted. The CCI is always recorded together with the content, and the same applies when copying. For example, if a piece of content that can be copied only once is copied into the information that “replication is impossible”, the copied medium can be properly copied. It is also possible to perform detailed control such as how many generations are allowed to be copied.

  The device key prepared on the host device side is a key given from the license company to the host device manufacturer. Different ones are always used for each host device, and the same key is not used. When used on a PC (personal computer), software used for reproduction corresponds to a “host device”. This is because the PC drive does not have a function for determining what kind of data it is. In the PC, the software authenticates the drive and the medium through confidential communication.

  In this way, CPPM is composed of four pieces of information such as MKB, title key, CCI, and device key. Actual content playback uses the MKB and device key to generate a media key, and then the title key and CCI. Playback is performed in a procedure of generating a “key” used for encryption using. Therefore, the content cannot be restored if any one of the four pieces of information is incorrect. Also, when recording content on an SD memory card, the title key is transmitted along with the encrypted content on the bus, but the title key may be decrypted, so a time-varying key (session key) ) Has been introduced to encrypt the title key. The session key for encryption is changed with time, and the encrypted title key is mutually authenticated each time the session key is changed, and is updated and recorded on the SD memory card each time (rewrite) ). The content protection information described above is recorded in the system area, the secret area, and the protection area of the SD memory card, and is physically recorded in the mask ROM and the flash memory as shown in FIG. Note that the secret area and the protection area described here correspond to the Hidden area and the protection area of Patent Document 1, respectively.

In addition to the CPRM described above, a method as shown in Patent Document 2 is disclosed as a copyright protection method involving mutual authentication. In this method, the encryption key is updated and recorded in the flash memory or the like during mutual authentication.
Japanese Patent Laying-Open No. 2002-206467 (FIG. 14) JP 2001-243707 A (see, for example, paragraph 0092) “SD Memory Card Standards and Copyright Protection Technology”, Hisao Sakamoto et al., Matsushita Technical Journal, Vol. 48, No. 2, pages 4-10, April 2002, Matsushita Electric Industrial Co., Ltd. R & D Planning Office Co., Ltd. issued

  However, with further progress of the network society in the future and with the evolution of digital data transmission technology, semiconductor technology and signal processing technology, further enhancement of content protection function is desired. As a method for strengthening the content protection function, it is conceivable to increase the frequency of mutual authentication between the host device and the recording medium. As a result, the content protection function is strengthened. However, since the frequency of processing for that purpose, particularly the access to the recording medium, increases, there is a possibility that the reading / writing speed of the recording medium may be reduced. This is contrary to high-speed recording, which is the desired performance.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described conventional problems, and to provide a semiconductor memory device that can achieve both enhancement of a content protection function and high-speed recording.

  To achieve this object, a semiconductor memory device according to the present invention includes a nonvolatile memory that records at least content data, a nonvolatile RAM that stores content protection information that is updated and recorded at least during mutual authentication, a nonvolatile memory, and a nonvolatile memory. A nonvolatile memory control unit that performs access control to the nonvolatile RAM, and the nonvolatile RAM has a higher rewrite speed in at least a small data unit than the nonvolatile memory. As a result, in the processing related to mutual authentication, the time overhead required for the update recording of the content protection information can be reduced, and as a result, the enhancement of the content protection function and the high speed recording can both be achieved.

  According to the present invention, the content protection information to be updated and recorded at the time of mutual authentication is stored in the nonvolatile RAM that can be rewritten at a higher speed than the nonvolatile memory (for example, flash memory) as the main memory. Thus, it is possible to achieve both enhancement of the content protection function by increasing the frequency of mutual authentication (that is, the update frequency of the content protection information) and high-speed rewriting of the content protection information.

  The invention according to claim 1 of the present invention includes a nonvolatile memory that records at least content data, a nonvolatile RAM that stores content protection information that is updated and recorded at least during mutual authentication, and the nonvolatile memory and the nonvolatile RAM. A non-volatile memory control unit that performs access control of the non-volatile memory, wherein the non-volatile RAM has a higher rewrite speed in units of at least smaller data than the non-volatile memory. . This makes it possible to achieve both enhancement of the content protection function by increasing the frequency of mutual authentication (that is, the update frequency of the content protection information) and high-speed rewriting of the content protection information.

