JP2007213718A - Semiconductor integrated circuit and inspection method of semiconductor integrated circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor integrated circuit with built-in nonvolatile device, wherein a test is carried out while keeping a secrecy of data mounted in the nonvolatile device and a position of error can be specified when the error occurs. <P>SOLUTION: A check arithmetic circuit 25 performs an arithmetic operation corresponding to the arithmetic operation for generating secret CRC data with respect to the secret information data which are read out from the nonvolatile device 10. A comparison circuit 26 compares the secret CRC data read out from the nonvolatile device 10 with a result of arithmetic operation in the check arithmetic circuit 25. When this comparison results in non-coincidence and the error is detected, an encryption processing circuit 42 encrypts the secret information data and the secret CRC data by using a secret key stored in a secret key register 41 and outputs them outside the semiconductor integrated circuit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for testing a non-volatile device in a semiconductor integrated circuit incorporating the non-volatile device.

As a technology for testing a nonvolatile device that stores confidential information built in a semiconductor integrated circuit, a predetermined calculation such as CRC (Cyclic Redundancy Check) is performed on confidential information data mounted on a ROM, and the calculation result is obtained. In some cases, comparison is made with check redundant data, which is a result of a predetermined calculation performed on confidential information data in advance, and a comparison result of coincidence / mismatch is output to the outside (see Patent Document 1). This technique makes it possible to perform a test without outputting confidential information mounted in the ROM to the outside.
Japanese Patent Laid-Open No. 2001-344992 (page 5, first figure)

  However, in the conventional technology, even when an error is found, it cannot be determined whether the error is caused by confidential information data on the nonvolatile device or check redundant data. In addition, since it is impossible to detect which bit an error has occurred, it becomes difficult to analyze the cause of the error.

  In view of the above problems, the present invention is a semiconductor integrated circuit incorporating a nonvolatile device, enabling the testing of the nonvolatile device while maintaining the confidentiality of the confidential information stored in the nonvolatile device, and specifying the error occurrence position. The challenge is to make this possible.

  In order to solve the above-described problem, the solution provided by the invention of claim 1 is a semiconductor integrated circuit including a non-volatile device for storing confidential information data. The non-volatile device stores data stored outside the semiconductor integrated circuit. And redundant data storage means for storing redundant data for check obtained by performing a predetermined operation on the confidential information data, and redundant data for check stored in the redundant data storage means A test circuit for performing a test of the non-volatile device using the check circuit, wherein the test circuit performs a calculation corresponding to the predetermined calculation on confidential information data read from the non-volatile device A ratio between the circuit and the result of the check operation circuit and the redundant data for checking stored in the redundant data storage means A comparison circuit that performs encryption using a predetermined secret key for the confidential information data and the redundant data for checking, and the calculation result and the check as a comparison result of the comparison circuit When a mismatch with the redundant data for use is detected, the encryption result of the encryption processing circuit is output to the outside of the semiconductor integrated circuit.

  According to the first aspect of the invention, when a mismatch between the operation result of the check operation circuit and the check redundant data is detected, the encryption result of the encryption processing circuit, that is, the secret encrypted using the predetermined secret key. Information data and redundant data for checking are output outside the semiconductor integrated circuit. For this reason, the location of the error is specified by decrypting the encrypted confidential information data and the redundant data for checking using a predetermined secret key and comparing it with the legitimate data to be mounted on the nonvolatile device. It becomes possible to do. At this time, since the confidential information data and the check redundant data are encrypted and output, only the authorized tester who possesses the predetermined secret key can decrypt the original confidential information data and the check redundant data. An unauthorized user cannot obtain confidential information data and redundant data for checking. Therefore, confidentiality of confidential information data is maintained. Even if the confidential information data is uncovered by an unauthorized user, the confidential information data is data containing an error, and damage can be minimized. Therefore, it is possible to specify the error occurrence position while maintaining the confidentiality of the confidential information data.

