Information processing device and information processing method

Abstract

A purpose of the present invention is to prevent a third party from illegally obtaining confidential information or fragments for restoring confidential information.　An isolated environment according to the present invention allows for recovery of confidential information from a prescribed number of fragments or division of confidential information into a prescribed number of fragments. For example, the isolated environment may include a secure element unit or a TEE portion. For example, when restoring confidential information from a plurality of fragments, the isolated environment may use fragments stored in the isolated environment and fragments input to the isolated environment from outside. Furthermore, when restoring confidential information from a plurality of fragments, for example, the isolated environment may use a plurality of fragments that are input to the isolated environment from outside. In this case, at least some of the fragments input from outside into the isolated environment may be encrypted.

Description

Information Processing Apparatus and Information Processing Method

[0001] The present technology relates to an information processing apparatus and an information processing method, and more particularly, to an information processing apparatus that handles secret information.

[0002] Conventionally, a secret sharing technique has been known for dividing secret information such as signature key data into a plurality of fragments (shares) and storing them分散保存して、複数の断片が集まらないと元の秘密情報を復元できないようにする (for example, see Patent Document 1). As a secret sharing method, for example, Shamir's secret sharing method is known.

[0003] In this case, when dividing into n fragments, it is also possible to set so that the original secret information can be restored by collecting at least t of them. Thereby, confidentiality and availability are realized. Confidentiality means preventing secret information from being known to a third party, and availability means preventing secret information from being lost. In this case, even if up to t - 1 fragments are known to a third party, the secret information cannot be restored, and even if up to n - t fragments are lost, the secret information can be restored.

[0004] International Publication No. 2024 / 063

[0005] An object of the present technology is to suppress a third party from illegally acquiring secret information or fragments for restoring secret information.

[0006] The concept of the present technology resides in an information processing apparatus having an isolation environment for restoring secret information from a predetermined number of fragments or dividing secret information into a predetermined number of fragments.

[0007] In the present technology, the isolation environment performs restoration of secret information from a predetermined number of fragments or division of secret information into a predetermined number of fragments. For example, the isolation environment may be configured to include a secure element part or a TEE part.

[0008] For example, when restoring confidential information from multiple fragments, the isolation environment may use fragments stored in the isolation environment and fragments input to the isolation environment from an external source. In this case, not all of the multiple pieces of confidential information involved in the restoration are input from an external source, making it possible to prevent a third party from knowing all of the multiple pieces of confidential information involved in the restoration and restoring the confidential information.

[0009] In this case, for example, the secret information may be divided into n fragments, and the secret information can be reconstructed by assembling at least t fragments, and the number of fragments stored in the isolation environment may be s > n - t. This ensures that the secret information cannot be reconstructed unless there are fragments stored in the isolation environment. Here, for example, the number of fragments input into the isolation environment from the outside may be r, and the number of fragments s + r ≥ t. This makes it possible to reconstruct the secret information from the fragments stored in the isolation environment and the fragments input into the isolation environment from the outside.

[0010] Furthermore, for example, when recovering confidential information from multiple fragments, the isolation environment may use multiple fragments input to the isolation environment from an external source. In this case, it becomes unnecessary to store the multiple fragments involved in recovering the confidential information in the isolation environment. In this case, for example, at least some of the multiple fragments input to the isolation environment from an external source may be encrypted, and the isolation environment may decrypt and use the encrypted fragments. In this case, it becomes possible to deter a third party from recovering the confidential information by knowing all of the multiple pieces of confidential information involved in the recovery.

[0011] Furthermore, for example, when dividing confidential information into multiple fragments, the isolation environment may be configured to further generate the confidential information. In this case, the confidential information is generated within the isolation environment, making it possible to deter third parties from illegally obtaining the confidential information.

[0012] Furthermore, for example, when recovering confidential information from multiple fragments, the isolation environment may be configured to allow for further use of the confidential information. In this case, the confidential information is used within the isolation environment, making it possible to deter third parties from illegally obtaining the confidential information.

[0013] Furthermore, for example, the isolation environment may send some of the multiple fragments obtained from the partitioning of confidential information to an external device via an encrypted communication channel or after encryption. In this case, for example, the external device may include a device or cloud equipped with the isolation environment. This makes it possible to deter a third party from illegally obtaining some of the multiple fragments when they are sent to the external device.

[0014] Thus, this technology involves restoring confidential information from a predetermined number of fragments, or dividing confidential information into a predetermined number of fragments, in an isolated environment, making it possible to prevent third parties from illegally obtaining confidential information or the fragments needed to restore it.

[0015] Another concept of this technology lies in information processing methods that perform the reconstruction of confidential information from multiple fragments, or the division of confidential information into multiple fragments, in an isolated environment.

[0016] Another concept of this technology is an information processing device comprising an isolation environment for storing multiple fragments obtained by partitioning confidential information, the isolation environment for transmitting at least a portion of the multiple fragments to an external device via an encrypted communication channel or in an encrypted state.

[0017] In this technology, multiple fragments obtained by partitioning confidential information are stored in an isolated environment. The isolated environment then transmits at least some of these fragments to an external device via an encrypted communication channel or in an encrypted state. For example, the isolated environment may include a secure element unit or a TEE unit. Also, for example, the external device may include a device or cloud equipped with an isolated environment. Furthermore, for example, the isolated environment may delete fragments transmitted to the external device from the isolated environment.