  According to a second aspect of the present invention, in the first aspect of the present invention, the nonvolatile RAM, the nonvolatile memory control unit, and the semiconductor integrated circuit are configured as one semiconductor integrated circuit. Make it unobservable.

  According to a third aspect of the present invention, in the second aspect of the invention, the non-volatile RAM is arranged in a distributed manner on the semiconductor integrated circuit, and the non-volatile RAM is observed from the surface of the LSI. It is possible to make it difficult to specify the recorded contents.

  The invention according to claim 4 of the present invention is the invention according to any one of claims 1 to 3, wherein the nonvolatile RAM is a ferroelectric memory (FeRAM).

  The invention according to claim 5 of the present invention is the invention according to any one of claims 1 to 3, wherein the non-volatile RAM is a magnetic recording type random write / read memory (MRAM). .

  The invention according to claim 6 of the present invention is characterized in that, in the invention according to any one of claims 1 to 3, the nonvolatile RAM is an ovonic unified memory (OUM).

  The invention according to claim 7 of the present invention is the invention according to any one of claims 1 to 3, wherein the nonvolatile RAM is a resistance RAM (RRAM).

  According to the inventions according to the fourth to seventh aspects, since all can be rewritten faster than the flash memory, the content protection function can be enhanced by increasing the frequency of mutual authentication (that is, the update frequency of the content protection information). It is possible to achieve both high-speed rewriting of content protection information.

  Hereinafter, semiconductor memory devices according to embodiments of the present invention will be described with reference to the drawings.

(Embodiment)
FIG. 1 is a block diagram showing a method for implementing a semiconductor memory device according to an embodiment of the present invention. In the present embodiment, a copyright protection method (specifically, the above-described CPRM method) for performing update recording of content protection information at the time of mutual authentication is described as an example, and the invention is particularly applied to the CPRM method. It is not limited.

  In FIG. 1, 119 is a semiconductor memory device, and 100 is a host device that performs read / write access to the semiconductor memory device 119. In the semiconductor memory device 119, 112 is a control unit configured as a control LSI, and 113 is a flash memory as a nonvolatile memory.

  In the controller unit 112, 101 is a host I / F unit that is an interface with the host device 100, 102 is a CPU that controls the entire controller unit 112, 103 is a work RAM of the CPU 102, and 104 is a program executed by the CPU 102. , 105 is a nonvolatile RAM, 106 is a title key management information stored in the nonvolatile RAM 105, 107 is a title key stored in the nonvolatile RAM 105, 108 is an address management information control unit, and 109 is a flash memory 113. In addition, a nonvolatile memory control unit that performs access control of the nonvolatile RAM 105, 110 is a volatile RAM, and 111 is address management information stored in the volatile RAM 110.

  In the flash memory 113, 114 is key revocation information, 115 is a media ID, 116 is a media unique key, 117 is encrypted content, and 118 is unencrypted content, which are data stored in the flash memory 113.

  FIG. 2 shows a copyright protection mechanism in electronic music distribution using the semiconductor memory device in this embodiment (total copyright protection mechanism and CPRM mechanism taking electronic music distribution over the Internet as an example). It is a schematic diagram. 201 is a provider that supplies content, 202 is a host device (recording side), 203 is a memory card (corresponding to the semiconductor memory device 119 in this embodiment), and 204 is a host device (playback side).

  The operation of the semiconductor memory device 119 configured as described above will be described below.

  First, a basic operation of the semiconductor memory device 119 will be described with reference to FIG. 1 (operation for writing unencrypted content 118, omitting the operation of copyright protection such as mutual authentication for the sake of simplicity), and FIG. The mechanism of copyright protection in electronic music distribution will be described with reference to the total mechanism of copyright protection and the mechanism of CPRM taking electronic music distribution over the Internet as an example. Finally, the contents of the present invention will be described with reference to FIG. explain.