  In the invention of claim 2, the redundant data storage means in the semiconductor integrated circuit of claim 1 is the nonvolatile device.

  Further, in the invention of claim 3, the check redundant data in the semiconductor integrated circuit of claim 2 is stored in an address different from that of the confidential information data in the nonvolatile device.

  Furthermore, in the invention of claim 4, the check redundant data in the semiconductor integrated circuit of claim 2 is stored in the same address as the confidential information data in the nonvolatile device.

  In the invention of claim 5, the encryption processing circuit in the semiconductor integrated circuit of claim 1 encrypts only the confidential information data using a predetermined secret key.

  According to the invention of claim 5, it is possible to confirm whether or not there is an error in the confidential information data by decrypting and inspecting the confidential information data output after being encrypted. If it is determined that there is no error in the confidential information data, the error exists in the check redundant data. At this time, since the check redundant data is not used except during the test, it can be seen that the found error has no problem in the function of the semiconductor integrated circuit.

  In a sixth aspect of the present invention, the test circuit in the semiconductor integrated circuit of the first aspect includes a secret key register for storing the predetermined secret key.

  In the invention of claim 7, the test circuit in the semiconductor integrated circuit of claim 6 has a predetermined circuit stored in the secret key register when the comparison circuit detects a match between the operation result and the check redundant data. It is assumed that the secret key is updated based on the check redundant data.

  According to the seventh aspect of the present invention, the secret key used for encryption of the confidential information data and the check redundant data differs depending on the position where the error occurs, so that the confidentiality of the output data can be increased.

  In the invention of claim 8, it is assumed that a predetermined initial value is given to the secret key register in the semiconductor integrated circuit of claim 7.

  According to the invention of claim 8, when an error is found at the start of the test, it is possible to specify the secret key used for encrypting the output data.

  According to another aspect of the present invention, the non-volatile device reads out stored data to the outside of the semiconductor integrated circuit as a method for inspecting a semiconductor integrated circuit including a non-volatile device for storing confidential information data. Preprocessing for storing the redundant data for check obtained by performing a predetermined calculation on the confidential information data in advance in the redundant data storage means of the semiconductor integrated circuit, and from the nonvolatile device A process for reading confidential information data, executing a calculation corresponding to the predetermined calculation on the read confidential data, reading check redundancy data from the redundant data storage means, and reading the result of the calculation process and the check redundancy A process of comparing data, and as a result of the comparison, the calculation result and the redundant data for checking When a match is detected, in which a processing for encrypting using a predetermined secret key with respect to the confidential data and the check redundant data.

  According to the present invention, when an error is detected as a result of the test of the nonvolatile device built in the semiconductor integrated circuit, the encryption result of the confidential information data and the redundant data for checking, or the encryption result of only the confidential information data Is output outside the semiconductor integrated circuit. Therefore, it is possible to specify the position where the error occurs without impairing the confidentiality of the confidential information data inside the nonvolatile device, and to analyze the cause of the error.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a semiconductor integrated circuit according to an embodiment of the present invention. In the semiconductor integrated circuit shown in FIG. 1, a ROM 10 as a non-volatile device is configured so that stored data that has been written cannot be read out of the semiconductor integrated circuit. Further, the semiconductor integrated circuit shown in FIG. 1 is configured such that the test of the ROM 10 can be realized without impairing the confidentiality of confidential information data such as microcode, secret key, and password. Further, when an error in the ROM 010 is detected as a result of the test, the confidential information data in which the error is found and the check redundant data corresponding to the confidential information data are encrypted and output using a predetermined secret key. It is configured as follows.

  In FIG. 1, (n + 1) pieces of confidential information data, that is, confidential information data (0) to (n) are mounted at lower addresses of the ROM 10. For each confidential information data (0) to (n), a redundant code by CRC (Cyclic Redundancy Check), that is, confidential CRC data (0) to (n) as redundant data for check is generated. These are mounted at the upper address of the ROM 10 as redundant data storage means.