[0018] In this technology, at least a portion of multiple fragments is transmitted to an external device via an encrypted communication channel or encrypted, making it possible to prevent a third party from illegally obtaining a portion of the multiple fragments when it is sent to the external device.

[0019] Another concept of this technology is an information processing device that includes an isolation environment for storing multiple fragments obtained by partitioning confidential information, and the isolation environment for assigning authentication information to at least some of the multiple fragments.

[0020] In this technology, multiple fragments obtained by partitioning confidential information are stored in an isolated environment. Furthermore, authentication information is attached to at least some of these fragments within the isolated environment. This ensures that even if a third party gains unauthorized access to the isolated environment, unauthorized acquisition of the fragments with attached authentication information is deterred.

[0021] Another concept of this technology is an information processing device that includes an isolation environment for storing multiple fragments obtained by partitioning confidential information, and the isolation environment for assigning usage information to at least some of the multiple fragments.

[0022] In this technology, multiple fragments obtained by partitioning confidential information are stored in an isolated environment. Furthermore, the isolated environment assigns usage information to at least some of these fragments. This makes it possible to deter unauthorized use by a third party even if they gain unauthorized access to the isolated environment, as the fragments with assigned usage information are protected.

[0023] Figure 1 is a block diagram illustrating an example configuration of an information terminal to which this technology can be applied. Figure 2 is a diagram illustrating Embodiment 1 (Recovery of confidential information in an isolated environment). Figure 3 is a diagram illustrating Embodiment 1 (Recovery of confidential information in an isolated environment). Figure 4 is a diagram illustrating Embodiment 2 (Storage of fragments in an isolated environment). Figure 5 is a diagram illustrating Embodiment 2 (Encryption of fragments for input in an isolated environment). Figure 6 is a diagram illustrating Embodiment 3 (Transmission of fragments using an encrypted communication channel from an isolated environment). Figure 7 is a diagram illustrating Embodiment 3 (Transmission of fragments using encryption from an isolated environment). Figure 8 is a diagram illustrating Embodiment 4 (Dividing into fragments in an isolated environment). Figure 9 is a diagram illustrating Embodiment 5 (Assigning authentication information to fragments in an isolated environment). Figure 10 is a diagram illustrating Embodiment 6 (Assigning usage information to fragments in an isolated environment). Figure 11 is a diagram schematically showing an example of an application example of this technology. Figure 12 is a diagram illustrating Procedure 1 (Generation of a signature key and division into fragments) in an application example to a crypto asset signature key. Figure 13 is a diagram illustrating step 2 (fragment transfer) in an application example to a cryptocurrency signing key. Figure 14 is a diagram showing an example sequence related to step 1 (signing key generation and division into fragments) and step 2 (fragment transfer). Figure 15 is a diagram illustrating step 3 (signing key utilization) in an application example to a cryptocurrency signing key. Figure 16 is a diagram showing an example sequence related to step 3 (signing key utilization). Figure 17 is a diagram illustrating step 2' (management of encryption fragments outside the secure element) in an application example to a cryptocurrency signing key. Figure 18 is a diagram showing an example sequence related to step 2' (management of encryption fragments outside the secure element). Figure 19 is a diagram illustrating step 3' (signing key utilization) in an application example to a cryptocurrency signing key. Figure 20 is a diagram showing an example sequence related to step 3' (signing key utilization).

[0024] The following describes embodiments for carrying out the invention (hereinafter referred to as "embodiments"). The description will be in the following order: 1. Embodiments 1-1. Example of information terminal configuration 1-2. Embodiment 1 (Recovery of confidential information in an isolated environment) 1-3. Embodiment 2 (Storage of fragments in an isolated environment, encryption of fragments for input to an isolated environment) 1-4. Embodiment 3 (Encrypted communication channel from an isolated environment and transmission of fragments using encryption) 1-5. Embodiment 4 (Dividing into fragments in an isolated environment) 1-6. Embodiment 5 (Assigning authentication information to fragments in an isolated environment) 1-7. Embodiment 6 (Assigning authentication information to fragments in an isolated environment) 1-8. Examples of application of this technology 2. Modified examples

[0025] <1. Embodiments> "1-1. Example of Information Terminal Configuration" Figure 1 shows an example of the configuration of an information terminal 100 to which this technology can be applied. The information terminal 100 includes, for example, a mobile terminal such as a smartphone, or a personal computer.

[0026] The information terminal 100 includes a control unit 101, a storage unit 102, a memory unit 103, an input unit 104, an output unit 105, a secure element unit 106, an NFC (Near Field Communication) communication unit 107, and a network communication unit 108. The control unit 101 has a processor. Each function of the information terminal 100 is realized by a control program that runs on the processor.

[0027] The secure element unit 106 is composed of, for example, an eSE (embedded Secure Element), which is a Secure Element (SE) chip, in a mobile terminal. The control unit 101 includes a Trusted Execution Environment (TEE) unit 109 that provides a reliable execution environment. Here, the secure element unit 106 and the TEE unit 109 are examples of an isolated environment that cannot be accessed by third parties (hereinafter referred to as "isolated environment" as appropriate).

[0028] In the following descriptions of specific examples in each embodiment, we will use the case where the information terminal 100 is a smartphone 100A and the isolated environment is the secure element unit 106 as an example. Of course, this technology can be applied even if the information terminal 100 is an information device other than a smartphone 100A, and it can also be applied even if the isolated environment is the TEE unit 109 or other similar functional unit.

