JP2007013835A - Encoded data decoding device and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide secure encoded data decoding technique which will not expose a key information to the outside, and which is capable of coping with data of various encryption systems and formats. <P>SOLUTION: The encoded data decoding device is mounted by a programmable gate array capable of setting a circuit by an encoded circuit description information inputted from outside and its encoded data decoding device is constituted so as to be provided with a decoding circuit of an encoded circuit description information employing an encoding key for decoding a circuit description information, a circuit set by the decoded circuit description information to produce an encryption key, a circuit for decoding an encoded data encryption key inputted from outside employing the produced encryption key, and a circuit for decoding the encoded data inputted from outside employing the decoded data encryption key set by the decoded circuit description information. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an encrypted data decryption apparatus and method for decrypting encrypted data such as video content, and in particular, can decrypt data without exposing key information to the outside, and The present invention relates to an encrypted data decryption apparatus and method for realizing a secure encrypted data decryption technique capable of supporting data of various encryption methods and formats.

  In order to protect content in digital content distribution, a method of encrypting and distributing data is used.

  In this encrypted content distribution, it is necessary to distribute the data encryption key for decrypting the content to the distribution destination. As one of the methods, the data encryption key can be decrypted only by the private key held by the distribution destination. There is a way to encrypt and distribute in a certain form.

  In the encrypted data decryption apparatus used in such a distribution method, the secret key and the data encryption key are safely stored without being known to the outside, and the decryption process of the data encryption key and the decryption process of the data are externally performed. It is necessary to execute it securely without exposing the encryption key. In addition, depending on the application, it is required to cope with the change of the encryption method accompanying the upgrade and the reproduction of content of various types of formats. Also, tamper resistance is required to destroy the encryption key when an attack from the outside is detected.

  The encrypted data decryption apparatus as described above is usually realized by a dedicated LSI having resistance to external physical and electrical attacks.

  For example, a security chip used in smart cards, personal computers, etc. has a built-in dedicated memory for storing encryption keys and an encryption processing device, and encrypted data without exposing the encryption keys and plaintext data to the outside. Decryption processing of (encrypted data) is possible. Non-Patent Document 1 shown below describes the TPM standard, which is a type of security chip used in personal computers.

  However, a normal security chip for exchanging authentication information used in smart cards and personal computers does not have a function to decrypt encrypted broadband data such as video signals in real time. Decryption of the encrypted content, which is the object of the present invention, must be performed by a circuit outside the security chip, and the data encryption key is exposed outside the security chip. For this reason, the data decryption process cannot be performed in a state where the data encryption key is safely stored.

  On the other hand, a dedicated LSI for decrypting encrypted broadband data such as video content has been developed and used in fields such as DVD and digital television broadcasting. Non-Patent Document 2 shown below describes an example of an encryption / decryption LSI based on CPRM, which is standardized as a DVD encryption method.

  This dedicated LSI is designed so that the content can be decrypted without exposing the encryption key to the outside, but only the content of a specific encryption method and data format can be decrypted. In addition, since it is expensive to develop a dedicated LSI, it cannot be used when the device is not mass-produced.

  Recent advances in semiconductor technology have made it possible to implement encryption and decryption processing of wideband data such as video signals by using an FPGA (Field Programmable Gate Array). By using the FPGA for mounting the encrypted data decryption device, it becomes possible to decrypt data of various encryption methods and formats.

  One of the problems when using an FPGA as an encrypted data decryption device is that by extracting the circuit setting information of the FPGA, the operation of the encryption circuit performed inside the FPGA is analyzed, and the danger of the encryption key information being extracted It is to have sex.

However, in recent FPGAs, for the purpose of protecting assets of circuit design information, configuration data describing circuit setting information is encrypted and stored, and when the FPGA is started up, it is configured by a decryption circuit mounted inside the chip. Some of them have a function of decoding and loading the operation data. Non-Patent Document 3 shown below is an application note showing an example of a support related to encryption of configuration data in an FPGA.
"Trusted Platform Module (TPM) based Security on Notebook PCs-White Paper" Sundeep Bajikar, Mobile Platforms Group, Intel Corporation, June 20, 2002. (http://developer.intel.com/design/mobile/platform/downloads/ (Trusted_Platform_Module_White_Paper.pdf) Satoshi Yamaguchi, Narutaka Yoshida, Toshio Suzuki, Tsutomu Sasaki, Tetsuya Kawahara, Hideto Endo "Development of DVD Cryptographic LSI", Pioneer Technical Information Magazine 2003 Vol.12 No.3. (Http // www.pioneer.co.jp / crd1 / rd / pdf / 12-3-2.pdf) "Using High Security Features in Virtex-II Series FPGAs" Xilinx application note XAPP766 (http://www.xilinx.com/bvdocs/appnotes/xapp766.pdf)

  Against the background of such conventional technology, the present invention aims to realize the following technology.