  In the address space of the ROM 10, the confidential information data (0) to (n) are stored in order from the lowest address, and the confidential CRC data (0) to (n) are stored in order from the highest address. For example, the confidential CRC data (0) corresponding to the confidential information data (0) stored at the lowest address of the ROM 10 is stored at the highest address of the ROM 10. Such an address arrangement is suitable for the complementary check of the ROM 10.

  In FIG. 1, selectors 21 and 22, an address decoder (ADEC) 23, flip-flops (FF) 24 and 27, a check operation circuit (CRC) 25, a comparison circuit (COMP) 26, a secret key register 41, and an encryption processing circuit. 42, the OR circuit 43 and the inverter 44 constitute a test circuit. The logic circuit block (LOGIC) 30 is a circuit block used in the normal mode.

  The selectors 21 and 22 select and output the input of the input terminal A when the input S becomes “H” (high level). The address decoder 23 decodes an address signal input at the time of the test, and controls the check operation circuit 25, the comparison circuit 26, and the encryption processing circuit 42. The check calculation circuit 25 executes a calculation corresponding to a predetermined calculation at the time of generating the secret CRC data for the secret information data read from the ROM 10. The comparison circuit 26 compares the output of the check calculation circuit 25 with the confidential CRC data read from the ROM 10.

  The OR circuit 43 receives the output of the flip-flop 27 and the output of the flip-flop 24 as inputs, and applies these OR signals to the calc terminal of the encryption processing circuit 42. The secret key register 41 stores a predetermined secret key, and gives this secret key to the key terminal of the cryptographic processing circuit 42. The cryptographic processing circuit 42 encrypts the data input from the ROM 10 to the input terminal DIN using the secret key input to the key terminal at the rising edge of the signal input to the calc terminal. The encryption result is stored in the encryption processing circuit 42. Further, the encryption processing circuit 42 receives the signal obtained by inverting the output OUT of the comparison circuit 26 in the inverter 44 at the enable input en, and when the enable input en is asserted (“H”), the stored encryption result Is output from the output terminal DOUT. CLK is a clock signal for synchronization of each circuit block.

  During normal operation, the test signal TEST is “L” (low level), and the selectors 21 and 22 select the input of the input terminal B. That is, input data from the external terminals INA and INB is given to the ROM 10. These input data are supplied from another block in the semiconductor integrated circuit. The output DO of the ROM 10 is supplied to the logic circuit block 30.

  On the other hand, during the test, the test signal TEST becomes “H”, and the selectors 21 and 22 select the input of the input terminal A. That is, input data from the external terminals IN1 and IN2 is supplied to the address input ADD and read input READ of the ROM 10.

  The input data from the external terminal IN1 is also input to the address decoder 23. The address recorder 23 enables the output AOUT1 (“H”) when the input data from the external terminal IN1 indicates the address (address (0) to (n)) where the confidential information data is stored. When the output AOUT1 becomes “H”, the check arithmetic circuit 25 ahead of the output DO of the ROM 10 starts operation with a delay of one clock.

  At this time, when the output AOUT1 becomes “H”, the input to the terminal calc of the encryption processing circuit 42 becomes “H”, so that the encryption processing circuit 42 uses the secret key input to the terminal key to Cryptographic processing is performed on the input (in this case, confidential information data), and the result is held.

  When the input data from the external terminal IN1 indicates the address (address (n + 1) to (2n + 1)) where the confidential CRC data is stored, the address decoder 23 enables the output AOUT2 (“H )). When the output AOUT2 becomes “H”, the comparison circuit 26 compares the calculation result (IN1) of the check calculation circuit 25 with the confidential CRC data (IN2) read from the ROM 10. When the comparison results match, the output signal RESULT is asserted (“H”).

