JP4501349B2 - System module execution device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a system module execution device that reads and executes a system module, which is software such as an OS and an application, from an external storage unit, and transmits and receives data by connecting to a network. In place Related.
[0002]
[Prior art]
As digital devices such as personal computers are connected to the Internet, attacks such as destruction by malicious persons called crackers and intrusions of computer viruses are increasing. As one of the measures for constructing a safe system that can withstand such an attack, it is considered to use only a trusted digital authentication method for software operating in the device and start only the authenticated reliable software.
[0003]
However, conventional software systems (Operating System: OS) such as Windows (registered trademark) of Microsoft Corporation and Linux (Linux) do not take measures against such software reliability. . Even if such an authentication function is added later, there is no clear basis for whether the entire system including the kernel, which is the core of the OS, can be trusted. Questions arise.
[0004]
Under such circumstances, for example, Japanese Patent Application Laid-Open No. 2002-152196 discloses the following program authentication method for authenticating and executing software. First, it is confirmed by the built-in function unit of the portable device that the hash value is generated by the program main body and the private key that is paired with the public key that represents the origin of the program. Next, when the parent device authenticates the portable device by the public key method using the public key and the secret key, and the authentication is successful, the program has a genuine origin based on the hash value confirmation by the portable device. Determine if it is a thing. As described above, it is assumed that when the parent device succeeds in authenticating the portable device and the program has a genuine source, the program is authenticated with the public key. Then, the authenticated software is executed.
[0005]
Japanese Patent Laid-Open No. 10-333902 discloses the following computer system with a falsification detection function. After initializing the basic input / output system (BIOS) with the boot program stored in the ROM of the control unit, the OS stores the first saved information stored in the auxiliary storage device. The file to be inspected is read without going through the OS according to the read contents. Using these read contents and the second saved information stored in the ROM, the presence or absence of falsification of the inspected file is inspected. After confirming that there is no tampering, the OS loader is called to start the OS. For this reason, it is a technique that brings about an effect that the presence or absence of alteration of the OS loader, the OS file, or any other file can be surely verified before the OS loader or OS is started.
[0006]
[Patent Document 1]
JP 2002-152196 A
[Patent Document 2]
JP-A-10-333902
[0007]
[Problems to be solved by the invention]
By the way, the techniques disclosed in Patent Document 1 and Patent Document 2 read data such as hash values and algorithms from the outside to the control unit and execute them in the control unit. In the case of an attack, it is difficult to determine whether the authentication process is correct.
Further, no measures have been taken when updating a system module such as an OS.
[0008]
The present invention has been made in view of the above circumstances, stores data and algorithms necessary for realizing processing independent of the OS in a secure state, and performs software authentication processing in a secure state in the control unit. System module execution device that can execute correctly Set For the purpose of provision.
[0009]
In addition, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a system module update method for an electronic device that can update a system module in a secure state.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, a system module execution device according to the present invention includes a system module acquisition unit that acquires a system module, an electronic signature acquisition unit that acquires an electronic signature attached to the system module, Right holder public key certificate storage unit for storing the public key certificate for the right holder attached with the public key, and a public key certificate verification unit for the right holder for verifying whether the public key certificate for the right holder is defective. An electronic signature verification unit that verifies the electronic signature attached to the system module based on the public key of the right holder, and a system that executes the system module according to a verification result of the electronic signature verification unit Module execution part When update of the system module is requested, a right to update the system module is calculated using a unique secret key and a hash function defined for the update module to be updated, and the update module A system module update unit that performs an update by checking only a system module that has a right to update by checking whether the hash value before update and the hash value after update included in Is provided.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment is connected to a network such as the Internet, and transmits / receives video, audio, text data, control data, and the like to / from other electronic devices connected to the network and a server of an information provider. Network-connected electronic equipment. For example, a video camera that transmits video data over the Internet, a digital still camera, and a network-connected video playback device, video recording / playback device, or audio data service server that downloads video data from a video data service server over the Internet A network-connected audio playback device, an audio recording / playback device, and the like that download audio data.
[0019]
Hereinafter, it is referred to as a network-connected electronic device, but is not limited to the above-described devices and devices. If a network connection is possible, a so-called consumer electronic device (consumer) such as a mobile phone, a personal digital assistant, or a monitor device is used. electronics: CE) Of course, business electronic devices connected to the network are also targeted. Compared to the case where a computer executes a plurality of software manufactured by a plurality of arbitrary software developers under an OS, the network-connected electronic device is limited in use and is licensed by the device manufacturer or the device manufacturer. Run software manufactured by a known software developer from the source.
[0020]
First, a first embodiment of the network connection type electronic apparatus 1 will be described. In the first embodiment, as shown in FIG. 1, a control processor 2 is connected to a ROM 4, a RAM 5, an input / output interface (I / O I / F) 6, and a network I / O via an internal bus 3. A configuration connected to F7 is adopted.
[0021]
In order to safely start the entire system, the control processor 2 executes all the system modules operating in the system, for example, software such as an OS and an application after verifying the integrity. In order to perform such authentication, the basis (starting and starting point) of authentication is required.