  First, the realization of securely storing the data encryption key for decrypting the encrypted data and the encryption key for decrypting the encrypted data encryption key so as not to be known outside With the goal.

  An object of the present invention is to securely decrypt an encrypted data encryption key using the encryption key, and to further securely decrypt encrypted data using the decrypted data encryption key. To do.

  And it aims at realization of enabling it to change an encryption key with a parameter given from the outside.

  And it aims at realization of enabling it to perform a decoding process with respect to the content of various encryption systems and data formats.

  Then, when the device is subjected to a physical attack, an object is to make the device inoperable and make it impossible to extract the encryption key.

  In order to achieve these objects, the present invention is to implement an encrypted data decryption device with a programmable gate array capable of performing circuit setting by means of encrypted circuit description information input from the outside, The encrypted data decryption apparatus includes (1) a circuit description information decryption circuit that decrypts the encrypted circuit description information using a decryption encryption key for the circuit description information, and (2) decryption of the circuit description information decryption circuit. An encryption key generation circuit configured to generate an encryption key set by the circuit description information, and (3) an encryption key generated by the encryption key generation circuit set by the circuit description information decrypted by the circuit description information decryption circuit. A data encryption key decryption circuit for decrypting an encrypted data encryption key input from the outside, and (4) circuit description information decrypted by the circuit description information decryption circuit. Using the decoded data encryption key data encryption key decrypting circuit is configured to include a data decoding circuit for decoding the encrypted data input from the outside.

  When this configuration is adopted, it is preferable that the decryption encryption key of the circuit description information is held in the memory and discarded when a physical attack is detected.

  In the encrypted data decryption apparatus of the present invention configured as described above, for example, at the time of setup, a decryption encryption key for circuit description information is input from the outside. For example, when the apparatus is activated, the encrypted circuit description information is input from the outside, and the circuit description information is decrypted using the decryption encryption key of the circuit description information.

  Subsequently, according to the decrypted circuit description information, an encryption key generation circuit for generating an encryption key, a data encryption key decryption circuit for decrypting an encrypted data encryption key input from the outside, and an encryption input from the outside A data decoding circuit for decoding data is set.

  Subsequently, the encryption key generation circuit generates and sets the encryption key by performing a logical operation on the encryption key generation parameter input from the outside and the encryption key set by the decrypted circuit description information. The encrypted data encryption key input from the outside is decrypted by the generated data encryption key decryption circuit using the generated encryption key.

  The preparation for the decryption process of the encrypted data input from the outside is completed by the above process. When the encrypted data is input from the outside, the decrypted data encryption key is set by the set data decryption circuit. The encrypted data is decrypted and output.

  As described above, the encrypted data decryption apparatus according to the present invention performs circuit setting (circuit generation) based on encrypted circuit description information input from the outside in order to support contents of various encryption methods and data formats. Implemented by a programmable gate array (eg, FPGA).

  Further, the encrypted data decryption device according to the present invention encrypts the encryption key generation circuit in order to securely store the encryption key for decrypting the encrypted data encryption key in a form that is not known from the outside. The programmable gate array is set according to the described circuit description information.

  Further, the encrypted data decryption device according to the present invention provides an encryption key for decrypting an encrypted data encryption key and a data encryption key for decrypting the encrypted data without exposing the data to the outside. In order to perform this decryption process, the data encryption key decryption circuit and the data decryption circuit are set in the programmable gate array by the encrypted circuit description information.

  In addition, the encrypted data decryption apparatus according to the present invention provides an encryption key generation parameter and circuit description input from the outside in an encryption key generation circuit in order to realize a function of changing an encryption key according to an externally applied parameter. A final encryption key is generated by a logical operation with the encryption key generated as part of the information.