  At this time, since the input to the terminal calc of the cryptographic processing circuit 42 becomes “H” with a delay of one clock, the cryptographic processing circuit 42 uses the secret key input to the terminal key to input the terminal DIN (in this case). Performs encryption processing on confidential CRC data.

  When the comparison result by the comparison circuit 26 is inconsistent and the output signal RESULT is negated (“L”), the enable input en of the encryption processing circuit 42 is asserted (“H”). At this time, the encryption processing circuit 42 outputs the encryption result of the confidential information data and the encryption result of the confidential CRC data held from the output terminal DOUT. A signal output from the output terminal DOUT is output to the outside of the semiconductor integrated circuit via the external terminal EncOUT. On the other hand, when the comparison result by the comparison circuit 26 is coincident and the output signal RESULT is asserted (“H”), the enable input en of the encryption processing circuit 42 is negated (“L”). At this time, the encryption processing circuit 42 clears the encryption result of the confidential information data and the encryption result of the confidential CRC data that are held.

  FIG. 2 is a timing chart showing an operation during a test of the semiconductor integrated circuit shown in FIG.

  First, the test signal TEST is set to “H” in order to set the ROM 10 to the test mode. Next, a signal indicating the address address (0) where the confidential information data (0) is stored in the ROM 10 is input from the external terminal IN1, and the read input READ of the ROM 10 is enabled from the external terminal IN2. Enter "H". Then, the confidential information data (0) is read as the output DO of the ROM 10 at the next rise of the clock signal CLK.

  Further, the address decoder 23 outputs “H” as the output AOUT1 because the signal indicating the address address (0) is input. This signal “H” is latched for one clock by the flip-flop 24 and then supplied to the check operation circuit 25 as an enable input en. As a result, the check operation circuit 25 starts a CRC operation on the confidential information data (0) output from the ROM 10. The encryption processing circuit 42 encrypts the confidential information data (0) output from the ROM 10.

  One cycle before the check calculation circuit 25 completes the CRC calculation, the input data to the external terminal IN1 is changed to a value other than address (0) to (n), and the input data to the external terminal IN2 is negated ( “L”). Then, the output AOUT1 of the address decoder 23 is also negated, and the enable input en of the check operation circuit 25 is also negated with a delay of one cycle. Thereby, the calculation result of the check calculation circuit 25 is held at the output OUT.

  Next, a signal indicating the address address (2n + 1) where the confidential CRC data (0) corresponding to the confidential information data (0) is stored is input from the external terminal IN1, and the ROM 10 is read from the external terminal IN2. “H” is input so that the signal READ is enabled.

  Since the address decoder 23 receives the signal indicating the address address (2n + 1), it outputs “L” as the output AOUT1 and “H” as the output AOUT2. The comparison circuit 26 compares the output OUT of the check operation circuit 25 with the output DO of the ROM 10, that is, the confidential CRC data (0). As a result of the comparison, when the two match, the signal RESULT is asserted (“H”), and when they do not match, the signal RESULT is set to “L”. The cryptographic processing circuit 42 encrypts the confidential CRC data (0) output from the ROM 10. When the signal RESULT is negated (“L”) and the enable input en is asserted (“H”), the encryption processing circuit 42 stores the encryption result of the confidential information data and the encryption result of the confidential CRC data held therein. Is output from the output terminal DOUT. A signal output from the output terminal DOUT is output to the outside of the semiconductor integrated circuit via the external terminal EncOUT.

  Further, while the output AOUT2 is “H”, the signal COMPen is asserted for one cycle period and negated together with the output of the RESULT signal. The check operation circuit 25 is initialized by the falling edge of the signal COMPen.

  With the above operation, the test of the confidential information data (0) is completed.

  The same operation is performed while specifying the address address (1), address (2n), address address (2), address (2n-1), ..., address address (n), address (n + 1), The signal RESULT is monitored from the outside. From this result, it can be determined whether or not an abnormality has occurred in the ROM 10 due to a manufacturing problem or the like.