[0022]
As shown in FIG. 2, if A is reliable (trusted), the integrity of B can be proved by → A. If the integrity of B can be proved, the integrity of B1 can be proved by → B. Also, A can be trusted, so the completeness of C can be proved by → A. Thus, if A can be trusted, A can be used as a basis for authentication, and an authentication chain such as B, B1, B2,..., C, C1, C2,.
[0023]
Therefore, the control processor 2 uses a secure device to secure the basis for the authentication. Specifically, the control processor 2 securely activates and executes the network-connected electronic device 1 to execute and execute a cryptographic operation circuit (described later), a ROM in which an IPL (Intial Program Loader) is written, a secret key unique to the control processor, and a hash value. Table memory is integrated. In other words, a number of devices that would otherwise be connected to the outside via an internal bus are made into one chip.
[0024]
The ROM 4 is an auxiliary storage unit connected to the control processor 2 via the internal bus 3. Similarly, the RAM 5 is used as an auxiliary storage device and work area connected via the internal bus 3. The I / O I / F 6 is an interface for an input operation unit such as a key operation unit and a jog dial. It is also an interface for an output unit such as a video output unit or an audio output unit. The network I / F 7 is an interface for connecting to a network such as the Internet.
[0025]
As shown in FIG. 3, the control processor 2 includes a cryptographic operation circuit 11, a ROM (hereinafter referred to as IPL ROM) 12 in which IPL is written, a secret key 13 unique to the control processor, and a hash value table memory 14 Are integrated into one chip.
[0026]
The cryptographic operation circuit 11 includes cryptographic operations and authentication operations necessary for the network-connected electronic device 1, for example, hash functions such as SHA1, MD5, and MASH, hash functions such as HMAC-SHA1, and computations related to signatures such as ECC. Calculation of common key cryptography such as AES, DES, Triple-DES, and public key cryptography such as RSA.
[0027]
The cryptographic operation is an operation that prevents a third party from understanding a message transmitted over a network. Furthermore, the cryptographic operation is also used when information is stored in a RAM or a secondary storage device.
[0028]
The authentication calculation is an operation related to authentication processing, and is divided into counterpart authentication, user authentication, message authentication, and digital authentication depending on the authentication target. In particular, digital authentication is a technique for guaranteeing the validity of a document, and is performed by a calculation using a public key.
[0029]
The hash function is a mathematical processing method used for digital authentication and integrity check. Disturb long data and compress it into a hash value of a certain length (eg 128 bits, 160 bits, etc.). It is a safe hash function condition that it is difficult to estimate the input from the hash value and that the probability that the hash values of two different data match is extremely small.
[0030]
As an operation related to the signature, elliptical cryptography (Elliptic Curve Cryptosystem: ECC), which is a kind of public key cryptography, is used. The key size is smaller than the conventional RSA cipher. In general, 160-bit ECC can achieve almost the same strength as RSA encryption having a data length of 1024 bits. Of course, the RSA encryption may be used, or another signature algorithm may be used.
[0031]
Common key cryptography is a cipher in which the key to be encrypted is the same as the key to be decrypted, and both the sender and the receiver have secretly. Also called private key cryptography. In the calculation of the common key encryption, the secret key is shared between the sender and the receiver in advance to perform the encryption calculation. AES (Advanced Encryption Standard) is a procedural public key encryption. The block length is selected from 128 bits and the key length is selected from 128/192/256 bits. DES (Data Encryption Standard) is also a procedure public key cipher. Data is encrypted into a 64-bit data block unit of 56 bits key + 8 bits parity part. Triple-DES is a method in which the keys are lengthened by arranging three stages of DES to increase security.
[0032]
In public key cryptography, the key to be encrypted is different from the key to be decrypted, one of the keys is made public, and the other key is secret, and is also called asymmetric cryptography. When public key cryptography is used confidentially, the sender encrypts it using the recipient's public key and sends the ciphertext. The recipient decrypts it using a secret key known only to him and obtains the original plaintext. RSA (Rivest-Shamir-Adleman Scheme) bases safety on the difficulty of factoring large integers n.
[0033]
The cryptographic operation circuit 11 does not necessarily require all of the operations for encryption, authentication, hash function, signature, common key encryption, open key encryption, etc. In addition, cryptographic processing related to authentication processing is performed.
[0034]
The IPL written in the IPL ROM 12 is a minimum process necessary for the network-connected electronic device 1 to read a system module that is software or an object such as an OS or an application, such as a memory test. Further, processing related to system module reading and integrity confirmation, which will be described later, is also included in the IPL, and the processing related to this integrity confirmation is important.
[0035]
The secret key 13 unique to the control processor will be described as K. The secret key (K) 13 is a key unique to the control processor, and is used to decrypt the common key cipher. Of course, it is also used for encryption. In the second embodiment to be described later, it is also used for checking the hash value table. If the system module is encrypted with the secret key K, it is used for decryption.
