JP7192658B2 - secure element - Google Patents

Description

The present invention relates to a secure element that is a one-chip microcomputer with tamper resistance.

The Secure Element is a one-chip microcomputer with tamper resistance. A secure element implements an application that is used in a particular system (for example, a payment system) and executes a series of sequences that require multiple cryptographic operations (encryption or decryption).

The secure element is equipped with a cryptographic coprocessor that performs cryptographic calculations instead of a CPU (Central Processing Unit) in order to speed up cryptographic calculations. For example, the semiconductor processing device (IC card) disclosed in Patent Document 1 has a cryptographic coprocessor that performs remainder calculations related to RSA and elliptic curve cryptography in place of the CPU.

In the case of a cryptographic operation that requires cryptographic parameters that define a mathematical formula, it is necessary to input the cryptographic parameters required for the cryptographic operation into the cryptographic operation coprocessor before performing the cryptographic operation using the cryptographic operation coprocessor. For example, in the elliptic product-sum calculation device disclosed in Patent Document 2, when performing the elliptic product-sum calculation, the cryptographic parameters P, Q, R, a, b, c, etc. required for the elliptic product-sum calculation are calculated by an arithmetic circuit. and let the arithmetic circuit calculate T=aP+bQ+cR.

If the data length of the cryptographic parameters required for a cryptographic operation is short, even if all the cryptographic parameters required for the cryptographic operation are input to the cryptographic operation coprocessor each time a cryptographic operation is performed, the time required for the sequence executed by the application will be short. not much different. However, if the data length of the cryptographic parameters required for the cryptographic computation is long, inputting all the cryptographic parameters required for the cryptographic computation into the cryptographic computation coprocessor every time the cryptographic computation The time to input to the arithmetic coprocessor is one factor that increases the time required for the sequences executed by the application.

The above problem will be explained with the elliptic curve cryptography defined in RFC5639. FIG. 4 is a diagram for explaining cryptographic parameters required for defining an elliptic curve in elliptic curve cryptography defined by RFC5639. The elliptic curve cryptography defined in RFC5639 requires 160 bits of cryptographic parameters, but FIG. 6 shows 512-bit cryptographic parameters.

The cryptographic parameters required for elliptic curve cryptography specified in RFC5639 are p (characteristic), A (coefficient of equation 1), B (coefficient of equation 1), x (value of x coordinate of base point), y (y-coordinate value of base point), q (prime order), h (cofactor) as cryptographic parameters.

As illustrated in FIG. 4, in the 512-bit elliptic curve cryptography specified by RFC5639, all six encryption parameters other than h are 512 bits. When performing multiple elliptic curve cryptographic operations without changing the cryptographic parameters, if the process of inputting six 512-bit cryptographic parameters to the cryptographic coprocessor is done only once, the sequences required by the application time can be shortened.

Japanese Patent Application Laid-Open No. 2008-310950 Japanese Patent Application Laid-Open No. 2004-233530

In view of this, the present invention provides a secure element equipped with a cryptographic coprocessor that performs processing related to cryptographic operations that require cryptographic parameters that define mathematical expressions. The purpose is to enable the process of inputting the cryptographic parameters to the cryptographic operation coprocessor only once.

The first invention to solve the above-mentioned problems is a cryptographic operation coprocessor that performs processing related to cryptographic operations that require cryptographic parameters that define mathematical expressions, and a cryptographic operation that uses the cryptographic operation coprocessor to perform the cryptographic operations. When the encryption parameter is input to the encryption operation coprocessor, the encryption operation unit stores the check code of the encryption parameter as a check code for identity confirmation in a memory, and stores the check code for the identity confirmation in a memory. When the cryptographic parameters are input to the cryptographic operation coprocessor in a state of being saved in the memory as a check code, the cryptographic parameters to be input to the cryptographic operation coprocessor before inputting the cryptographic parameters to the cryptographic operation coprocessor and the check code for identity confirmation stored in the memory at this time, and if the check codes match, the cryptographic parameter is not input to the cryptographic operation coprocessor. is a secure element characterized by

According to the secure element of the present invention, when the cryptographic parameter input to the cryptographic operation coprocessor and the cryptographic parameter input to the cryptographic operation coprocessor are the same, the cryptographic parameter can be prevented from being input to the cryptographic operation coprocessor. .

The figure explaining a secure element. A diagram explaining the architecture of a secure element. FIG. 4 is a diagram for explaining the operation of a cryptographic computation unit included in the secure element; FIG. 4 is a diagram for explaining cryptographic parameters required for Elliptic Curve cryptography;

Embodiments according to the present invention will now be described. This embodiment is intended to facilitate understanding of the present invention, and the present invention is not limited to this embodiment. In addition, unless otherwise specified, the drawings are schematic diagrams drawn to facilitate understanding of the present invention.