  When an error is detected by negating the signal RESULT, the external terminal EncOUT outputs the encryption result of the confidential information data and the confidential CRC data in which the error has occurred. At this time, the inspector who has the right decrypts the output encryption result using a predetermined secret key, and the obtained decryption result is correct to be implemented in the nonvolatile device. Can be compared with the data. This makes it possible to specify the position where the error has occurred.

  Even if an unauthorized user or an inspector who does not have the right obtains the encryption result of confidential information data and confidential CRC data output from the external terminal EncOUT, it does not have a secret key. Cannot be decrypted. Therefore, leakage of confidential information data can be prevented.

  In the configuration of FIG. 1, the secret key used in the cryptographic processing circuit 42 is a predetermined value stored in the secret key register 41. On the other hand, the secret key stored in the secret key register 41 may be updated. Thereby, the confidentiality of output data can further be improved.

  For example, in the configuration of FIG. 3, a selector 45 is added which takes the output DO of the ROM 10 and the stored value of the secret key register 41 as inputs and gives the output selected according to the output signal RESULT to the secret key register 41. When the output signal RESULT is asserted (“H”), that is, when the comparison circuit 26 detects a match between the operation result and the confidential CRC data, the selector 45 outputs the output DO of the ROM 10, that is, the confidential CRC data. Store in the register 41. As a result, the secret key stored in the secret key register 41 is updated. When the output signal RESULT is negated (“L”), the selector 45 selects the output of the secret key register 41, and therefore the value of the secret key register 41 is not updated. As a result, a fixed secret key is not used, and the secret key used for encryption of the confidential information data and the check redundant data differs depending on the position where the error occurs, so that the confidentiality can be improved.

  When the secret CRC data value is stored in the secret key register 41 and the bit length is different between the secret CRC data and the secret key, the bit length is set by performing an appropriate operation on the secret CRC data. It shall be aligned. The appropriate calculation may be a hash calculation such as SHA-1, or may be a method using a specified number of bits from the top of the confidential CRC data, or a method using a transposition table or the like.

  At this time, it is preferable to give a predetermined initial value to the secret key register 41. This makes it possible to specify the secret key used for encrypting the output data when an error is found at the start of the test.

  In this embodiment, the non-volatile device for storing confidential information is ROM, but other non-volatile devices such as Fuse may be used.

  The encryption performed by the encryption processing circuit 42 may use any method as long as it is a common key encryption such as DES, AES, Multi2, and Triple DES.

  In the present embodiment, when an error is detected, both the confidential information data and the confidential CRC data are encrypted and output. However, only the confidential information data may be encrypted and output. . For this purpose, for example, in the configuration of FIG. 1, the OR circuit 43 may be omitted so that only the output of the flip-flop 24 is given to the terminal calc of the encryption processing circuit 42. In this case, it is possible to confirm whether or not there is an error in the confidential information data. If there is no error, it can be confirmed that the detected error has no problem as a function of the semiconductor integrated circuit. .

  In the configuration of FIG. 1, the confidential CRC data is stored at an address different from that of the confidential information data. However, the confidential CRC data may be stored at the same address as the confidential information data. For example, as shown in FIG. 4, the corresponding confidential CRC data may be mapped to the upper bit position of the confidential information data.

  Further, here, the confidential CRC data is mounted on the ROM itself on which the confidential information data is mounted. However, the ROM incorporated in the semiconductor integrated circuit is different from the ROM on which the confidential information data is mounted. Confidential CRC data may be implemented in the storage means.

  Further, when changing the contents of the confidential information data, it is only necessary to change the confidential CRC data in accordance with the change. Therefore, it is not necessary to change the configuration of the test circuit, and therefore the development man-hours and the mask design cost can be greatly reduced.

  Further, data other than CRC redundant codes may be used for checking confidential information data. However, in this case, it is necessary to provide a check operation circuit in the test circuit for executing an operation corresponding to a predetermined operation for generating the check data.