[0036]
In the first embodiment, the hash value table memory 14 records a hash value table in advance. FIG. 4 shows a system module that is read from the ROM 4 or RAM 5 of FIG. 1 when the network-connected electronic device 1 is activated, and a table relating to the hash value. The system module 21 is loaded from the ROM 4 or RAM 5, the algorithm 22, and the hash value 23. The hash value 23 is obtained when the algorithm 22 is applied to the system module 21. That is, if the hash value is calculated by applying an algorithm called SHA1 calculation to the module A, it means “83f9c9aee9893b9defba9883187f38bc8f9aa824”.
[0037]
Here, for the sake of convenience, the module 21 to be loaded, the algorithm 22 and the hash value 23 are used, but the format is actually understood by the electronic device.
[0038]
The hash value table in FIG. 4 also shows the order in which the system modules are read. Here, the electronic device reads the system modules in the order of A, B, C, and D.
[0039]
As described above, this hash value table is written in the hash value table memory 14 in the processor in advance. As described above, since the hash value for collation of the system module exists in the hash value table memory 14 inside the processor, the hash table cannot be tampered with or deleted, and the hash value for collation can be trusted. .
[0040]
The hash value table may not be written in the hash value table memory in advance, but may be written in the hash value table memory inside the processor during the startup flow of the electronic device. Details of this case will be described later.
[0041]
FIG. 5 shows a processing procedure when the electronic apparatus is activated when the hash value table is written in the hash value table memory in advance. Describe each location where the hash value table exists.
[0042]
When the power of the electronic device is turned on, the IPL in the IPL ROM 12 of the control processor 2 is executed (step S1). Next, with reference to the hash value table written in the hash value table memory 14, the system module is read from an external memory, for example, the RAM 5 (step S2). Next, the integrity of the read system module is checked (step S3).
[0043]
The integrity check is performed by applying the algorithm 22 of FIG. 4 to the system module and collating it with the hash value 23 (step S3). If the hash values do not match (NG), the main cause is that the system module has a problem (such as tampering), and an error is determined and the process ends. At this time, the electronic device is not activated. Alternatively, if the electronic device has a function of outputting an error code or the like, an error and an error code may be output (step S4). If the hash values match in step S3 (OK), it is checked whether all the system modules have been read (step S5). If they have been read (YES), the electronic device has been activated (step S6). If not read (NO), the process returns to step S2 to read the next system module.
[0044]
As described above, the first embodiment of the network-connected electronic device 1 includes the cryptographic operation circuit 11, the IPL ROM 12, the secret key 13 unique to the control processor, and the hash value table memory 14 as shown in FIG. One chip. In particular, since the hash value table is written in the hash value table memory 14 in advance, the hash table cannot be tampered with or deleted, and can be trusted as a hash value for verification. For this reason, according to the first embodiment, it is possible to trust that the network-connected electronic device 1 immediately after startup is operated by a reliable software group that has not been maliciously altered. Also, as a basis for authenticating that the application or the like used after that has not been altered by the user or the administrator, such as falsification or replacement. This system can be used.
[0045]
Next, a second embodiment of the network connection type electronic apparatus 1 will be described. Also in the second embodiment, as shown in FIG. 1, the control processor 2 is connected to the ROM 4, RAM 5, input / output interface (I / O I / F) 6, and network I / F 7 via the internal bus 3. This is the configuration. However, the hash value table is not written in advance in the hash value table memory 14 of FIG. 3, but is written in the hash value table memory inside the processor during the startup flow of the electronic device. It is assumed that the hash value table is encrypted by the processor-specific secret key K13 or the key K ′ generated based on K and stored in the external memory 4 or 5.
[0046]
The processing procedure of the second embodiment will be described with reference to FIG. First, when the power of the electronic device is turned on, the IPL in the IPL ROM 12 of the control processor is executed (step S11). Next, the hash value table is read from the external memory (step S12). Next, the read hash value table is checked (step S13).
[0047]
The check of the hash value table in step S13 is performed by decrypting the hash value table with the processor-specific secret key K13 or another key K ′ generated from K. Check whether the information obtained by decryption is in the hash value table format.
[0048]
If the hash value table format is not correct as a result of the check in step S13, the main cause is that the hash value table has a defect (such as falsification), so the electronic device does not start or an error is output to the device. If there is a function to do so, an error is output (step S14). As a result of the check in step S13, if the format of the hash value table is correct (OK), the hash value table is expanded in the hash value table memory 14 (step S15).
[0049]
Next, referring to the hash value table, the system module is read from the external memory (step S16). Then, the integrity of the read system module is checked (step S17). For the integrity check, an algorithm 22 is applied to the system module 21 of FIG.
[0050]
If the hash value does not match in the module check in step S17, the main cause is that the system module has a defect (such as tampering), and the electronic device does not start or an error is output to the electronic device. If there is an error, an error is output (step S18).
[0051]
If the hash values match in the system module check in step S17, it is checked whether all the system modules have been read (step S19). If they have been read, the electronic device is activated and finished (step S19). If not, the process returns to step S16 to read the next system module from the external memory.