FIG. 1 is a diagram for explaining a secure element 1 according to this embodiment. The secure element 1 is a one-chip microcomputer with tamper resistance. As illustrated in FIG. 1, the secure element 1 is mounted on a medium or device such as a mobile terminal 1a, SIM 1b, IC card 1c, etc., for performing secure transactions (for example, payment transactions).

FIG. 2 is a diagram explaining the architecture of the secure element 1. As shown in FIG. The architecture of secure element 1 illustrated in FIG. 2 includes hardware 10 , operating system 11 and application 12 .

The hardware 10 of the secure element 1 becomes a one-chip microcomputer. The hardware 10 of the secure element 1 includes a CPU 101 (Central Processing Unit) as a central processing unit, a RAM 102 (Random Access Memory) as a main memory, and an NVM 103 (Non-volatile memory) as an electrically rewritable non-volatile memory. ), a timer 104 for measuring time, an I/O 105 for connecting to a host device, and a cryptographic calculation coprocessor 106 for performing predetermined cryptographic calculations instead of the CPU 101 are connected to an interface 107 . The cryptographic computations to be executed by the cryptographic computation coprocessor 106 are cryptographic computations that require cryptographic parameters that define mathematical expressions, and elliptic curve cryptography is well known as such cryptographic computations.

The operating system 11 of the secure element 1 is software that provides functions using the hardware 10 . The application 12 is software that executes a series of sequences requiring multiple cryptographic operations, and is software that runs on the operating system 11 .

An operating system 11 of the secure element 1 provides applications 12 with various functions that utilize the hardware 10 . As one of these functions, the secure element 1 has a cryptographic operation unit 110 that causes the cryptographic operation coprocessor 106 to perform cryptographic operations, and multiple types of APIs 111 (Application Programming Interfaces) for using the cryptographic operation unit 110. ing. The cryptographic calculation unit 110 is a function implemented by a computer program that operates the CPU 101 , and can be included in the library provided by the operating system 11 to the application 12 .

The detailed specifications of the API 111 for using the cryptographic computation unit 110 are arbitrary. Here, an API 111 for setting cryptographic parameters, an API 111 for setting cryptographic keys, an API 111 for setting calculation target data, and an API 111 for executing cryptographic calculations are included in the API 111 for using the cryptographic calculation unit 110 . The API 111 for setting cryptographic parameters is generally prepared for each type of cryptographic parameter. For example, in the case of elliptic curve cryptography defined by RFC5639, an API 111 for setting cryptographic parameters is prepared for each of p, A, B, x, y, q, and h.

The cryptographic operation unit 110 of the operating system 11, for the purpose of shortening the time required for the sequence executed by the application, performs multiple cryptographic operations without changing the cryptographic parameters. It is configured so that the process of inputting to is completed only once.

The cryptographic computation unit 110 uses a check code, which is data indicating characteristics of the cryptographic parameters, to confirm the identity of the cryptographic parameters. In this embodiment, confirming the identity of the cryptographic parameters means confirming whether the cryptographic parameters passed from the application 12 and input to the cryptographic coprocessor 106 are the same as the cryptographic parameters set in the cryptographic calculation unit 110. means that As check codes that indicate the characteristics of cryptographic parameters, for example, error detection codes such as CRC (Cyclic Redundancy Check) calculated by polynomials and hash values calculated from hash functions such as SHA2 (Secure Hash Algorithm) can be used. can be done.

When cryptographic parameters are input to the cryptographic computation coprocessor 106, the cryptographic computation unit 110 stores the check code of the cryptographic parameters in the memory as a check code for identity verification so that the identity of the cryptographic parameters can be verified. Although the check code for identity confirmation is generally stored in the RAM 102 , the check code for identity confirmation can also be stored in the NVM 103 .

The cryptographic operation unit 110 inputs the cryptographic parameters to the cryptographic operation coprocessor 106 when the cryptographic parameters delivered from the application 12 are stored in the memory as a check code for identity confirmation. The encryption parameter check code delivered from the application 12 before is compared with the identity confirmation check code stored in the memory at this time. If these check codes match, the cryptographic operation unit 110 determines that the cryptographic parameters handed over from the application 12 have been input to the cryptographic operation coprocessor 106 and does not input the cryptographic parameters to the cryptographic operation coprocessor 106 .

FIG. 3 is a diagram for explaining the operation of the cryptographic computation unit 110 included in the secure element 1. As shown in FIG. The cryptographic calculation unit 110 is activated when the application 12 calls one of the APIs 111, and diverges and branches the processing depending on the type of the API 111 called by the application 12 (S1).

When the API 111 called by the application 12 is the API 111 for setting cryptographic parameters, the cryptographic computation unit 110 executes processing (S2) related to cryptographic parameter settings. Arguments of the API 111 for setting cryptographic parameters include the types of cryptographic parameters and the cryptographic parameters themselves.