  In addition, the encrypted data decryption device according to the present invention uses a physical encryption key for decryption of circuit description information in order to make the device inoperable and make it impossible to extract the encryption key when subjected to a physical attack. Stored in a programmable gate array internal memory that is backed up by a backup power supply that is shut off when a specific attack is detected, thereby erasing the decryption encryption key for circuit description information when a physical attack is performed This makes it impossible to extract the encryption key.

  According to the present invention, the encryption key generation circuit, the data encryption key decryption circuit, and the data decryption circuit are set in the programmable gate array by the encrypted circuit description information. It is possible to prevent the information of the existing encryption method from being taken out from the outside.

  Further, according to the present invention, it is possible to decrypt the data encryption key and decrypt the data without exposing the encryption key and the data encryption key to the outside.

  Further, according to the present invention, since the encryption key generation circuit can generate an encryption key based on parameters given from the outside, the contents of the encryption key can be changed without changing the circuit description information. can do. From this point, it is possible to perform control so that a correct encryption key cannot be generated unless a correct parameter is given.

  Further, according to the present invention, the decryption encryption key for the circuit description information used for decrypting the encrypted circuit description information is held by the backup power supply that is cut off when a physical attack is detected. Therefore, when a physical attack is detected, the backup power supply is cut off, making it impossible to extract information from the encryption key generation circuit, the data encryption key decryption circuit, and the data decryption circuit. it can.

  In addition, according to the present invention, since all circuits necessary for data decryption are mounted inside a programmable gate array, by changing the circuit description information, contents of various encryption methods and data formats can be obtained. Decoding processing can be performed.

  Hereinafter, the present invention will be described in detail according to embodiments.

  FIG. 1 illustrates an embodiment of the encrypted data decryption apparatus 10 of the present invention.

  The encrypted data decryption apparatus 10 of the present invention is implemented by an FPGA (Field Programmable Gate Array), and as shown in this figure, a conf encryption key 12 held in a volatile memory 11, Configuration data decryption circuit 13 for decrypting encrypted configuration data (FPGA internal circuit setting information), encryption key generation circuit 14 set by configuration data, and data encryption set by configuration data A key decryption circuit 15 and a data decryption circuit 16 set by configuration data are provided.

  The configuration data decryption circuit 13 is prepared in advance regardless of the configuration data. The configuration data decryption circuit 13 reads the encrypted configuration data 20 from the outside and uses the encryption key 12 for the configuration to read the encrypted data. Configuration data is input by decoding the configuration data 20.

  The encryption key generation circuit 14 is set (generated) by the configuration data decrypted by the configuration data decryption circuit 13, and is an encrypted data encryption key (data encryption key: for decrypting encrypted video data). An encryption key for decrypting the key is generated.

  The data encryption key decryption circuit 15 is set (generated) by the configuration data decrypted by the configuration data decryption circuit 13, and is encrypted using the encryption key generated by the encryption key generation circuit 14 from the outside. Decrypt the data encryption key.

  Here, when the encryption key generation circuit 14 generates a secret key for RSA public key encryption as an encryption key, the data encryption key decryption circuit 15 uses a data encryption key encrypted with the public key for RSA public key encryption. By decrypting using the secret key, the data encryption key is decrypted.

  The data decryption circuit 16 is set (generated) by the configuration data decrypted by the configuration data decryption circuit 13 and is encrypted using the data encryption key decrypted by the data encryption key decryption circuit 15. Decode the video data.

  The encrypted data decryption apparatus 10 of the present invention configured as described above is implemented by an FPGA and is configured so that an internal circuit for performing decryption of encrypted data by configuration data can be changed. Thus, it becomes possible to perform decryption processing on contents of various encryption methods and data formats.

  In realizing this configuration, the encrypted data decryption apparatus 10 according to the present invention takes into account that the configuration of the internal circuit is exposed when the configuration data is stolen. A configuration is adopted in which the encrypted configuration data 20) is input and decrypted.

  Thus, since the encrypted configuration data is used, the encryption key generated by the encryption key generation circuit 14 cannot be known from the outside, and high security can be ensured.