[0052]
In the processing procedure shown in FIG. 6, the system module is not encrypted, but may be encrypted with the processor-specific secret key K or another key K ′ generated from K. Decoding may be performed before the integrity check in step S17 in step 6 and after reading out the system module in step S16.
[0053]
As described above, the second embodiment of the network-connected electronic device 1 includes the cryptographic operation circuit 11, the IPL ROM 12, the secret key 13 unique to the control processor, and the hash value table memory 14 as shown in FIG. One chip. In particular, the hash value table memory 14 is written with the hash value table from the external memory during the startup flow of the electronic device, and is stored in the hash value table memory 14 integrated with the control processor 2 during operation. Therefore, the hash table cannot be tampered with or deleted, and the hash value for verification can be trusted. For this reason, according to the second embodiment, it is possible to trust that the network-connected electronic device 1 immediately after startup is operated by a reliable software group that has not been maliciously altered. Also, as a basis for authenticating that the application or the like used after that has not been altered by the user or the administrator, such as falsification or replacement. This system can be used.
[0054]
Next, a third embodiment of the network connection type electronic apparatus 1 will be described. In the third embodiment, as shown in FIG. 1, the control processor is connected to the ROM 4, RAM 5, input / output interface (I / O I / F) 6, and network I / F 7 via the internal bus 3. It is the composition which is. However, instead of the control processor 2, a control processor 30 shown in FIG. 7 is used.
[0055]
In FIG. 7, the control processor 30 securely starts and executes the network-connected electronic device 1 to execute a cryptographic operation circuit 31, a ROM 32 in which an IPL (Initial Program Loader) is written, a secret key 33 unique to the control processor, a CA. (Certificate Authority) public key certificate 34 and right holder's public key certificate 35. In particular, it is characteristic that two types of public key certificates are stored in the control processor 30. These public key certificates are listed in the system module list of FIG. 8 described later, and publicly attached to the system module by the right holder of the module (one of the module creator, module distributor, electronic device manufacturer, etc.). Used to verify a public key infrastructure (PKI) based electronic signature. It is characterized in that the integrity of the system module is maintained by verifying the electronic signature.
[0056]
The cryptographic operation circuit 31 includes cryptographic operations and authentication operations necessary for the network-connected electronic device 1, for example, hash functions such as SHA1 and MD5, and hash functions such as HMAC-SHA1. , Computation related to signatures such as ECC, computation of common key computations such as AES and Triple-DES, computation of public key cryptography such as RSA, and the like. All of these operations are not essential, but at least cryptographic operation processing mainly related to authentication processing is performed.
[0057]
The IPL written in the IPL ROM 32 is a minimum process necessary for the network-connected electronic device 1 to read a system module that is software, for example, a memory test. Further, processing related to system module reading and authentication, which will be described later, is also included in the IPL, and the processing related to authentication is important.
[0058]
The secret key 33 unique to the control processor will be described as K like the secret key 13. The secret key (K) 33 is a key unique to the control processor, and is used to decrypt the encryption. Of course, it is also used for encryption.
[0059]
The CA public key certificate 34 is a digital certificate issued by a certificate authority (CA). A CA public key is attached. Used to ensure document correctness.
[0060]
The right holder public key certificate 35 is a digital certificate that certifies the public key of the module right holder (one of the module creator, the module distributor, and the electronic device manufacturer). A rights holder's public key is attached.
[0061]
FIG. 8 shows a list of system modules to be read by the electronic device and the reading order. The IPL stored in the IPL ROM 32 performs a process of reading the system modules before reading them from the external memory. For convenience, a system module to be loaded is used, but in actuality, the device is in a format that can be understood by the device. Also, the system module list of FIG. 8 is added with a PKI-based electronic signature by the right holder of the module (any one of the module creator, the module distributor, the electronic device manufacturer, etc.), as in the system module. In the third embodiment, the integrity of the system module can be maintained by verifying the PKI-based electronic signature using the control processor 30 as described above.
[0062]
FIG. 9 shows a processing procedure when the third embodiment is activated. When the power source of the electronic device is turned on, the IPL in the IPL ROM 32 of the processor is executed (step S21). Next, the CA public key certificate 34 is read (step S22) and checked (step S23). Since it is recorded in the processor, the check in step S23 can be omitted.
[0063]
If the CA public key certificate 34 is not correct in the check in step S23, the CA public key certificate 34 is the main cause, and the electronic device does not start or has an error output function to the electronic device. Output an error.
[0064]
Next, the right holder's public key certificate 35 is read (step S24) and checked (step S25). Since it is recorded in the control processor 30, the check in step S25 can be omitted.
[0065]
If the check in step S25 is not correct, the main cause is a failure of the right holder's public key certificate 35, and if the electronic device does not start or if the electronic device has an error output function, an error is output.
[0066]
Next, the module list of FIG. 8 in the external memory is read (step S26). Then, the signature of the read module list is checked (step S27). The signature is checked here using the public key of the right holder attached to the right holder public key certificate.
[0067]
If the result of the check in step S27 is incorrect, the main cause is a malfunction (such as falsification) in the module list, and if the electronic device does not start or if the electronic device has an error output function, an error is output.
