Verification device, verification method, and program

Abstract

When obtaining an image digitally signed with C2PA, there is a problem in that the origin information cannot be displayed unless the root CA certificate of the accompanying public key certificate is possessed. [Solution] This concerns the case where the origin of an image to which C2PA is applied is displayed, and there is no issuer certificate to verify the legitimacy of the public key certificate associated with the C2PA image. In this case, if the public key certificate contains information about the certificate authority issuer in the institutional access information, the "root certificate" is traced from there, and an HTTPS certificate is obtained to verify the authenticity of the distribution destination. The origin is displayed only when this is possible.

Description

Technical Field

[0001] The present invention relates to a verification device and a verification method, and relates to a technology for verifying the authenticity of digital content.

Background Art

[0002] In recent years, creating fake images by tampering with digital content such as images and videos and deliberately spreading them on the Internet has become a social problem, causing individuals and companies to suffer damage from false information. To solve this problem, it is necessary to guarantee the authenticity (not being tampered with) of digital content, and for this, digital signatures, which are well-known technologies, can be used. Digital signatures use cryptographic techniques to assign digital signatures to digital content, and by verifying the digital signatures, the authenticity of the content can be confirmed. Enterprises and media organizations handling digital content have a high interest in a mechanism for providing authenticity guarantees. Therefore, C2PA (Coalition for Content Provenance and Authenticity) has been established by major enterprises and media organizations. C2PA standardizes a mechanism that can guarantee the authenticity and origin of digital content. By incorporating the data for authenticity guarantee defined in the C2PA standard as metadata into digital content, the verifiability of the authenticity and origin of digital content is established.

[0003] When performing digital signature verification, it is necessary to store the certificate of the root CA (Certification Authorities) in advance on the verification side.

[0004] Patent Document 1 describes a method of storing the certificate of the root CA and, when verifying the digital signature of a communication partner, performing on behalf the signature verification operation of verifying the certificate and confirming the validity of the certificate, and the operation of notifying the verification result.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2005-260759 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] To verify the authenticity and provenance of C2PA digital content, a root CA certificate is required to confirm the legitimacy of the public key associated with the C2PA image. However, in the case of C2PA, the root CA certificate depends on the organization, device, and user that generate the image, making it difficult to obtain all of these in advance.

[0007] Therefore, it is possible that the equipment used to verify C2PA digital content may not possess the root CA certificate necessary to confirm the legitimacy of the public key associated with that content. In this case, there is a problem in that the origin of the content cannot be verified, i.e., it cannot be made clear to the user. [Means for solving the problem]

[0008] According to one aspect of the present invention, a verification device for verifying content data comprising image data, a public key certificate, and signature data of the image data comprises: verification means for verifying the signature data with the public key contained in the public key certificate; first determination means for determining the validity of the certificate of the issuer of the public key certificate; second determination means for determining the validity of the issuer's certificate obtained based on the information shown in the public key certificate; and display means for displaying the verification result according to the validity determined by the second determination means, wherein if validity is confirmed by the first determination means, the determination by the second determination means is not performed, and if validity is not confirmed by the first determination means, the determination by the second determination means is performed. [Effects of the Invention]

[0009] According to the present invention, even if there is no root CA certificate to verify the legitimacy of the public key associated with the C2PA image, the origin can be displayed by utilizing the root CA certificate of the authority access information of the public key certificate. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram showing the configuration of C2PA image data and verification equipment. [Figure 2] A block diagram showing an example of the functional configuration of the verification device 101 in this embodiment. [Figure 3] A flowchart illustrating the process in the first embodiment. [Figure 4] A diagram showing the format of the certificate of this embodiment. [Figure 5] A flowchart illustrating the process in the second embodiment. [Modes for carrying out the invention]

[0011] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0012] <First Embodiment> [System Configuration] Figure 1 shows the relationship between C2PA image data and a verification device according to this embodiment. 101 is a PC, which is a verification device for verifying C2PA image data. Although a PC is shown here as an example of a verification device, other devices capable of displaying image data, such as smartphones and tablets, are also possible. 102 is image data in which data for authenticity assurance defined in the C2PA standard is incorporated into the digital content as metadata, and is an example of content data in this embodiment. This image data is generated by a digital camera compliant with the C2PA standard, a generative AI (Artificial Intelligence), or image editing software. Furthermore, although still image data is assumed in this explanation, video data generated by a video camera or the like may also be used.

[0013] The following describes a method for verifying the authenticity and provenance of image data 102 by performing digital signature verification using metadata embedded in image data 102 on PC 101, which has received image data 102, and displaying the results.