  Furthermore, in the encrypted data decryption apparatus 10 of the present invention, it is considered that when the conf encryption key 12 is stolen, the configuration data can be stolen by decrypting the encrypted configuration data 20. Then, the conf encryption key 12 is held in the volatile memory 11 backed up by the backup power supply 30 provided outside, and from the backup power supply 30 to the volatile memory 11 when the occurrence of a physical attack is detected. By providing a backup power shutoff circuit 40 that shuts off the power supply, the configuration encryption key 12 is discarded when a physical attack occurs.

  In this way, the security key 12 for conf is discarded when a physical attack occurs, so high security can be ensured.

  As described above, the encryption key generation circuit 14 is set (generated) by the configuration data decrypted by the configuration data decryption circuit 13 and generates an encryption key for decrypting the encrypted data encryption key. In order to generate this encryption key, a final encryption key is generated by a logical operation of the encryption key generation parameter input from the outside and the encryption key generated as part of the configuration data. It is also possible to adopt a configuration of doing.

  By adopting this configuration, the encryption key can be changed by changing the encryption key generation parameter, so that the encryption key can be changed without changing the configuration data. In addition, by providing a password, device serial number, etc. as an encryption key generation parameter from the outside, it is possible to realize a restriction that a correct encryption key cannot be generated unless the correct password and serial number are given to the FPGA. You will also be able to.

  2 to 5 show the processing executed by the encrypted data decryption apparatus 10 of the present invention in the form of flowcharts.

  Next, processes executed by the encrypted data decryption apparatus 10 according to the present invention will be described in order according to these flowcharts.

  At the time of setup, the encrypted data decryption apparatus 10 of the present invention reads the conf key encryption key 12 composed of a common key encryption key and the like and is backed up by the backup power source 30 as shown in the flowchart of FIG. A process of writing in the existing volatile memory 11 is performed.

  In this way, according to the process at the time of setup, the conf encryption key 12 is held in the volatile memory 11 backed up by the backup power source 30, as shown in FIG.

  On the other hand, the encrypted data decryption apparatus 10 according to the present invention, when the apparatus power is turned on, first, in step 20, the configuration data decryption circuit 13 prepared in advance is applied to the configuration data decryption circuit 13 as shown in the flowchart of FIG. To read the encrypted configuration data given from the outside.

  That is, as shown in FIG. 7, the configuration data decryption circuit 13 reads the encrypted configuration data 20.

  Subsequently, in step 21, the configuration data decryption circuit 13 decrypts the read encrypted configuration data 20 by using the encryption key 12 for the conflict stored in the volatile memory 11 to obtain the configuration data. obtain.

  Subsequently, in step 22, the encryption key generation circuit 14, the data encryption key decryption circuit 15 and the data decryption circuit 16 are set according to the decrypted configuration data, and the process is terminated.

  In this way, according to the processing at the time of startup, as shown in FIG. 8, the encryption key generation circuit 14, the data encryption key decryption circuit 15, and the data decryption circuit 16 are set inside the FPGA. The encrypted data decryption apparatus 10 of the invention is constructed.

  On the other hand, when the encrypted data decrypting apparatus 10 of the present invention starts the decrypting process of the encrypted video data following the start-up process, first, as shown in the flowchart of FIG. When data is input after waiting for data to be input from the outside, the process proceeds to step 31 to determine whether or not an encryption key generation parameter has been input.

  When it is determined that the encryption key generation parameter has been input in accordance with this determination process, the process proceeds to step 32, where the encryption key generation circuit 14 sends one of the input encryption key generation parameter and configuration data. After the final encryption key is generated by a logical operation with the encryption key generated as a part, the process returns to step 30 to wait for the next input data.

  At this time, if an encryption key has already been generated, the encryption key is discarded, and the encryption key generated according to the newly input encryption key generation parameter is set as a new encryption key. To do.

  On the other hand, when it is determined that the encryption key generation parameter has not been input in accordance with the determination processing in step 31, the process proceeds to step 33 to determine whether or not an encrypted data encryption key has been input. to decide.

  When it is determined that an encrypted data encryption key has been input in accordance with this determination process, the process proceeds to step 34 where the data encryption key decryption circuit 15 uses the encryption key generated according to the process of step 32. After decrypting the input encrypted data encryption key, the process returns to step 30 to wait for the next input data.