  First, in FIG. 1, after the host device 100 is powered on, an initialization operation in the semiconductor memory device 119 is started in accordance with an initialization command transferred from the host device 100. The CPU 102 executes an initialization program stored in the ROM 104, examines the recording state of various data recorded in the flash memory 113, and converts the logical-physical address table to convert the logical address into a physical address on the volatile RAM 110. Address management information 111 is constructed. Thereafter, the controller unit 112 enters a state of waiting for access from the host device 100. When the write command, data, and logical address are transferred from the host device 100 to the semiconductor memory device 119, the semiconductor memory device 119 transfers the data to the flash memory 113 via the host I / F unit 101 and the nonvolatile memory control unit 109. Go to writing. At this time, the address management information control unit 108 uses the host device 100 based on the address management information 111 stored in the volatile RAM 110 so that the concentration of writing does not occur at the specific physical address of the flash memory 113 (for wear leveling). Is converted into a physical address of the flash memory 113, and data is written to the physical address. The non-volatile memory (flash memory 113 and non-volatile RAM 105) forms one logical space (system area, secret area, data area, protection area), and the data is data (that is, various contents) in the logical space. And various key information).

  Next, a copyright protection mechanism in electronic music distribution (a total mechanism of copyright protection and a CPRM mechanism taking electronic music distribution over the Internet as an example) will be described with reference to FIG. The SD memory card has a CPRM specification that supports not only music but also various applications such as images and voices. Here, a music application (audio application) will be described as an example.

1. Mechanism of copyright protection in electronic music distribution (1) Download of music content Music content is downloaded to the user's PC (host device (recording side) 202) via the Internet. At this time, the content is protected by encryption (network encryption) based on the electronic distribution mechanism. This mechanism is outside the scope of CPRM.

(2) Content storage in SD memory card The software on the PC and the memory card 203 mutually authenticate based on the CPRM mechanism and confirm the validity of each. Thereafter, the software on the PC encrypts the music content (C2 encryption) and stores it on the card.

(3) Playback by SD Audio Player The SD memory card and the SD audio player (host device (playback side) 204) authenticate each other and confirm their validity based on the CPRM mechanism. Thereafter, the player decrypts (C2 decryption) the encrypted content read from the card and reproduces it.

2. CPRM mechanism Next, the CPRM mechanism will be described in more detail. The following numbers A to D correspond to the reference numerals shown in FIG.

A) MKB Processing A unique device key is assigned to each device for a regular device (software on the PC and SD audio player) that accesses the SD memory card. On the other hand, in the SD memory card, data called MKB (Media Key Block) is recorded in the system area. A legitimate device acquires the correct media key by processing the MKB using this device key.

B) Media ID and Media Unique Key In the SD memory card, a media ID and a media unique key unique to each card are recorded in the system area and a secret area that cannot be read or written from outside. The legitimate device acquires the media unique key from the media key acquired by the MKB process of A) and the media ID.

C) Mutual authentication The authorized device and the SD memory card mutually authenticate using the media unique key.

D) Content encryption A legitimate device stores a title key (and copy control information, etc.) encrypted using a media unique key in a protected area accessible only when the mutual authentication of C) is successful. The content encrypted using the title key is stored in an arbitrarily accessible data area. Here, C2 encryption (Cryptomeria Cipher) is used for encryption. The C2 cipher has the feature that, while ensuring high security strength, the realization scale and power consumption can be reduced with hardware implementation, and high-speed processing is possible with software implementation.

3. Regarding the security of CPRM (1) Secure communication The mutual authentication of C) described above is executed each time when a random number is generated, and the data such as the encrypted title key read and written in the protected area in D) is the result of mutual authentication. Using a shared time variable key (session key), the data is further encrypted and securely transferred.