[0029] "1-2. Embodiment 1 (Restoration of Confidential Information in an Isolated Environment)" For example, if the confidential information is a signing key, confidentiality during storage can be achieved by dividing the confidential information into multiple fragments (shares) and storing them in a distributed manner. However, when attempting to sign (digitally sign) using the confidential information, the confidential information must be restored from the multiple fragments, and in doing so, there is a possibility that the confidential information may be known to a third party. Generally, when using confidential information, it must be restored from multiple fragments, and when it is restored, the confidential information may be known to a third party.

[0030] Therefore, in Embodiment 1, multiple fragments are input into an isolated environment that cannot be accessed by a third party, and confidential information is reconstructed from these fragments within this isolated environment. Examples of the isolated environment include the secure element unit 106 and the TEE unit 109, as described above. This isolated environment may be designed so that even the owner of the isolated environment cannot access it except through predetermined procedures.

[0031] Furthermore, in Embodiment 1, the restored confidential information is used without leaving the isolated environment. Examples of use include digital signatures and fragmentation. An example of fragmentation is when confidential information that has been divided into three parts is to be divided into four parts to improve availability. In this case, the confidential information must be restored once and then divided into fragments again. Also, the restoration and use of confidential information may be performed inseparably; that is, after the restoration of confidential information, it may be possible to use the confidential information once for one purpose, or it may be possible to use the confidential information multiple times or for multiple purposes after the restoration.

[0032] Figure 2(a) shows an example of recovering and using confidential information on an application in a smartphone (hereinafter referred to as "smartphone") 100A. In this example, confidential information is recovered from two fragments, 1 and 2, on the application, and the recovered confidential information (signing key) is then used for signing on the application. In this case, an attacker on the application can obtain the confidential information.

[0033] Figure 2(b) shows an example in which the secure element unit 106 of a smartphone 100A recovers and uses confidential information. In this example, two fragments, fragment 1 and fragment 2, are input to the secure element unit 106 from an external source. The secure element unit 106 recovers confidential information from the two fragments, fragment 1 and fragment 2. Furthermore, the secure element unit 106 creates a signature based on the confidential information (signing key), and this signature is then sent from the secure element unit 106 to the outside for use. In this case, the confidential information is recovered by the secure element unit 106 and used by the secure element unit 106, and is not sent to the outside, making it impossible for an attacker to obtain the confidential information.

[0034] In the examples in Figures 2(a) and 2(b), we show an example where a smartphone user (hereinafter referred to as "smartphone user") uses their own confidential information on their smartphone 100A. However, it is also possible that a smartphone user may use another person's (such as a business operator's) confidential information on their smartphone 100A. In that case, the other person does not want the smartphone user to know their confidential information. In the examples in Figures 3(a) and 3(b), we show an example where a smartphone user uses another person's confidential information on their smartphone 100A.

[0035] Figure 3(a) shows an example in which confidential information is recovered and used on an application in a smartphone 100A. In this case, it is the same as the example in Figure 2(a), and the smartphone user can obtain confidential information (confidential information of others). On the other hand, Figure 3(b) shows an example in which confidential information is recovered and used on a secure element unit 106 in a smartphone 100A. In this case, it is the same as the example in Figure 2(b), and the smartphone user cannot obtain confidential information (confidential information of others).

[0036] In the specific examples of the following embodiments, the confidential information is assumed to be the user's own confidential information, but it is also possible that this confidential information belongs to another party. In that case, the "attacker" would be replaced by the "smartphone user."

[0037] "1-3. Embodiment 2 (Storage of Fragments in an Isolated Environment, Encryption of Fragments Input to the Isolated Environment)" As in Embodiment 1 described above, when multiple fragments are input into an isolated environment that cannot be accessed by a third party, and confidential information is restored from the multiple fragments in this isolated environment, there is a possibility that the confidential information may be restored by a third party if the number of fragments necessary to restore the confidential information becomes known to the third party when the fragments are input into the isolated environment.

[0038] Therefore, in Embodiment 2, s fragments are stored in advance in an isolated environment that cannot be accessed by third parties. For example, s > n - t. Here, the secret information is divided into n fragments, and the secret information can be restored by collecting at least t fragments. By setting s > n - t, the secret information cannot be restored unless there are fragments stored in the isolated environment.

[0039] Furthermore, in Embodiment 2, r fragments such that s + r ≥ t are input to the isolated environment from the outside, and the secret information is restored by combining them with the fragments stored in the isolated environment. In this case, if r is chosen such that r < t, even if a third party knows the r fragments input to the isolated environment from the outside, they will not be able to restore the secret information. Here, when s > n - t, then r < t.

[0040] Figure 4(a) shows an example in which, in a smartphone 100A, multiple fragments necessary for restoring confidential information are input to the secure element unit 106 from an external source, and the secure element unit 106 restores the confidential information from the multiple fragments input from the external source. In this example, two fragments, fragment 1 and fragment 2, are input to the secure element unit 106 from an external source, and the secure element unit 106 restores the confidential information from the two fragments, fragment 1 and fragment 2, which is then used for signing. In this case, an attacker on the application can collect the two fragments, fragment 1 and fragment 2, when they are input to the secure element unit 106 from an external source, and can restore and learn the confidential information.