In the processing (S2) related to the setting of cryptographic parameters, the cryptographic calculation unit 110 first uses the API 111 to calculate the check code of the cryptographic parameters handed over from the application 12 (S20). For example, when a hash value is used for the check code, the cryptographic calculation unit 110 calculates the check code of the cryptographic parameter by substituting the cryptographic parameter into a hash function such as SHA2.

Next, the cryptographic operation unit 110 acquires from the memory a check code for identity confirmation corresponding to the type of cryptographic parameter delivered from the application 12 (S21), and performs processing depending on the presence or absence of the check code for identity confirmation. Branches (S22).

If the check code for identity confirmation does not exist in the memory, the cryptographic parameters have not been input to the cryptographic computation coprocessor 106, so the cryptographic computation unit 110 enters the cryptographic parameters into the cryptographic computation coprocessor 106 (S24). move on.

When the check code for identity confirmation exists in the memory, the cryptographic calculation unit 110 compares the check code calculated from the cryptographic parameters handed over from the application 12 with the check code for identity confirmation (S23).

If the check code calculated from the cryptographic parameters delivered from the application 12 matches the check code for identity confirmation, the cryptographic parameters delivered from the application 12 have already been input to the cryptographic computation unit 110 at this point. means that Therefore, in order to save the time required to input the cryptographic parameters, the cryptographic computation unit 110 does not input the cryptographic parameters handed over from the application 12 to the cryptographic computation coprocessor 106, and performs the processing (S2) related to the cryptographic parameter setting. finish.

If the check code calculated from the cryptographic parameters handed over from the application 12 does not match the check code for verifying identity, it means that the cryptographic parameters handed over from the application 12 and the input to the cryptographic calculation unit 110 at this time point. cipher parameters are different. Therefore, the cryptographic operation unit 110 inputs the cryptographic parameters handed over from the application 12 to the cryptographic operation coprocessor 106 in order to update the cryptographic parameters input to the cryptographic operation coprocessor 106 (S24). Next, in order to update the check code for identity confirmation, the cryptographic operation unit 110 updates the check code for identity confirmation stored in the memory in association with the type of encryption parameter passed from the application 12 to the application. 12 is executed to rewrite the check code calculated from the cryptographic parameters (S25), and the cryptographic parameter setting processing (S2) ends.

For example, if the cryptographic computation supported by the cryptographic computation unit 110 is the elliptic curve cryptography specified by RFC5639, at least p, A, B, x, y, and q are set for processing related to cryptographic parameter setting (S2 ) will be executed repeatedly. Note that since h is a 1-byte value, the verification of the identity of the encryption parameters may be omitted.

A case where the API 111 called by the application 12 is other than the API 111 for setting encryption parameters will be described.

When the API 111 called by the application 12 is the API 111 for setting the encryption key, the cryptographic calculation unit 110 executes the processing (S3) related to the setting of the encryption key. The argument of the API 111 for setting the encryption key includes the encryption key, and the encryption operation unit 110 inputs this encryption key to the encryption operation coprocessor 106, and ends the processing (S3) related to setting the encryption key.

When the API 111 called by the application 12 is the API 111 for setting the calculation target data, the cryptographic calculation unit 110 executes the processing (S4) related to the setting of the calculation target data. The argument of the API 111 for setting the calculation target data includes the calculation target data, and the cryptographic calculation unit 110 inputs this calculation target data to the cryptographic calculation coprocessor 106 to perform processing related to setting the calculation target data (S4). exit.

When the API 111 called by the application 12 is the API 111 for executing cryptographic calculation, the cryptographic calculation unit 110 executes processing (S5) related to execution of the cryptographic calculation. The argument of the API 111 for executing the cryptographic operation includes the type of cryptographic operation (encryption or decryption), and the cryptographic operation unit 110 inputs this type of cryptographic operation to the cryptographic operation coprocessor 106 to 106 to execute the cryptographic calculation, and the processing (S5) related to the execution of the cryptographic calculation ends.

1 Secure Element 10 Hardware 106 Cryptographic Operation Coprocessor 11 Operating System 110 Cryptographic Operation Unit 111 API
12 applications

Claims (1)

A cryptographic operation coprocessor that performs processing related to cryptographic operations that require cryptographic parameters that define mathematical expressions, and a cryptographic operation unit that performs the cryptographic operations using the cryptographic operation coprocessor, wherein the cryptographic operation unit When the cryptographic parameters are input to the cryptographic operation coprocessor, the check code of the cryptographic parameters is stored in the memory as the check code for identity confirmation, and in the state of being stored in the memory as the check code for identity confirmation, the When cryptographic parameters are input to the cryptographic operation coprocessor, before inputting the cryptographic parameters to the cryptographic operation coprocessor, a check code for the cryptographic parameters to be input to the cryptographic operation coprocessor and stored in memory at this time. The secure element compares the check codes for confirming identity that are stored in the secure element, and if the check codes match, the secure element performs an operation not to input the cryptographic parameter to the cryptographic operation coprocessor.

Images