[0068]
Next, referring to the module list, the system module is read from the external memory (step S28). Next, the signature of the read system module is checked (step S29). This check is the same as the check in step S27.
[0069]
If the check in step S29 is not correct, the main cause is a malfunction (tampering) of the system module, and if the electronic device does not start or if the electronic device has an error output function, an error is output.
[0070]
Next, it is checked whether or not all the system modules have been read (step S30). If they have been read, the electronic device is activated (step S31). If not read, the process returns to step S28 to read the next system module.
[0071]
In the process of FIG. 9, the system module is not encrypted, but may be encrypted with the processor-specific secret key K or another key K ′ generated from K. In this case, the signature check Decoding may be performed before
[0072]
As described above, the third embodiment of the network-connected electronic device 1 stores the CA public key certificate 34 and the right holder's public key certificate 35 in the control processor 30, as shown in FIG. A public key infrastructure (PKI) -based electronic signature attached to the module list and the system module by the right holder of the module (one of the module creator, module distributor, electronic device manufacturer, etc.) Since it is used for verification, the integrity of the system module can be maintained. For this reason, according to the third embodiment, it is possible to trust that the network-connected electronic device 1 immediately after startup is operated by a software group that is not subject to malicious tampering. Also, as a basis for authenticating that the application or the like used after that has not been altered by the user or the administrator, such as falsification or replacement. This system can be used.
[0073]
Next, a fourth embodiment of the network connection type electronic apparatus 1 will be described. In the fourth embodiment, as shown in FIG. 1, the control processor 2 is connected to the ROM 4, RAM 5, input / output interface (I / O I / F) 6, and network I / F 7 via the internal bus 3. This is the configuration. As in the second embodiment, the hash value table memory 14 integrated with the control processor 2 shown in FIG. 3 does not have a hash value table written in advance, and the electronic device is activated. During the flow, data is read from an external memory (for example, ROM 4 or RAM 5) and written. The control processor 2 having such a configuration performs a process of updating the system module created by the right holder of the system module.
[0074]
FIG. 10 shows an update module created by the right holder of the system module. The module 51 includes an algorithm 52, a hash value 53 before update, a hash value 54 after update, and a new system module 55.
[0075]
The update module only needs to be configured by information for limiting which system module is updated and the new system module, and is not necessarily configured as shown in FIG.
[0076]
The right holder of the system module calculates the hash value H of the previous update module using the processor-specific secret key K13. For example, if the update module is M,
H = HMAC-SHA1 (K, M)
The operation is performed. This is an operation in which the key K is added to the hash function SHA1. The processor-specific secret key K used here is shared in advance between the right holder of the system module and the electronic device (strictly, the processor). Therefore, by using the hash value by HMAC-SHA1, the electronic device can check whether or not the right holder of the system module, strictly speaking, the update module has the right to update the system module.
[0077]
The right holder of the system module gives the update module M and the hash value H to the electronic device via, for example, the memory 4 or 5.
[0078]
FIG. 11 shows a processing procedure when the system module is updated in the fourth embodiment. First, the control processor 2 reads the update module M, the processor-specific secret key K, and the hash value H (step S41). Next, the hash value H ′ is calculated,
H ′ = HMAC-SHA1 (K, M)
Whether the hash value H received from the right holder of the system module matches is checked (step S42). That is,
H '= H
Check whether is true. By this inspection, the electronic device determines whether the right holder of the system module is the correct partner. This is because it is clear from the examination that the right holder of the system module shares the processor-specific secret key K with the electronic device. If they do not match, an error process, for example, a message such as “Update failed” is output and the process stops. Also, an error code may be output to stop.
[0079]
When the calculated hash value H ′ matches the received hash value H in the inspection in step S42 (OK), the module 51 is taken out from the update module M shown in FIG. 10 (step S43), and the hash It is confirmed whether the module exists in the value table (FIG. 4) (step S44). If it does not exist, error processing is performed.
[0080]
If the module corresponding to the module 51 exists in the hash value table of FIG. 4 as a result of the confirmation in step S44, the pre-update hash value 53 is extracted from the update module M (step S45), and the hash value table (FIG. 4) It is confirmed whether or not it matches the corresponding hash value (step S46). If they do not match, error processing is performed.
[0081]
If they match in step S46 (OK), the updated hash value 54 is extracted from the update module M (step S47). Next, the new system module 55 is extracted from the update module M (step S48), and a hash value is calculated (step S49). This hash value calculation uses the algorithm 52 of the update module M. It is confirmed whether the result of the calculation in step S49 matches the updated hash value extracted in step S47 (step S50). If they do not match, error processing is performed.
[0082]
If they match in step S50, the system module is updated (step S51), and the hash value table is updated (step S52).
[0083]
For example, a case where the update module M created by the right holder of the system module is related to the module C in the table shown in FIG. 4 will be described below. In FIG. 11, the module 51 is “C”, and the algorithm 52 is “SHA1”.
[0084]
First, in step S41 of FIG. 11, the control processor 2 reads the update module M, the processor-specific secret key K, and the hash value H. This hash value H is obtained by the right holder of the system using the processor-specific secret key K13.