  On the other hand, when it is determined that the encrypted data encryption key has not been input in accordance with the determination process in step 33, the process proceeds to step 35 to determine whether or not the encrypted video data has been input. Judging.

  When it is determined that the encrypted video data has been input in accordance with this determination process, the process proceeds to step 36 where the data decryption circuit 16 uses the data encryption key generated according to the process of step 34 to input it. After decrypting and outputting the encrypted video data, the process returns to step 30 to wait for the next input data.

  On the other hand, when it is determined that the encrypted video data has not been input in accordance with the determination process in step 35, the process proceeds to step 37, the process is executed in accordance with the input data, and the next input is performed. Return to step 30 to wait for data.

  As described above, as shown in the flowcharts of FIGS. 2 to 4, when the encrypted data decryption apparatus 10 of the present invention enters the setup process, it inputs the conf encryption key 12 and is backed up by the backup power source 30. It is processed so as to write to the volatile memory 11.

  Then, the encrypted data decryption apparatus 10 of the present invention receives the encryption configuration data 20 when it receives a start-up instruction when the power is turned on, decrypts it using the encryption key 12 for the comp, and based on that After the encryption key generation circuit 14, the data encryption key decryption circuit 15 and the data decryption circuit 16 are set, the encryption key generation parameters are input, and the encryption key generation circuit 14 generates the encryption key. Then, the encrypted data encryption key is input, and the data encryption key decryption circuit 15 performs processing to decrypt the data encryption key.

  Since the preparation for the decryption processing of the video data encrypted by the above processing is completed, the encrypted data decryption device 10 of the present invention continues when the encrypted video data is inputted. In step 16, the video data is decrypted and output using the data encryption key.

  During such processing, or when the power is not turned on, a malicious user attempts to read the conf key 12 by destroying the encrypted data decryption device 10 of the present invention. There are things to do.

  When such a physical attack is performed, as shown in the flowchart of FIG. 5, the backup power shutoff circuit 40 shuts off the power supply of the backup power supply 30, and thus the encryption key 12 for the conf is destroyed. Thus, it is possible to prevent the conf encryption key 12 from being stolen.

  Next, the features of the present invention and the effects of the features will be summarized.

(I) Features of the present invention As features of the present invention,
(1) The first feature is that the encrypted data decryption device is realized by a field programmable gate array (FPGA).
(2) The second feature is that the configuration data is stored in an encrypted form, and is decrypted and loaded with the encryption key for conf stored in the FPGA when the device is activated. ,
(3) The third feature is that the encryption key generation circuit is described as a part of the encrypted configuration data.
(4) The fourth feature is that the encryption key generation circuit has a function of generating an encryption key from an encryption key generation parameter given from the outside.
(5) A fifth feature is that an encrypted data encryption key decryption circuit and an encrypted data decryption circuit are mounted inside the FPGA.
(6) The sixth feature is that when the encryption key for decryption for decrypting the configuration data is held in the FPGA by the backup power supply and an attack on the device is detected, it is discarded by shutting off the power supply Have the ability to
That's what it means.

(Ii) Effect of the present invention As an effect of the present invention,
(1) With the first feature, it is possible to flexibly cope with changes in the encryption method and content data format by changing the configuration data.
(2) Due to the second feature, the configuration data can be securely stored in an encrypted form.
(3) Due to the third feature, the encryption key is stored in an encrypted form as part of the configuration data, so it can be stored securely, and part of the configuration data can be rewritten. The encryption key can be changed with
(4) According to the fourth feature, since the encryption key can be generated by the encryption key generation parameter given from the outside, the encrypted data decryption device cannot be used unless the correct encryption key generation parameter is given from the outside. It is also possible to change the encryption key without changing the configuration data by changing the encryption key generation parameter given from the outside. Since the circuit is encrypted, it is possible to make it impossible to know the encryption key from the encryption key generation parameter given from the outside.
(5) According to the fifth feature, since the decryption circuit for the data encryption key and the decryption circuit for the data are built in the FPGA, the encrypted data encryption key is decrypted inside the FPGA using the encryption key. Data can be decrypted without exposing the key to the outside,
(6) According to the sixth feature, when the device is attacked from the outside, the encrypted data decrypting device is cut off by shutting off the backup power source holding the encryption key for decryption for decrypting the configuration data. It is possible to disable the operation of the device itself and prevent the encryption key from being extracted.
Can be realized.