  In the present embodiment, the synchronous ROM has been described as an example, but the same implementation can be easily realized even with an asynchronous ROM.

  In the present invention, it is possible to specify the position where an error has occurred without impairing the confidentiality of confidential information data inside the nonvolatile device. Therefore, in the inspection of the nonvolatile device built in the semiconductor integrated circuit, the cause of the error is analyzed. It is useful for performing efficiently.

1 is a block diagram showing a configuration of a semiconductor integrated circuit according to an embodiment of the present invention. 2 is a timing chart showing an operation during a test of the semiconductor integrated circuit shown in FIG. It is a block diagram which shows the structure of the semiconductor integrated circuit which concerns on the modification of one Embodiment of this invention. It is a figure which shows the other example of the data storage in ROM.

Explanation of symbols

10,10A ROM (nonvolatile device)
21 and 22 selector 23 address decoder 24 flip-flop 25 check operation circuit 26 comparison circuit 41 secret key register 42 encryption processing circuit 43 OR circuit 44 inverter 45 selector

Claims (9)

A semiconductor integrated circuit incorporating a non-volatile device for storing confidential information data,
The nonvolatile device is configured such that stored data cannot be read out of the semiconductor integrated circuit,
Redundant data storage means for storing redundant data for checking obtained by performing a predetermined operation on the confidential information data;
A test circuit for testing the nonvolatile device using redundant data for checking stored in the redundant data storage means;
The test circuit includes:
A check operation circuit that executes an operation corresponding to the predetermined operation on the confidential information data read from the nonvolatile device;
A comparison circuit that compares the operation result of the check operation circuit with the check redundant data stored in the redundant data storage means;
An encryption processing circuit that performs encryption using a predetermined secret key for the confidential information data and the redundant data for checking,
A semiconductor integrated circuit that outputs an encryption result of the encryption processing circuit to the outside of the semiconductor integrated circuit when a mismatch between the operation result and the check redundant data is detected as a comparison result of the comparison circuit circuit. The semiconductor integrated circuit according to claim 1,
2. The semiconductor integrated circuit according to claim 1, wherein the redundant data storage means is the nonvolatile device. The semiconductor integrated circuit according to claim 2.
The redundant data for checking is stored in an address different from that of the confidential information data in the nonvolatile device. The semiconductor integrated circuit according to claim 2.
The redundant data for checking is stored in the nonvolatile device at the same address as the confidential information data. The semiconductor integrated circuit according to claim 1,
2. The semiconductor integrated circuit according to claim 1, wherein the cryptographic processing circuit encrypts only the confidential information data using a predetermined secret key. The semiconductor integrated circuit according to claim 1,
The test circuit includes:
A semiconductor integrated circuit comprising a secret key register for storing the predetermined secret key. The semiconductor integrated circuit according to claim 6.
The test circuit includes:
Updating the predetermined secret key stored in the secret key register based on the check redundant data when the comparison circuit detects a match between the operation result and the check redundant data; A semiconductor integrated circuit. The semiconductor integrated circuit according to claim 7.
A semiconductor integrated circuit, wherein the secret key register is given a predetermined initial value. A method for inspecting a semiconductor integrated circuit containing a nonvolatile device for storing confidential information data,
The nonvolatile device is configured such that stored data cannot be read outside the semiconductor integrated circuit,
Pre-processing for storing redundant data for checking obtained by performing a predetermined operation on the confidential information data in advance in redundant data storage means of the semiconductor integrated circuit;
A process of reading confidential information data from the nonvolatile device, and executing an operation corresponding to the predetermined operation on the read confidential data;
Reading the check redundant data from the redundant data storage means, and comparing the result of the arithmetic processing with the read check redundant data;
As a result of the comparison, when a mismatch between the operation result and the check redundant data is detected, the confidential information data and the check redundant data are encrypted using a predetermined secret key. A method for inspecting a semiconductor integrated circuit, comprising:

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