H = HMAC-SHA1 (K, M)
Is calculated as follows. In FIG. 4, “9aa8b7b3c... Dba”.
[0085]
In step S42, the control processor 2 uses the processor-specific secret key 13 and the update module M,
H ′ = HMAC-SHA1 (K, M)
The hash value H ′ is calculated as follows, and it is checked whether or not it matches the hash value H received from the right holder of the system module. If the hash value H ′ calculated by the control processor 2 is also “9aa8b7b3c... Dba”, the control processor 2 takes out the module 51 from the update module M shown in FIG. It is confirmed whether or not the module exists in the hash value table (FIG. 4) (step S44).
[0086]
In step S44, a module corresponding to the module 51 exists as C in the hash value table of FIG. Therefore, in step S45, the pre-update hash value 53 is extracted from the update module M, and it is confirmed whether or not it matches the corresponding hash value in the hash value table (FIG. 4) (step S46). Here, it is assumed that “9aa8b7b3c... Dba” matches.
[0087]
In step S47, the updated hash value 54 is extracted from the update module M. For example, assume that the updated hash value is “f9b18d348... 2349a”. Next, C is extracted from the update module M as the new system module 55 (step S48), and a hash value is calculated using the algorithm 52 of the update module M (step S49). Assume that the hash value calculated here is “f9b18d348... 2349a”.
[0088]
In step S50, the result of the calculation in step S49 and the updated hash value extracted in step S47 are confirmed in step S50, the system module C is updated (step S51), and the hash value table is updated (step S52). As a result, the updated hash value table of the system module C is obtained as shown in FIG.
[0089]
As described above, the fourth embodiment of the network-connected electronic device 1 includes the cryptographic operation circuit 11, the IPL ROM 12, the secret key 13 unique to the control processor, and the hash value table memory 14 as shown in FIG. One chip. The hash value table memory 14 is written with the hash value table from the external memory during the startup flow of the electronic device, and is stored in the hash value table memory 14 integrated with the control processor 2 during operation. become. In the fourth embodiment, when the process of updating the system module created by the right holder of the system module is performed, the right to update the system module is checked, and only the system module having the right to update is accurately determined. And update can be performed. Since it is possible to update while maintaining a secure state, even if the system is started after updating the system module, the system is operated by a group of reliable software that has not received malicious tampering. Can be trusted. Also, as a basis for authenticating that the application or the like used after that has not been altered by the user or the administrator, such as falsification or replacement. This system can be used.
[0090]
Next, a fifth embodiment of the network connection type electronic apparatus 1 will be described. In the fifth embodiment, as shown in FIG. 1, the control processor is connected to the ROM 4, RAM 5, input / output interface (I / O I / F) 6, and network I / F 7 via the internal bus 3. It is the composition which is. However, as in the third embodiment, a control processor 30 shown in FIG. 7 is used instead of the control processor 2. The control processor 30 performs processing for updating the system module created by the right holder of the system module.
[0091]
FIG. 13 shows an update module created by the right holder of the system module. A module 71 and a new system module 72 are included.
[0092]
The right holder of the system module has its own private key S _M Is used to calculate the signature D of the previous update module. For example, if the update module is M,
D = DSA (S _M , M)
The operation is performed. Secret key S _M Is a secret key corresponding to the public key of the right holder public key certificate 35 included in the control processor 30. The right holder of the system module gives the update module M and the signature D to the electronic device 1.
[0093]
FIG. 14 is a diagram showing a processing procedure when the system module is updated in the fifth embodiment. Since the system module is updated after the electronic device 1 is activated, the CA public key certificate and the rights holder public key certificate are inspected at the time of activation. Therefore, although the same processing is omitted here, the same inspection may be performed without omission. In that case, the processing from step S21 to step S25 in FIG. 9 is performed before step S61.
[0094]
In FIG. 14, first, the update module M, signature D, and right holder public key are read (step S61). Next, the signature D is verified (step S62). The signature verification uses a verification algorithm corresponding to the signature generation algorithm. If the signature is not correct, an error process, for example, a message such as “Update failed” is output and stopped, or an error code is output and stopped.
[0095]
In step S62, the update module is checked. If the signature is correct, the module 71 is extracted from the update module M (step S63), and it is confirmed whether the module exists in the system module list shown in FIG. 8 (step S64). ). If it does not exist, error processing is performed.
[0096]
If it is determined in step S64 that the module exists, the new system module is extracted from the update module M (step S65), and the signature of the new system module is verified (step S66). If the signature is not correct, error handling is performed. If it is determined in step S66 that the signature is correct, the system module is updated (step S67).
[0097]
As described above, the fifth embodiment of the network-connected electronic device 1 stores the CA public key certificate 34 and the right holder's public key certificate 35 in the control processor 30, as shown in FIG. A public key infrastructure (PKI) -based electronic signature attached to the module list and the system module by the right holder of the module (one of the module creator, module distributor, electronic device manufacturer, etc.) Used to verify. In the fifth embodiment, when the process of updating the system module created by the right holder of the system module is performed, the right to update the object is checked, only the object having the right is accurately determined, and the update is performed. Can be executed. Since it is possible to update while maintaining a secure state, even if the system is started after updating the system module, the system is operated by a group of reliable software that has not received malicious tampering. Can be trusted. Also, as a basis for authenticating that the application or the like used after that has not been altered by the user or the administrator, such as falsification or replacement. This system can be used.