[0014] [Device Functional Configuration] Next, an example of the functional configuration of PC101 as a verification device according to this embodiment will be described. Note that the configuration of the functional blocks described below is merely an example. Some or all of the functional blocks described below may be replaced with other functional blocks that perform similar functions. Also, some functional blocks may be omitted, or further functional blocks may be added. Furthermore, one functional block shown in the following description may be divided into multiple functional blocks, or multiple functional blocks may be integrated into one functional block.

[0015] Figure 2 is a block diagram showing an example of the functional configuration of PC101 as a verification device in this embodiment.

[0016] In FIG. 2, the information processing device processing unit 201 is a part that functions as a PC, and is responsible for controlling each part of the PC 101 according to the input signal and the program described later, and display instructions for notifying the user to the display processing unit 208. Instead of the information processing device processing unit 201 controlling the entire device, a plurality of hardware may share the processing to control the entire device.

[0017] The storage unit 202 stores a control program executed by the information processing device processing unit 201, a certificate used for verification, and the like. Various operations described later are performed by the information processing device processing unit 201 executing the control program stored in the storage unit 202.

[0018] The storage unit 202 may include a main storage unit and an auxiliary storage unit. The main storage unit is, for example, a ROM (Read Only Memory), a RAM (Random Access Memory), or the like. The main storage unit may store or temporarily store programs and data such as an OS (Operating System) and application software, which are basic software executed by the information processing device processing unit 201. The auxiliary storage unit is, for example, an HDD (Hard Disk Drive), an SSD (Solid State Drive), or the like, and may store data related to application software. For example, a control program stored in a non-volatile storage area is expanded in a RAM (Random Access Memory) and executed by a processor constituting the information processing device processing unit 201. Thus, the information processing device processing unit 201 and the storage unit 202 may function as a so-called computer.

[0019] The memory unit 202 may include a recording medium that stores a predetermined program. The program stored in this recording medium is installed via a drive device or the like, and the installed predetermined program may be executable by the information processing device processing unit 201. Various types of recording media can be used as the recording medium. For example, the recording medium may be a recording medium that optically, electrically, or magnetically records information, such as a CD (Compact Disc)-ROM, a flexible disk, a magneto-optical disk, or the like. Also, the recording medium may be a semiconductor memory or the like that electrically records information, such as a ROM or a flash memory.

[0020] The digital verification processing unit 203 performs digital signature verification on the digital signature applied to the digital content using various certificates.

[0021] The issuer information acquisition unit 206 is a part that acquires information regarding the certificate issuer from the institution access information, which is the information included in the public key certificate. The processing content will be described below. FIG. 4 shows an example of a description example of a certificate. The public key certificate conforms to this certificate description format. As shown in the figure, there is an information area called "institution information access". Here, the location where the certificate of the certification authority of the certificate issuer is published is described in the illustrated format. The issuer information acquisition unit 206 has a function of acquiring the location where the certificate of the certification authority of the issuer is published from "institution information access".

[0022] The issuer information analysis unit 204 analyzes the reliability of the information regarding the issuer acquired by the issuer information acquisition unit 206. Details will be described later.

[0023] The communication unit 207 is a wired or wireless communication interface for communicating with an external device. In the present embodiment, communication processing related to the acquisition process of the image data 102 and the acquisition process of the certificate required for digital signature verification is performed.

[0024] The display processing unit 208 is responsible for the display function of the PC 101, displaying image data 102 and history information in accordance with the C2PA standard contained in the image data 102. The PC 101 includes a display unit composed of, for example, a liquid crystal display or an LED (Light Emitting Diode), and also includes a speaker and other notification devices.

[0025] [Example of processing] An example of the operation of this embodiment will be explained using the flowchart shown in Figure 3.

[0026] In Figure 1, PC101 obtains image data 102 compliant with the C2PA standard via the communication unit 207 and other means, and imports it into its own device (S301). PC101 checks the metadata, which is C2PA information, associated with the image data 102 in order to confirm the origin information of the image data 102 in the digital verification processing unit 203. Specifically, it first checks that a public key certificate exists in the metadata (S302). Furthermore, PC101 uses the public key certificate to perform digital signature verification on the metadata associated with the image data 102 in order to confirm the origin information of the image data 102 in the digital verification processing unit 203 (S303). If the digital signature verification fails at this point, it can be determined that the image data 102 has been tampered with in some way, and a message to that effect is displayed to the user (S309).

[0027] If the digital signature verification is successful, the PC101's digital verification processing unit 203 verifies the reliability of the public key certificate used for digital signature verification. Specifically, it verifies the issuer of the certificate to confirm its legitimacy. That is, it checks whether the PC101 possesses the target root CA certificate and whether the certificate is suitable for digital signature verification (S304). If the PC101 confirms that it possesses the root CA certificate, the reliability of the public key certificate is guaranteed. Therefore, the origin information of the image data 102 is reliable, and the origin information is displayed to the user (S310).