[0041] Figure 4(b) shows an example in a smartphone 100A where the secure element unit 106 has pre-stored parts of multiple fragments necessary for restoring the secret information, and the secret information is restored from those parts and other parts of the multiple fragments necessary for restoring the secret information that are input from the outside. In this example, one fragment 2 is stored in the secure element unit 106, one fragment 1 is input to the secure element unit 106 from the outside, and the secret information is restored in the secure element unit 106 from the two fragments 1 and 2 and used for digital signature. In this case, an attacker on the application can only collect one fragment 1 that is input to the secure element unit 106 from the outside, and cannot collect the other fragment 2, making it impossible for them to restore and learn the secret information.

[0042] As described above, an example was explained in which some of the multiple fragments necessary for restoring the confidential information are stored in the isolated environment beforehand, thereby preventing a third party from knowing the necessary number of fragments and restoring the confidential information when fragments are input into the isolated environment from the outside. However, it is also conceivable to encrypt at least some of the fragments input into the isolated environment from the outside, thereby preventing a third party from knowing those fragments when they are input into the isolated environment from the outside and thus preventing the restoration of the confidential information. In this case, the isolated environment holds the decryption key.

[0043] Fig. 5(a) is the same as Fig. 4(a), and its description will be omitted. Fig. 5(b) shows an example in the smartphone 100A where a plurality of fragments necessary for restoring secret information are input to the secure element unit 106 from the outside in an encrypted state, and the secure element unit 106 decrypts the plurality of fragments input from the outside and then restores the secret information. In this example, two fragments 1 and 2 are input to the secure element unit 106 from the outside in an encrypted state, and after the two fragments 1 and 2 are decrypted by the secure element unit 106, the secret information is restored and used for signing. In this case, on the application, since the attacker cannot collect the two fragments 1 and 2 when they are input to the secure element unit 106 from the outside because they are encrypted, it is impossible to restore and know the secret information.

[0044] In Fig. 5(b), both the fragment 1 and the fragment 2 input to the secure element unit 106 are encrypted, but only one of the fragment 1 and the fragment 2 may be encrypted. In that case, the attacker cannot collect the encrypted fragment, and it is impossible to restore and know the secret information.

[0045] "1-4. Embodiment 3 (Fragment transmission using an encrypted communication path or encryption from an isolated environment)" When fragments are stored in an isolated environment, if the isolated environment is lost due to loss, destruction, etc., it may be impossible to collect the fragments necessary for restoring the secret information, and the secret information may not be restored. To prevent this, when transmitting and storing fragments in a location different from the isolated environment (which may or may not be an isolated environment), there is a possibility that a third party may obtain the fragments when they are taken out of the isolated environment. Here, as an example of the isolated environment being lost due to loss, destruction, etc., loss of the information terminal itself having the isolated environment or electrical failure, etc. can be considered.

[0046] Therefore, in Embodiment 3, when a fragment is stored in an isolated environment, an encrypted communication channel is established between the isolated environment and a different location (an isolated environment or device), and the fragment is sent and stored at that location via the encrypted communication channel. At this time, either simultaneously with the transmission of the fragment or not, it is conceivable to erase the fragment from the original isolated environment. In the case of erasure, it means the movement of the fragment, and in the case of not erasing, it means the transmission of a copy of the fragment.

[0047] FIG. 6(a) shows an example in the smartphone 100A in which a fragment stored in the secure element unit 106 is taken out from the secure element unit 106 and sent to another device 200. In this example, the secret information is divided into three fragments: fragment 1, fragment 2, and fragment 3, and two of them, fragment 2 and fragment 3, are stored in the secure element unit 106. Fragment 3 is taken out from the secure element unit 106 and sent to another device 200 for storage. In this case, on the application, an attacker can obtain the fragment 3 when the fragment 3 is taken out from the secure element unit 106. Incidentally, fragment 1 is stored, for example, in the cloud.

[0048] FIG. 6(b) shows an example in the smartphone 100A in which a fragment stored in the secure element unit 106 is sent to another device 200 via an encrypted communication channel established between the secure element unit 106 and another device 200. In this example, similar to the example of FIG. 6(a), the secret information is divided into three fragments: fragment 1, fragment 2, and fragment 3, and two of them, fragment 2 and fragment 3, are stored in the secure element unit 106. And in this example, fragment 3 is sent and stored in another device 200 from the secure element unit 106 via an encrypted communication channel established between the secure element unit 106 and another device 200. In this case, since fragment 3 is sent from the secure element unit 106 to another device 200 via an encrypted communication channel, it is impossible for an attacker to obtain the fragment 3 on the application.

[0049] In the above example, we showed how to prevent a third party from obtaining a fragment when it is retrieved from an isolated environment by sending the fragment, which is stored in an isolated environment, to a different location (another isolated environment or device) via an encrypted communication channel. However, it is also conceivable to prevent a third party from obtaining a fragment when it is retrieved from an isolated environment by encrypting the fragment, which is stored in an isolated environment, and sending it to a different location (another isolated environment or device). In this case, another device 200 holds the decryption key.

[0050] Figure 7(a) is the same as Figure 6(a), so its explanation will be omitted. Figure 7(b) shows an example in which a fragment stored in the secure element unit 106 of a smartphone 100A is encrypted and sent to another device 200. In this example, similar to the example in Figure 7(a), that is, Figure 6(a), the secret information is divided into three fragments 1, 2, and 3, and two of these, fragments 2 and 3, are stored in the secure element unit 106. In this example, fragment 3 is encrypted in the secure element unit 106, and the encrypted fragment 3 is sent from the secure element unit 106 to another device 200, where it is decrypted and stored. In this case, since fragment 3 is encrypted and sent from the secure element unit 106 to the other device 200, it becomes impossible for an attacker to obtain fragment 3 on the application.