  According to the present invention, it is possible to provide an encrypted data decryption apparatus capable of safely decrypting various encrypted data including broadband data.

It is an example of 1 embodiment of the encryption data decoding apparatus of this invention. The process which the encryption data decoding apparatus of this invention performs is shown with the form of a flowchart. The process which the encryption data decoding apparatus of this invention performs is shown with the form of a flowchart. The process which the encryption data decoding apparatus of this invention performs is shown with the form of a flowchart. The process which the encryption data decoding apparatus of this invention performs is shown with the form of a flowchart. It is explanatory drawing of the process which the encryption data decoding apparatus of this invention performs. It is explanatory drawing of the process which the encryption data decoding apparatus of this invention performs. It is explanatory drawing of the process which the encryption data decoding apparatus of this invention performs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Encrypted data decryption device 11 Volatile memory 12 Conf encryption key 13 Configuration data decryption circuit 14 Encryption key generation circuit 15 Data encryption key decryption circuit 16 Data decryption circuit 20 Encrypted configuration data 30 Backup power supply 40 Backup power supply cutoff circuit

Claims (8)

An encrypted data decryption device implemented by a programmable gate array capable of performing circuit setting by means of encrypted circuit description information input from the outside,
A circuit description information decryption circuit for decrypting the encrypted circuit description information using a decryption encryption key for the circuit description information;
An encryption key generation circuit that is set by the circuit description information decrypted by the circuit description information decryption circuit and generates an encryption key;
Data encryption key decryption set by the circuit description information decrypted by the circuit description information decryption circuit and decrypts an encrypted data encryption key input from the outside using the encryption key generated by the encryption key generation circuit Circuit,
A data decryption circuit configured to decrypt encrypted data input from the outside using the data encryption key decrypted by the data encryption key decryption circuit set by the circuit description information decrypted by the circuit description information decryption circuit That
A feature of an encrypted data decryption apparatus. The encrypted data decryption device according to claim 1,
The encryption key for decryption of the above circuit description information is input from the outside during setup,
And the circuit description information decryption circuit, when starting up the device, receives the decrypted circuit description information from the outside and decrypts it.
A feature of an encrypted data decryption apparatus. The encrypted data decryption device according to claim 1 or 2,
The encryption key generation circuit performs a logical operation between an encryption key generation parameter input from the outside and an encryption key set by the circuit description information decrypted by the circuit description information decryption circuit, thereby obtaining a final encryption Generating the key,
A feature of an encrypted data decryption apparatus. The encrypted data decryption device according to any one of claims 1 to 3,
The encryption key for decryption of the circuit description information is held in the memory and discarded when a physical attack is detected.
A feature of an encrypted data decryption apparatus. An encrypted data decryption method executed by an encrypted data decryption apparatus implemented by a programmable gate array capable of performing circuit setting by encrypted circuit description information input from the outside,
Decrypting the encrypted circuit description information using the decryption encryption key for the circuit description information,
According to the decrypted circuit description information, an encryption key generation circuit for generating an encryption key, a data encryption key decryption circuit for decrypting an encrypted data encryption key input from the outside, and encrypted data input from the outside Set the data decryption circuit to decrypt,
The encryption key generation circuit generates an encryption key, the data encryption key decryption circuit uses the generated encryption key to decrypt an encrypted data encryption key input from the outside, and the data In the decryption circuit, using the decrypted data encryption key, decrypting the encrypted data input from the outside,
A method for decrypting encrypted data. The encrypted data decryption method according to claim 5,
During setup, input the encryption key for decryption of the circuit description information from the outside,
When the device starts up, the encrypted circuit description information is inputted from the outside and decrypted.
A method for decrypting encrypted data. The encrypted data decryption method according to claim 5 or 6,
The final encryption key is generated by performing a logical operation on the encryption key generation parameter input from the outside and the encryption key set by the decrypted circuit description information in the encryption key generation circuit. The
A method for decrypting encrypted data. The encrypted data decryption method according to any one of claims 5 to 7,
The encryption key for decryption of the circuit description information is held in the memory and discarded when a physical attack is detected.
A method for decrypting encrypted data.

Images