[0028] Now, let's assume that PC101 does not possess the root CA certificate for the issuer of the aforementioned public key certificate. In this case, the provenance information of image data 102 cannot be trusted at this time.

[0029] In this case, the PC 101 uses the issuer information acquisition unit 206 to check whether the "authority access information" of the public key certificate contains information about the location where the certificate issued by the certification authority publishes the certificate (S305). If there is no information about the issuing certification authority, the reliability of the public key signature cannot be guaranteed. Therefore, the user is notified that it is not possible to display the origin information of the image data 102 (S311).

[0030] If information regarding the issuer of the public key certificate is available, the certificate of the issuing authority is obtained. The certificate acquisition process is performed using HTTPS (Hypertext Transfer Protocol Secure) (S306). If the certificate cannot be obtained via HTTPS, the user is notified that the reliability of the certificate cannot be confirmed and therefore the origin information of image data 102 cannot be displayed.

[0031] If the certificate is obtained (S307), this public location can be accessed via SSL (Secure Sockets Layer) / TLS (Transport Layer Security) communication. In other words, the certificate confirms that the public key certificate used for SSL / TLS communication is treated as a trusted certificate.

[0032] Furthermore, PC101 verifies whether the certificate obtained by the issuer information analysis unit 204 is a root CA certificate. If it is not a root CA certificate but an intermediate certificate, PC101 uses the issuer information acquisition unit 206 to obtain the location where the certificate of the issuing certification authority is published from the "authority access information" of the intermediate certificate, and then obtains the certificate. By repeating these processes, the root CA certificate is obtained (S308).

[0033] As described above, by obtaining the issuer information from the public key certificate via HTTPS, the reliability of the alternative root CA certificate can be guaranteed. Therefore, we have decided to replace this certificate as the root CA certificate in the C2PA digital signature.

[0034] PC101 displays the provenance information for image data 102 to the user, along with a statement that its reliability has been ensured by using an alternative certificate in the digital signature verification (S312). For example, it could display the C2PA provenance information alongside the message, "An alternative security certificate was used to verify this provenance information." Alternatively, the UI could be configured to display the provenance information only after obtaining consent to use an alternative certificate. Furthermore, it could prompt the user to obtain the certificate of the issuer of the public key certificate and perform digital signature verification again.

[0035] As described above, when the verification device does not possess the root CA certificate relating to the issuer of the public key certificate used for digital signature verification, it is possible to display the origin information of the C2PA image by using an alternative root CA certificate.

[0036] <Other Embodiments> In the first embodiment, the case where the root CA certificate of the public key certificate used for digital signature verification is not available in the digital signature verification process of image data 102 compatible with C2PA on PC 101 was described. The method described was to notify the user that reliability had been ensured by using an alternative certificate.

[0037] In this embodiment, the "extended key usage" information in the root CA certificate is utilized to provide users with further information.

[0038] [Device Functional Configuration] The system configuration in this embodiment is the same as in Figure 1, but a description of the trust information processing unit 205 is added. This processing unit acquires the "extended key usage" information held by the root CA certificate. An example of the "extended key usage" is shown in the certificate description example in Figure 4, where the "extended key usage" contains information on the key's purpose. The trust information processing unit 205 is the processing unit that acquires this information. The other processing units are the same as in the first embodiment, so their description is omitted here.

[0039] (Example of processing) An example of the operation of this embodiment will be explained using the flowchart shown in Figure 5.

[0040] In this embodiment as well, the PC101 in Figure 1 obtains image data 102 corresponding to the C2PA standard and performs the process of confirming the origin information of the image data 102 (S501).

[0041] In this embodiment, during the process of verifying the provenance information of the image data 102, digital signature verification is possible (S502, S503), and the system does not possess the certificate of the issuer of the public key certificate for said verification (S504). On the other hand, if digital signature verification is not possible, a message indicating that tampering has been detected is displayed (S510).

[0042] Furthermore, access to the authority information of a public key certificate includes information about the issuer of the certificate (S505), and it is assumed that access to the publicly available destination of the acquired root CA certificate is possible via HTTPS communication (S506, S507, S508). Other processing is the same as in the first embodiment, so it will not be explained here.

[0043] PC101 has confirmed that the acquired root CA certificate is treated as a trusted root CA certificate by the public key certificate used for SSL / TLS communication. Therefore, it is decided to substitute this root CA certificate as the root CA certificate in the C2PA digital signature.

[0044] Furthermore, PC101, in the Trust Information Processing Unit 205, obtains information regarding the purpose of the root certificate from the "Extended Key Usage" of the root certificate (S509).