[0051] "1-5. Embodiment 4 (Partitioning into Fragments in an Isolated Environment)" When generating secret information such as a private key in a public-key cryptography scheme, a method is known in which the generation of the secret information is performed in an isolated environment, and the secret information itself cannot be taken out of the isolated environment, in order to eliminate the possibility that the generated secret information may be known to a third party. For example, in the case of a private key in a public-key cryptography scheme, the public key that is paired with the private key can be taken out of the isolated environment, but the private key cannot be taken out. If one attempts to perform the partitioning of secret information into fragments outside of the isolated environment, there is a possibility that the secret information may be known to a third party.

[0052] Therefore, in Embodiment 4, the division of confidential information into fragments is performed in an isolated environment. In this case, for example, the generation of confidential information and the division of this confidential information into fragments may be performed inseparably in the isolated environment, or confidential information input from outside the isolated environment may be divided into fragments in the isolated environment. Furthermore, some of the fragments obtained by dividing the confidential information in the isolated environment may be made available for external extraction from the isolated environment. In this case, as in Embodiment 2 described above, for example, s fragments may be left in the isolated environment, and the remaining fragments may be made available for external extraction.

[0053] Furthermore, fragments obtained by dividing confidential information in an isolated environment may be made available for transmission to a different location (an isolated environment or device). In this case, as in Embodiment 3 described above, the transmission from the isolated environment to the other location may be done using an encrypted communication channel or encryption, or it may be a copy with a portion remaining in the isolated environment, or it may be a transfer that erases a portion from the isolated environment.

[0054] Figure 8(a) shows an example in which the division of confidential information into fragments is performed outside the secure element unit 106, for example, on an application, in a smartphone 100A. In this example, the confidential information is divided into two fragments, fragment 1 and fragment 2, outside the secure element unit 106, and these two fragments, fragment 1 and fragment 2, are input into the secure element unit 106. In this case, since the division of confidential information into fragments is performed outside the secure element unit 106, an attacker can obtain the confidential information.

[0055] Figure 8(b) shows an example in which the secure element unit 106 performs the division of confidential information into fragments in a smartphone 100A. In this example, the secure element unit 106 generates confidential information and further divides this confidential information into two fragments, fragment 1 and fragment 2. In this case, since the secure element unit 106 generates the confidential information and then divides it into fragments, it becomes impossible for an attacker to obtain the confidential information.

[0056] "1-6. Embodiment 5 (Assigning Authentication Information to Fragments in an Isolation Environment)" If a third party illegally accesses the isolation environment, they may use fragments that were entered into the isolation environment before access or fragments stored thereto to recover confidential information, use the recovered confidential information, or transmit the fragments to other isolation environments or devices.

[0057] Therefore, in Embodiment 5, authentication information necessary for using the fragment is attached to the fragment that is input and stored in the isolation environment. Unless the authentication is successful, it is not possible to recover the secret information using the fragment or to send the fragment to another isolation environment. Here, the authentication information may be information related to knowledge authentication such as password authentication or challenge-response authentication. Alternatively, the authentication information may be information related to biometric authentication such as facial features. Furthermore, the authentication information may be a condition that authentication by another designated authenticator has been successful. By utilizing authentication by another authenticator in this way, it is possible to reduce the processing load of the authentication process in the isolation environment.

[0058] In this case, in addition to assigning authentication information to all fragments input and stored in the isolation environment, it is also possible to assign authentication information to only some of them. This can be decided on a case-by-case basis depending on what kind of actions by third parties need to be deterred. For example, if the goal is simply to deter the recovery of confidential information from multiple fragments in the isolation environment, authentication information may be assigned only to some of the fragments necessary for recovery. On the other hand, if the goal is to deter the transmission of multiple fragments in one isolation environment to other isolation environments, it is necessary to assign authentication information to all of the multiple fragments.

[0059] Figure 9(a) shows an example in a smartphone 100A where no authentication information is attached to the fragments input and stored in the secure element unit 106. In this example, no authentication information is attached to the two fragments 1 and 2 input and stored in the secure element unit 106. In this case, an attacker can gain unauthorized access to the secure element unit 106, obtain fragments 1 and 2, and use them to restore confidential information.

[0060] Figure 9(b) shows an example in which authentication information is attached to the fragments input and stored in the secure element unit 106 of a smartphone 100A. In this example, authentication information is attached to the two fragments 1 and 2 input and stored in the secure element unit 106. In this case, even if an attacker gains unauthorized access to the secure element unit 106, authentication will be required to use fragments 1 and 2, making it impossible for the attacker to obtain fragments 1 and 2 and use them to restore confidential information, etc.

[0061] "1-7. Embodiment 6 (Assigning Usage Information to Fragments in an Isolated Environment)" There is a possibility that legitimate users or third parties may access the isolated environment and use the fragments or confidential information for purposes other than their intended use. For example, this could involve transmitting a fragment of confidential information intended for signing to another isolated environment.

[0062] Therefore, in Embodiment 6, information (purpose information) is assigned to the fragments input and stored in the isolation environment to limit the uses of the fragments and the confidential information recovered from them, so that the fragments and the confidential information recovered from them can only be used for purposes permitted by the purpose information.