[0098]
Furthermore, with the system as in the fifth embodiment, it is possible to allow a plurality of right holders of system modules to exist. When there are a plurality of right holders of system modules, the public key certificates may be recorded in the control processor 30 by the number of right holders of the system modules.
[0099]
By the way, in the first embodiment, the second embodiment, and the fourth embodiment of the network-connected electronic device 1, in the configuration shown in FIG. 3, the hash value table is stored in the hash value table memory 14 in advance or during device activation. Was written. Using this hash value table, when the electronic device 1 is started up, the integrity of the system module to be used is checked to ensure that it is started up with the correct module in a secure state. The electronic device 1 is activated. In order to check the integrity of the system module, hash values of all modules used in the electronic device 1 are required. However, it may be difficult to record the hash values of all modules in the limited memory resource of the hash value table memory 14.
[0100]
Therefore, when managing the hash value of the system module in the electronic device having the limited hash table memory 14, even if the system module is increased by considering a plurality of system modules as one system module, the hash is increased. The value table can be managed in a limited memory.
[0101]
Hereinafter, a case where the system module is not compressed will be described. FIG. 15 shows a module ID 81 that uniquely defines a system module and a module name 82. It shows that the names of the system modules whose module ID 81 is “1, 2, 3, 4, 5, 6, 7” are “A, C, G, D, B, F, E”. Although the system module name 82 is explicitly shown here, it may be an item that can be identified in the object to be used, for example, an address where the system module is recorded.
[0102]
FIG. 16 shows a hash value for each module. Each hash value includes an ID 91, a system module 92, an algorithm 93 for deriving the hash value, and a hash value 94. Here, although the algorithm name is shown as the algorithm 93, it may be an identifier that can be identified within the usage target, for example, an instruction for calling the algorithm. In FIG. 16, for example, when the hash value ID is 5, the hash value is derived by the algorithm “SHA1” for the system module ID of FIG. 15, that is, the system module name is B, and the result is It means "8d34fba01b88da3f9eac0394bd4bca84da94abda" in hexadecimal.
[0103]
The case where two modules S and P are added in the state of FIGS. 15 and 16 will be described with reference to FIG. A system module having a system module ID 81 of 8 and a system module name 82 of S and a system module having a system module ID 81 of 9 and a system module name 82 of P are newly added. FIG. 18 shows a hash value for each module in FIG. Simply, the bottom two lines with ID91 of 8 and 9 are increasing.
[0104]
FIG. 19 shows a compressed version of the information shown in FIG. In FIG. 19, the hash value 104 is calculated by integrating the system module ID 102 with 4 and 5, and 7 and 8 in FIG. Due to the integration, FIG. 19 and FIG. 16 appear to be the same size. Here, the reason is that it is not considered that the integrated information is added to the system module ID 102 in FIG.
[0105]
Which part is integrated may be either a plurality of continuous system module IDs or a plurality of non-consecutive system module IDs, or any number.
[0106]
In the integration method, a hash value is calculated by regarding a plurality of system modules as one system module. That is, usually, the portion where the hash value = hash function (one system module) is
Hash value = hash function (module | module | ・ ・ | module)
Calculate the hash value as The symbol “|” means connection.
[0107]
FIG. 20 is a flowchart of a process for updating the hash value table. When the system module is added (step S71), the system module table is updated (step S72). This is an addition to FIG. 15 to FIG. Next, it is confirmed whether or not the memory reaches the limit by adding the system module (step S73). This depends on the number of added system modules n and the amount of memory consumed per system module y.
ny
As the current memory usage m and the memory limit value M,
M> m + ny (1)
Calculate whether or not If the expression (1) holds, the hash value of the added system module is calculated (step S75). This corresponds to FIG. If equation (1) does not hold, the system module IDs are integrated (step S74). This corresponds to the portion (102) in FIG. Thereafter, a hash value is calculated (step S75). This corresponds to FIG.
[0108]
Next, a case where a plurality of system modules are compressed and regarded as one will be described. FIG. 21 is obtained by adding a system module P and a system module S to FIG. 15 in the same manner as the example shown in FIG. When the system module ID 111 in FIG. 21 is 4, it means that the system module D and the system module B are integrated. Similarly, when the system module ID is 6, it means that the system module E and the system module S are integrated. FIG. 22 shows the hash value of each module at this time. Since the system module ID and the ID 121 for each hash value have a one-to-one correspondence, the system module ID is not required in FIG. As a result, the information to be retained is less than the above example by the system module ID of FIG.
[0109]
Which part is integrated may be a plurality of continuous system module IDs or a plurality of discontinuous system module IDs. In the example of FIG. 22, system module IDs 4, 5, 7, and 8 in FIG. 17 are integrated.