[0045] If the information obtained here is for a purpose undesirable as a substitute for displaying C2PA history information, such as only "client authentication," the root certificate in question will be removed as a substitute certificate. PC101 notifies the user that it is not possible to display the history information of image data 102 (S511).

[0046] On the other hand, if the acquired information is deemed suitable as a substitute for displaying C2PA history information, such as "server authentication," then the root certificate in question will be adopted as the alternative certificate.

[0047] PC101 displays the provenance information of the image data 102 to the user, along with the alternative certificate used in the digital signature verification and the purpose for which the certificate was intended (S512). In addition to the user notification content described in the first embodiment, it is possible to display, for example, "This provenance information verification uses a site access security certificate."

[0048] As described above, in addition to the effects of the first embodiment, by notifying the user of the purpose of the alternative root CA certificate, it becomes possible to communicate the reasons for the decision to use the alternative.

[0049] (Other embodiments) Although examples of embodiments have been described in detail above, the present invention can take the form of, for example, a system, apparatus, method, program, or recording medium (storage medium). Specifically, it may be applied to a system consisting of multiple devices (for example, a host computer, interface devices, imaging devices, web applications, etc.), or to an apparatus consisting of a single device.

[0050] Furthermore, it goes without saying that the object of the present invention is achieved as follows: a recording medium (or storage medium) containing program code (computer program) of software that realizes the functions of the embodiments described above is supplied to a system or device. Such storage medium is, needless to say, a computer-readable storage medium. The computer (or CPU or MPU) of the system or device then reads and executes the program code stored on the recording medium. In this case, the program code read from the recording medium itself realizes the functions of the embodiments described above, and the recording medium containing that program code constitutes the present invention. [Explanation of symbols]

[0051] 204 Publisher Information Analysis Department 205 Reliability Information Processing Unit 206 Issuer Information Acquisition Department

Claims

1. A verification device for verifying content data comprising image data, a public key certificate, and data for the signature of the image data, A verification means for verifying the signature data with the public key contained in the public key certificate, A first determination means for determining the validity of the certificate of the issuer of the public key certificate, A second determination means for determining the validity of the issuer's certificate obtained based on the information shown in the public key certificate, The system includes a display means for displaying the results of the verification in accordance with the effectiveness based on the second determination means, If effectiveness is confirmed by the first determination method, the determination by the second determination method will not be performed. A verification device characterized in that, if effectiveness cannot be confirmed by the first determination means, a determination is made by the second determination means.

2. The verification apparatus according to claim 1, characterized in that the image data includes image metadata.

3. The verification apparatus according to claim 1, characterized in that the metadata of the image includes the history information of the image data.

4. The verification device according to claim 1, characterized in that the first determination means has a plurality of trusted certificates and determines validity based on whether or not the certificate of the issuer of the public key certificate is included in the plurality of certificates.

5. The verification device according to claim 1, characterized in that the first determination means verifies the digital signature of the issuer's certificate and determines its validity based on the result of the verification.

6. The verification device according to claim 1, characterized in that the first determination means determines validity based on the contents of the issuer's certificate.

7. The verification device according to claim 1, characterized in that the second determination means determines validity based on the method of acquisition and the contents of the certificate of issuer obtained.

8. The verification device according to claim 1, characterized in that the second determination means determines validity based on the contents of the issuer's certificate.

9. The verification device according to claim 1, characterized in that the second determination means determines the validity of a certificate obtained using HTTPS.

10. The verification device according to claim 1, characterized in that the display means displays the verification result when the effectiveness is confirmed by the first determination means.

11. The verification apparatus according to claim 1, characterized in that the display means displays, in addition to the verification results, a fact when effectiveness cannot be confirmed by the first determination means and effectiveness can be confirmed by the second determination means.

12. If the effectiveness of the display means cannot be confirmed by either the first determination means or the second determination means, The verification device according to claim 1, characterized in that it displays a statement indicating that the validity of the verification results cannot be confirmed.

13. A verification method for verifying content data comprising image data, a public key certificate, and data for the signature of the image data, A verification step in which the signature data is verified using the public key contained in the public key certificate, A first determination step in which the validity of the certificate of the issuer of the public key certificate is determined, A second determination step involves determining the validity of the issuer's certificate obtained based on the information shown in the aforementioned public key certificate, The system includes a display step in which the results of the verification are displayed on a display unit according to the effectiveness based on the second judgment step, If effectiveness is confirmed in the first judgment step, the judgment in the second judgment step is not performed. A verification apparatus characterized in that if effectiveness cannot be confirmed in the first determination step, the determination step in the second determination step is performed.

14. A program for operating a computer as a verification device according to any of claims 1 to 12.

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