[0063] The usage information for confidential information includes, for example, signing and fragmentation. Furthermore, the usage information for fragmentation may include parameters used during fragmentation (n, t, and s), permission information for sending the fragmented fragments to other isolation environments (such as the destination), permission information for retrieving the fragmented fragments externally, and authentication information for the fragmented fragments. The usage information for the fragments includes permission information for restoring the confidential information, permission information for sending the fragments to other isolation environments (such as the destination), and permission information for retrieving them externally. If fragments used to restore confidential information are assigned different usage information, they can only be used for the purposes permitted by the usage information of all those fragments.

[0064] In this case, in addition to assigning usage information to all fragments input and stored in the isolated environment, it is also possible to assign usage information to only some of them. This can be decided on a case-by-case basis depending on what use each fragment is restricted to.

[0065] Figure 10(a) shows an example in a smartphone 100A where no usage information is attached to the fragments input and stored in the secure element unit 106. In this example, no usage information is attached to the two fragments 1 and 2 input and stored in the secure element unit 106. In this case, an attacker can illegally access the secure element unit 106, obtain fragments 1 and 2, and use them for various purposes.

[0066] Figure 10(b) shows an example in a smartphone 100A where fragments input to and stored in the secure element unit 106 are assigned usage information. In this example, two fragments, Fragment 1 and Fragment 2, input to and stored in the secure element unit 106 are assigned usage information. Fragment 1 is assigned usage information that limits its use to transmission to the cloud. Fragment 2 is assigned usage information that limits its use to the restoration and signing of confidential information. In this case, even if an attacker who has illegally accessed the secure element unit 106 tries to move Fragment 1 to another device (smartphone), etc., it will be impossible to do so because the uses are different. Similarly, even if an attacker who has illegally accessed the secure element unit 106 tries to use Fragment 2 for restoration other than signing, it will be impossible to do so because the uses are different.

[0067] "1-8. Examples of Application of This Technology" Examples of application of this technology will be explained. Figures 11(a) and (b) schematically show examples of application of this technology. Figure 11(a) shows an example in which a signature key as confidential information for accessing an individual's crypto assets is stored in the secure element section 106 of a smartphone 100A as a mobile device. Figure 11(b) shows an example in which a signature key as confidential information for identity verification is stored in the secure element section 106 of a smartphone 100A as a mobile device. Note that examples of application of this technology are not limited to these two.

[0068] The specific operational example of the application to the cryptocurrency signing key shown in Figure 11(a) above will be explained below.

[0069] Refer to Figure 12 to explain Procedure 1 (Generating the Signature Key and Splitting it into Fragments). In Procedure 1, the secure element unit 106 of the smartphone (smartphone A) 100A generates a signature key and splits it into three fragments: Fragment 1, Fragment 2, and Fragment 3. During this splitting, authentication information is assigned to each fragment, and the use of each fragment is further restricted as follows: Fragment 1: A fragment to be moved to the cloud. Fragment 2: A fragment to be restored to a signature key and used for signing. Fragment 3: A fragment to be backed up to another smartphone (another smartphone), which can only be used for "restore + sign" on the other smartphone.

[0070] In this first step, the signing key is split in the secure element unit 106, so even an attacker cannot know the signing key (applied to Embodiment 4). Furthermore, since the use of each fragment is restricted, even if a fragment is illegally obtained from the secure element unit 106, it cannot be used for purposes that do not match the intended purpose. Also, since authentication is required to use each fragment, it cannot be used without the authentication key (applied to Embodiments 5 and 6).

[0071] Refer to Figure 13 to explain Step 2 (moving fragments). In Step 2, the fragments are moved as follows. Note that an encrypted communication channel is used when moving the fragments. Fragment 1: Moves from the secure element section 106 of smartphone (smartphone A) 100A to the cloud 300. Fragment 2: Held by the secure element section 106 of smartphone (smartphone A) 100A. Fragment 3: Moves from the secure element section 106 of smartphone (smartphone A) 100A to the secure element section 106 of smartphone (smartphone B) 100B.

[0072] In this second step, since an encrypted communication channel is used when moving the fragment, the attacker cannot obtain the fragment (applied to Embodiment 3).

[0073] Figure 14 shows an example of the sequence related to steps 1 and 2 described above. (1) The application unit of the smartphone 100A sends a request to the secure element unit 106 to generate a signature key fragment. (2) Next, the secure element unit 106 of the smartphone 100A generates a signature key. (3) Next, the secure element unit 106 of the smartphone 100A creates three fragments (fragment 1, fragment 2, fragment 3) from the signature key and deletes the original signature key. (4) Next, the secure element unit 106 of the smartphone 100A sends a response to the application unit indicating that the generation is complete.

[0074] (5) Next, the application unit of the smartphone 100A sends a request to the secure element unit 106 to retrieve fragment 1. (6) Next, the secure element unit 106 of the smartphone 100A sends fragment 1 to the application unit. (7) Next, the application unit of the smartphone 100A sends fragment 1 to the cloud 300. (8) Next, the cloud 300 reports completion to the application unit of the smartphone 100A. (9) Next, the application unit of the smartphone 100A reports completion to the secure element unit 106. (10) Next, the secure element unit 106 of the smartphone 100A checks the output of fragment 1 and deletes fragment 1. As a result, the secure element unit 106 of the smartphone 100A retains fragments 2 and 3.