(2) Unauthorized copy prevention The encrypted content body stored in the data area can be freely copied to other recording media by the mechanism of D) above, but the title key stored in the protected area is illegally copied. Can not. Therefore, as a result, reproduction cannot be performed and unauthorized copying is prevented. In addition, even if the encrypted title key stored in the protected area is copied by some method, the title key is encrypted with a unique media unique key for each card and cannot be decrypted with other recording media. .

(3) Revocation (key revocation)
In the mechanism of A) above, if a device key of a certain device is revealed and unauthorized copy software using that device key is distributed, the device and the unauthorized copy software for which the device key has been exposed are New MKB data is issued and recorded on the SD memory card so that the correct media key is not obtained even if the MKB is processed using the device key. By this mechanism, the device whose device key has been exposed and the disseminated unauthorized copy software cannot be processed correctly (invalidated) in combination with an SD memory card in which a new MKB is recorded.

  Finally, the contents of the present invention will be described with reference to FIGS. The semiconductor memory device 119 of the present invention employs content protection (copyright protection) based on CPRM as described above. As a method for further strengthening content protection based on CPRM, it is conceivable to increase the frequency of mutual authentication. Increasing the frequency of mutual authentication means the update frequency of the time-varying key (session key), that is, the title key transferred together with the content from the host device 100 in FIG. 1 (nonvolatile RAM 105 in FIG. 1, ie, protected area It is equivalent to increasing the update frequency of the content protection information recorded and updated in (1). Such information includes, for example, the title key shown in FIG. 3 (the key corresponding to each piece of music, EKEY [0... 55]) and title key management information (not shown).

  As shown in FIG. 3, the title key includes a title key body (EKEY, 7 bytes), copy control information (CCI, 2 bits), a title key validity flag (Availability flag, 1 bit), a content ID (Content ID, 10 bits) ), And the rest consists of a total of 16 bytes in the reserved area (Reserved). The title key management information is also 16 bytes (details are omitted). The above 32-byte information (hereinafter referred to as title key information, etc.) is content protection information corresponding to one piece of music (recorded and updated in the protection area), and if the frequency of mutual authentication is increased, The recording update frequency of title key information and the like increases. That is, if the content protection is strengthened, the time overhead required for recording / updating the title key information and the like increases, and as a result, the access speed decreases. Conventionally, since the title key information and the like have been recorded and updated in the flash memory, this time overhead required approximately 1 ms for each update (see the write cycle time in FIG. 4). The update frequency of mutual authentication per song is a matter of implementation. In conventional products, for example, in content recording per song, title key information and the like have been updated and recorded once. The update overhead time for the title key information and the like per song requires about 1 ms. In order to strengthen security protection in the future, if the update frequency of the title key information is performed 100 times per song, for example, 1 ms × 100 times = 100 ms, and the time overhead in updating the title key information etc. Is 100 ms. As a result, the degradation in access speed is greater than in the prior art. Furthermore, since the flash memory has a guaranteed number of rewrites of about 100,000 times, it is preferable in terms of the life of the flash memory, that is, the life of the SD memory card, if the authentication update frequency is increased too much compared to the ferroelectric memory. Absent.

  On the other hand, in the semiconductor memory device 109 of the present invention, title key information and the like are recorded and updated on a nonvolatile RAM (for example, a ferroelectric memory). FIG. 4 shows a performance comparison between the flash memory and the ferroelectric memory. In FIG. 4, both types of memory are non-volatile and are guaranteed for approximately 10 years. The data rewrite unit can be rewritten in units of 1 byte, for example, in the ferroelectric memory, while the flash memory can be in a sector unit (for example, 512 B). The write cycle is 1 / 10th of 100 ns, and the guaranteed number of write times is 10 billion times as large as 100,000 times.

  Therefore, when the nonvolatile RAM 105 is a ferroelectric memory, even if the update frequency of the title key information etc. is 100 times, 100 ns × 32 bytes × 100 times = 320 μs, and the time overhead in updating the title key information etc. is It is only 320 μs, and the title key information and the like can be updated and recorded at a higher speed than in the past (when the title key information and the like are recorded once per recording).