[0110]
As a method of integrating a plurality of system modules, there are a method of simply integrating system modules and a method of integrating system modules while compressing them.
[0111]
FIG. 23 is a flowchart of a process for updating the hash value table. When the system module is added (step S81), the system module table is updated (step S82). This is an addition to FIG. 15 to FIG. Next, it is confirmed whether or not the memory reaches the limit due to the addition of the system module (step S83). This uses the same calculation formula (1) as in the above example. If the expression (1) holds, the hash value of the added system module is calculated (step S85). This corresponds to FIG. If equation (1) does not hold, the system modules are integrated (step S84). This corresponds to the portion (112) in FIG. Thereafter, a hash value is calculated (step S85). This corresponds to FIG.
[0112]
Hereinafter, the effect of using the memory efficiency will be described. As described above, when managing the hash value of a system module, not only can the memory be used efficiently by combining a plurality of system modules as a single system module, but also a certain system can be integrated. It becomes difficult to perform tampering attacks on modules. This is because, in practice, falsification cannot be made without obtaining information on which system modules are integrated.
[0113]
Note that in the implementation of the hash value table, all system modules that are subject to hash calculation are classified according to the number of stages in the table, but this division method must be designed in consideration of calculation speed and efficiency. Don't be. As a consideration,
(A) The total size of the system modules included in the hash value calculation at each stage of the hash table is set to the same level at each stage.
(B) Each system module included in the same hash value calculation is positioned logically or physically close so that the total file access time is efficient.
(C) The number of system modules included in the hash value calculation is made substantially the same at each stage of the hash table.
However, what condition should be given priority may be determined according to the capability, application, structure, etc. of the device.
[0114]
【The invention's effect】
According to the present invention, data and algorithms necessary for realizing processing independent of the OS can be stored in a secure state, and software authentication processing can be correctly executed in the secure state in the control unit. In addition, the system module can be updated in a secure state.
[Brief description of the drawings]
FIG. 1 is a block diagram of a first embodiment of a network-connected electronic device.
FIG. 2 is a diagram for explaining an authentication chain;
FIG. 3 is a diagram illustrating a configuration of a control processor;
FIG. 4 is a diagram illustrating a hash table.
FIG. 5 is a flowchart showing a processing procedure at the start-up of the first embodiment of the network-connected electronic device.
FIG. 6 is a flowchart showing a processing procedure when starting up the second embodiment of the network-connected electronic device.
FIG. 7 is a diagram showing a control processor constituting a third embodiment of the network connection type electronic apparatus.
FIG. 8 is a diagram showing a list of system modules.
FIG. 9 is a flowchart showing a processing procedure when starting up the third embodiment of the network-connected electronic device.
FIG. 10 is a diagram showing an update module updated by a fourth embodiment of the network-connected electronic device.
FIG. 11 is a flowchart showing a processing procedure when starting up the fourth embodiment of the network-connected electronic device.
FIG. 12 is a diagram showing a hash value table after the system module is updated.
FIG. 13 is a diagram showing an update module created by a right holder of a system module.
FIG. 14 is a flowchart showing a processing procedure at the start-up of the fifth embodiment of the network-connected electronic device.
FIG. 15 is a diagram illustrating a module ID that uniquely defines a system module and a system module name.
FIG. 16 is a diagram showing a hash value for each system module.
FIG. 17 is a diagram illustrating a system module ID and a system module name when two system modules S and P are added.
18 is a diagram showing a hash value for each module in FIG. 17;
FIG. 19 is a diagram showing a hash value obtained by compressing the information shown in FIG. 18;
FIG. 20 is a flowchart illustrating a processing procedure for updating a hash value table.
FIG. 21 is a diagram showing a system module ID and a system module name when a system module P and a system module S are added to FIG. 15;
FIG. 22 is a diagram showing a hash value table that is reduced by the system module ID.
FIG. 23 is a flowchart showing a processing procedure for updating a hash value table;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Network connection type electronic device, 2 Control processor, 11 Cryptographic operation circuit, 12 IPL ROM, 13 Secret key, 14 Hash value table memory, 30 Control processor, 31 Cryptographic operation circuit, 32 IPL ROM, 33 Secret key, 34 CA public key certificate, 35 rights holder public key certificate

Claims (1)

A system module acquisition unit for acquiring a system module;
An electronic signature acquisition unit for acquiring an electronic signature attached to the system module;
A rights holder public key certificate storage unit for storing a rights holder public key certificate to which the rights holder's public key is attached;
A rights holder public key certificate verifying unit that verifies whether the rights holder public key certificate has a defect;
An electronic signature verification unit that verifies the electronic signature attached to the system module based on the public key of the right holder;
A system module execution unit that executes the system module according to a verification result of the electronic signature verification unit;
When an update of the system module is requested, a right to update the system module is calculated using a unique secret key and a hash function defined for the update module to be updated, and the update module A system module execution device comprising: a system module update unit that checks whether a pre-update hash value and an after-update hash value are included, determines only a system module that has the right to update, and executes an update.

Images