[0075] (11) Next, the application unit of smartphone 100A sends a request to the secure element unit 106 to obtain fragment 3. (12) Next, the secure element unit 106 of smartphone 100A sends fragment 3 to the application unit. (13) Next, the application unit of smartphone 100A sends fragment 3 to the application unit of smartphone 100B. (14) Next, the application unit of smartphone 100B sends fragment 3 to the secure element unit 106.

[0076] (15) Next, the secure element unit 106 of smartphone 100B reports completion to the application unit. (16) Next, the application unit of smartphone 100B reports completion to the application unit of smartphone 100A. (17) Next, the application unit of smartphone 100A reports completion to the secure element unit 106. (18) Next, the secure element unit 106 of smartphone 100A checks the output of fragment 3 and deletes fragment 3. As a result, the secure element unit 106 of smartphone 100A retains only fragment 2.

[0077] Refer to Figure 15 to explain step 3 (use of the signing key). In step 3, the secure element unit 106 of the smartphone 100A temporarily obtains fragment 1 from the cloud 300, recovers the signing key from fragment 1 and the fragment 2 it holds, and signs the message. In this case, the signature is generated by encrypting the hash value obtained from the message using the signing key.

[0078] In step 3, the signature key is restored by the secure element unit 106, so the attacker cannot obtain the signature key (applies to Embodiment 1). Also, since fragment 2 is stored in the secure element unit 106, the attacker can only know fragment 1, and therefore cannot restore the signature key (applies to Embodiment 2 (fragment stored in the secure element unit)). Furthermore, since fragment 1 is held in the cloud 300, security is ensured through confidentiality distribution.

[0079] In addition, although the explanation of step 3 above was given using smartphone 100A, if smartphone 100A is lost, the same procedure can be performed on smartphone 100B, in which fragment 3 is held in the secure element section 106.

[0080] Figure 16 shows an example of the sequence related to step 3 described above. (21) The application unit of the smartphone 100A sends a request to the cloud 300 to obtain fragment 1. (22) Next, the cloud 300 sends fragment 1 to the application unit of the smartphone 100A. (23) Next, the application unit of the smartphone 100A sends fragment 1 and the message to the secure element unit 106. (24) Next, the secure element unit 106 of the smartphone 100A recovers the signing key from fragment 1 and fragment 2, (25) and signs the message using this signing key.

[0081] In the above description, we explained an example in which fragment 2 is stored in the secure element section 106 of the smartphone 100A. However, it is also possible to encrypt fragment 2 and manage it outside the secure element section 106. Figure 17 shows procedure 2' (managing the encrypted fragment outside the secure element) in that case.

[0082] Figure 18 shows an example of the sequence related to the above-described procedure 2'. (31) The application unit of the smartphone 100A requests the secure element unit 106 to obtain the encrypted fragment 2. (32) Next, the secure element unit 106 of the smartphone 100A encrypts fragment 2 with the key and deletes fragment 2. (33) Next, the secure element unit 106 of the smartphone 100A sends the encrypted fragment 2 to the application unit as a response.

[0083] Referring to Figure 19, we will now explain step 3' (use of the signing key) when the application unit holds the encrypted fragment 2 in step 2' described above. In step 3', the secure element unit 106 of the smartphone 100A temporarily obtains fragment 1 from the cloud 300, then obtains and decrypts the encrypted fragment 2 from the application unit, recovers the signing key from fragments 1 and 2, and signs the data.

[0084] In this step 3', the signature key is restored by the secure element unit 106, so the attacker cannot obtain the signature key (applied to Embodiment 1). Furthermore, the secure element unit 106 obtains and decrypts the encrypted fragment 2 from the application unit, and the attacker can only know fragment 1, so the signature key cannot be restored (applied to Embodiment 2 (encryption of input fragment)).

[0085] Figure 20 shows an example of the sequence related to step 3' described above. (41) The application unit of the smartphone 100A sends a request to the cloud 300 to obtain fragment 1. (42) Next, the cloud 300 sends fragment 1 to the application unit of the smartphone 100A. (43) Next, the application unit of the smartphone 100A sends the encrypted fragment 2, fragment 1, and the message to the secure element unit 106. (44) Next, the secure element unit 106 of the smartphone 100A decrypts the encrypted fragment 2 with the key. (45) Next, the secure element unit 106 of the smartphone 100A recovers the signing key from fragment 1 and fragment 2, (46) and signs the message using this signing key.

[0086] <2. Modifications> In the embodiments described above, an example is given where the confidential information is a signing key, but the confidential information to which this technology can be applied is not limited to signing keys.

[0087] Furthermore, while preferred embodiments of this disclosure have been described in detail with reference to the accompanying drawings, the technical scope of this disclosure is not limited to such examples. It is clear to any person with ordinary skill in the art of this disclosure that various modifications or alterations may be conceived within the scope of the technical idea set forth in the claims, and these too will naturally fall within the technical scope of this disclosure.

[0088] Furthermore, the effects described herein are merely descriptive or illustrative and not limiting. In other words, the technology relating to this disclosure may produce other effects that are obvious to those skilled in the art from the description herein, in addition to or instead of the effects described herein.