  That is, if the semiconductor memory device of the present invention is used, it is possible to achieve both enhanced content protection and high-speed access. Furthermore, since the guaranteed number of rewrites is 10 billion, there is no problem in the life of the nonvolatile RAM 105, that is, there is no problem in the life of the SD memory card.

  Other non-volatile RAMs, such as magnetic recording type occasional write / read memory (MRAM), ovonic unified memory (OUM), or resistance RAM (RRAM), also have substantially the same performance as ferroelectric memory (FeRAM). Therefore, these nonvolatile memories may be used as the nonvolatile memory 105 for the protection area. In particular, the performance required for these nonvolatile memories is that the rewriting speed in a relatively small data unit of 1 bit to several tens of bytes is higher than that of the flash memory.

  In addition, since the flash memory 113 and the nonvolatile RAM 105 are provided as the main memory, the content protection information updated and recorded at the time of mutual authentication is stored on the nonvolatile RAM 105 side, and the rest is stored in the flash memory 113. The non-volatile RAM 105 needs a relatively small capacity. Therefore, when the controller unit 112 is integrated as an LSI (control LSI), it is easy to incorporate the nonvolatile RAM 105 in the control LSI. By incorporating the nonvolatile RAM 105 in the controller unit (control LSI) 112, the nonvolatile RAM 105 cannot be directly observed. Further, the nonvolatile RAM 105 and other logic circuits (for example, the address management information 108) in the controller unit (control LSI) 112 are mixedly wired, or the nonvolatile RAM 105 is distributed inside the controller unit (control LSI) 112. Accordingly, it is difficult to specify the recorded contents of the nonvolatile RAM 105 when observing from the LSI surface, and it is possible to enhance the content protection in these aspects.

  A semiconductor memory device according to the present invention has a content protection function in a semiconductor memory device having a content protection (copyright protection) function, particularly in a semiconductor memory device that updates and records content protection information during mutual authentication for content protection. Both enhancement and high-speed access can be achieved, and in the future, it will be useful as a small recording medium for various digital devices that perform content recording / playback that requires copyright protection in particular.

The block diagram which showed the structure of the semiconductor memory device by embodiment of this invention Schematic showing the mechanism of copyright protection in electronic music distribution related to the semiconductor memory device Conceptual diagram showing a configuration of a title key according to the semiconductor memory device Explanatory diagram showing performance comparison between flash memory and ferroelectric memory

Explanation of symbols

100 Host device 101 Host I / F unit 102 CPU
103 RAM
104 ROM
105 Nonvolatile RAM
106 Title Key Management Information 107 Title Key 108 Address Management Information Control Unit 109 Nonvolatile Memory Control Unit 110 Volatile RAM
111 Address management information 112 Controller 113 Flash memory 114 Key revocation information 115 Media ID
116 Media unique key 117 Encrypted content 118 Unencrypted content 119 Semiconductor memory device

Claims (7)

A nonvolatile memory that records at least content data; a nonvolatile RAM that stores content protection information that is updated and recorded at least during mutual authentication; and a nonvolatile memory control unit that controls access to the nonvolatile memory and the nonvolatile RAM. With
The semiconductor memory device according to claim 1, wherein the nonvolatile RAM has a higher rewrite speed at least in units of small data than the nonvolatile memory. 2. The semiconductor memory device according to claim 1, wherein the non-volatile RAM, the non-volatile memory control unit, and one semiconductor integrated circuit are configured. 3. The semiconductor memory device according to claim 2, wherein the nonvolatile RAMs are arranged in a distributed manner on the semiconductor integrated circuit. 4. The semiconductor memory device according to claim 1, wherein the nonvolatile RAM is a ferroelectric memory (FeRAM). 4. The semiconductor memory device according to claim 1, wherein the non-volatile RAM is a magnetic recording type arbitrary write / read memory (MRAM). 4. The semiconductor memory device according to claim 1, wherein the non-volatile RAM is an ovonic unified memory (OUM). 4. The semiconductor memory device according to claim 1, wherein the nonvolatile RAM is a resistance RAM (RRAM).

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