[0089] Furthermore, this technology can also take the following configurations: (1) An information processing device equipped with an isolation environment for restoring confidential information from multiple fragments or for dividing confidential information into multiple fragments. (2) The information processing device according to (1), wherein, when restoring confidential information from the multiple fragments, the isolation environment uses the fragments stored in the isolation environment and the fragments input to the isolation environment from the outside. (3) The information processing device according to (2), wherein the confidential information is divided into n fragments, the confidential information can be restored by collecting at least t fragments, and when the number of fragments stored in the isolation environment is s, s > n - t. (4) The information processing device according to (3), wherein when the number of fragments input to the isolation environment from the outside is r, s + r ≥ t. (5) The information processing device according to (1), wherein, when restoring confidential information from the multiple fragments, the isolation environment uses the multiple fragments input to the isolation environment from the outside. (6) The information processing device according to (5), wherein at least a portion of the multiple fragments input to the isolation environment from the outside are encrypted, and the isolation environment decrypts and uses the encrypted fragments. (7) When dividing the confidential information into multiple fragments, the isolation environment is the information processing device described in (1) above which further generates the confidential information. (8) When restoring the confidential information from the multiple fragments, the isolation environment is the information processing device described in (1) above which further utilizes the confidential information. (9) The isolation environment is the information processing device described in (1) above which sends a portion of the multiple fragments obtained by dividing the confidential information to an external device via an encrypted communication channel or encrypted. (10) The external device is the information processing device described in (9) above which includes an isolation environment or a cloud. (11) The isolation environment is the information processing device described in any of (1) to (10) above which includes a secure element unit or a TEE unit. (12) The confidential information is the information processing device described in (1) to (11) above which is a signing key. (13) An information processing method in which the restoration of confidential information from multiple fragments or the division of confidential information into multiple fragments is performed in an isolation environment.(14) An information processing device comprising an isolation environment for storing a plurality of fragments obtained by partitioning confidential information, wherein the isolation environment transmits at least a portion of the plurality of fragments to an external device via an encrypted communication channel or encrypted. (15) The information processing device according to (14), wherein the isolation environment deletes the fragments transmitted to the external device from the isolation environment. (16) The information processing device according to (14) or (15), wherein the external device is a device equipped with an isolation environment or a cloud. (17) The information processing device according to any one of (14) to (16), wherein the isolation environment includes a secure element unit or a TEE unit. (18) An information processing device comprising an isolation environment for storing a plurality of fragments obtained by partitioning confidential information, wherein the isolation environment assigns authentication information to at least a portion of the plurality of fragments. (19) An information processing device comprising an isolation environment for storing a plurality of fragments obtained by partitioning confidential information, wherein the isolation environment assigns usage information to at least a portion of the plurality of fragments. (20) The information processing device according to (18) or (19), wherein the isolation environment includes a secure element unit or a TEE unit.

[0090] 100... Information terminal 100A, 100B... Smartphone 101... Control unit 102... Storage unit 103... Memory unit 104... Input unit 105... Output unit 106... Secure element unit 107... NFC (Near Field Communication) communication unit 108... Network communication unit 109... TEE (Trusted Execution Environment) unit 200... Another device 300... Cloud

Claims

1. An information processing device equipped with an isolation environment for recovering confidential information from multiple fragments, or for dividing confidential information into multiple fragments.

2. When recovering confidential information from the plurality of fragments, the information processing apparatus according to claim 1, wherein the isolation environment uses fragments stored in the isolation environment and fragments input to the isolation environment from an external source.

3. The information processing apparatus according to claim 2, wherein the secret information is divided into n fragments, the secret information can be restored by collecting at least t fragments, and when the number of fragments stored in the isolation environment is s, s > n - t.

4. The information processing apparatus according to claim 3, wherein s + r ≥ t, when the number of fragments input from the outside to the isolated environment is r.

5. The information processing apparatus according to claim 1, wherein, when recovering confidential information from the plurality of fragments, the isolation environment uses the plurality of fragments input to the isolation environment from an external source.

6. The information processing apparatus according to claim 5, wherein at least a portion of a plurality of fragments input to the isolated environment from the outside is encrypted, and the isolated environment decrypts and uses the encrypted fragments.

7. When dividing the confidential information into multiple fragments, the isolation environment further generates the confidential information, as described in claim 1.

8. The information processing apparatus according to claim 1, wherein, when recovering confidential information from the plurality of fragments, the isolation environment further utilizes the confidential information.

9. The information processing apparatus according to claim 1, wherein the isolation environment sends a portion of the multiple fragments obtained by the division of the secret information to an external device via an encrypted communication channel or after encryption.

10. The information processing apparatus according to claim 9, wherein the external device includes a device or cloud that provides an isolated environment.

11. The information processing apparatus according to claim 1, wherein the isolation environment includes a secure element section or a TEE section.

12. An information processing method for restoring confidential information from multiple fragments, or for dividing confidential information into multiple fragments, in an isolated environment.

13. An information processing device comprising an isolation environment for storing multiple fragments obtained by partitioning confidential information, wherein the isolation environment transmits at least a portion of the multiple fragments to an external device via an encrypted communication channel or in an encrypted state.

14. The information processing apparatus according to claim 13, wherein the isolation environment erases the fragment transmitted to the external device from the isolation environment.

15. The information processing apparatus according to claim 13, wherein the external device includes a device or cloud that provides an isolated environment.

16. The information processing apparatus according to claim 13, wherein the isolation environment includes a secure element section or a TEE section.

17. An information processing device comprising an isolation environment for storing multiple fragments obtained by partitioning confidential information, wherein the isolation environment assigns authentication information to at least a portion of the multiple fragments.

18. An information processing device comprising an isolation environment for storing multiple fragments obtained by partitioning confidential information, wherein the isolation environment assigns usage information to at least a portion of the multiple fragments.

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