SECRET KEY TYPE ELECTRONIC SIGNATURE DEVICE
Patent Information
- Application Number
- VN1202605100
- Authority / Receiving Office
- VN · VN
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2020-12-01
- Publication Date
- 2026-08-17
AI Technical Summary
Current currency management systems lack robust security measures to detect and recover fraudulent changes in transaction, account, and currency information, particularly when illegal alterations occur across multiple devices.
A currency management system comprising transaction, account, and currency information management devices that store and verify transaction information across multiple devices, utilizing electronic signatures to ensure data integrity and facilitate recovery from fraudulent changes, with the option to use public or private key cryptography for secure operations.
The system provides excellent security by enabling detection and recovery of fraudulent changes across devices, ensuring that transaction, account, and currency information remain accurate and secure, even if alterations occur, through the use of electronic signatures and multi-device verification.
Smart Images
Figure VN1202605100_0
Abstract
Description
Currency management system and electronic signature device
[0001] The present invention relates to currency management and electronic signatures.
[0002] A system for managing currency has been proposed (see Patent Document 1).
[0003] Patent No. 6316530
[0004] An object of one embodiment of the present invention is to provide a highly secure currency management system that includes legal tender as a managed object.
[0005] The present invention includes the following embodiment.
[0006] A currency management system comprising a transaction information management device, an account information management device, and a currency information management device, wherein the transaction information management device receives first transaction information from a user terminal, the account information management device receives second transaction information from the transaction information management device, the transaction information management device receives third transaction information from the account information management device, the currency information management device receives fourth transaction information from the transaction information management device, the transaction information management device receives fifth transaction information from the currency information management device, the transaction information management device transmits sixth transaction information to the user terminal, the transaction information management device stores the first to sixth transaction information within its own device, the account information management device receives the first to sixth transaction information from the transaction information management device and stores them within its own device, and the currency information management device receives the first to sixth transaction information from the transaction information management device and stores them within its own device.
[0007] According to one embodiment of the present invention, it is possible to provide a highly secure currency management system that includes legal tender as a management target.
[0008] FIG. 1 is a diagram illustrating an example of the configuration of a currency management system according to embodiment 1. FIG. 2 is a diagram illustrating an example of transaction information. FIG. 3 is a diagram illustrating an example of account information. FIG. 4 is a diagram illustrating an example of currency information. FIG. 5 is a diagram illustrating an example of the operation of the currency management system according to embodiment 1. FIG. 6 is a diagram illustrating how transaction information is stored. FIG. 7 is a diagram illustrating how account information is updated. FIG. 8 is a diagram illustrating how currency information is updated. FIG. 9 is a diagram illustrating an example of the configuration of a currency management system according to embodiment 2. FIG. 10 is a diagram illustrating an example of transaction information to which a digital signature has been attached. FIG. 11 is a diagram illustrating an example of transaction information in embodiment 3. FIG. 12 is a diagram illustrating an example of account information to which a digital signature has been attached. FIG. 13 is a diagram illustrating an example of currency information to which a digital signature has been attached. FIG. 14 is a diagram illustrating an example of the configuration of an electronic signature device.
[0009] [Currency Management System 100 According to Embodiment 1] Fig. 1A is a diagram showing an example of the configuration of a currency management system 100 according to embodiment 1. As shown in Fig. 1A, the currency management system 100 according to embodiment 1 includes a transaction information management device 110, an account information management device 120, and a currency information management device 130.
[0010] (Currency Management System 100) The currency management system 100 is a system for managing currency. In this embodiment, currency is managed by assigning a currency number to every currency. The type of currency is not limited. Currency may be legal tender or non-legal tender. Currency may be encrypted or non-encrypted currency. Currency may be managed by a nation, or may be managed by a specific organization or company. Examples of currency include points and regional promotion coupons.
[0011] (Currency Remittance) Currency management includes currency remittance. In this embodiment, currency remittance is performed by changing account information B and currency information C. In this specification, the requests and responses generated when changing account information B and currency information C are referred to as transactions, and the history of these transactions is referred to as transaction information A. Transaction information A can also be said to be the history of requests and responses generated when changing account information B and currency information C.
[0012] (Transaction Information Management Device 110) The transaction information management device 110 is a device that manages transaction information A. An example of the transaction information management device 110 includes a server device.
[0013] (Transaction Information A) Using transaction information A, it is possible to trace the correct change history of account information B and currency information C, thereby detecting unauthorized changes to account information B and currency information C and restoring the unauthorized changes to the correct information. However, conversely, it is not possible to use account information B and currency information C to detect unauthorized changes to transaction information A and restore the unauthorized changes to the correct information. Therefore, in this embodiment, transaction information A is stored not only in transaction information management device 110, but also in account information management device 120 and currency information management device 130. In this way, even if transaction information A stored in one of transaction information management device 110, account information management device 120, and currency information management device 130 is unauthorizedly altered, the unauthorized change can be detected and the unauthorized changes to the correct information can be restored by using transaction information A stored in the remaining two devices. For example, if transaction information A in the transaction information management device 110 is fraudulently changed, transaction information A in the account information management device 120 and transaction information A in the currency information management device 130 can be used to restore the transaction information A in the transaction information management device 110 to its correct content. Therefore, according to this embodiment, even if any of transaction information A, account information B, and currency information C is fraudulently changed, the fraud can be discovered and the fraudulently changed information can be restored to its correct content. For example, if account information B in the account information management device 120 is fraudulently changed, the fraudulently changed account information B can be restored to its correct content using one or more of the transaction information A stored in the transaction information management device 110, the account information management device 120, and the currency information management device 130, respectively.Furthermore, as described above, for example, if transaction information A in the transaction information management device 110 is fraudulently altered, transaction information A in the transaction information management device 110 can be restored to its correct content using transaction information A in the account information management device 120 and transaction information A in the currency information management device 130. Furthermore, for example, if transaction information A in the transaction information management device 110 and currency information C in the currency information management device 130 are fraudulently altered, transaction information A in the transaction information management device 110 can be restored to its correct content using transaction information A in the account information management device 120 and transaction information A in the currency information management device 130, and currency information C in the currency information management device 130 can be restored to its correct content using one or more of transaction information A in the account information management device 120 and transaction information A in the currency information management device 130 (or further, transaction information A in the transaction information management device 110 that has been recovered to its correct content). Thus, according to this embodiment, it is possible to provide a highly secure currency management system 100 that includes legal tender as a managed object.
[0014] FIG. 1B is a diagram showing an example of transaction information A. As shown in FIG. 1B, transaction information A includes, for example, a transaction number, transaction type, remittance source account number, remittance destination account number, remittance amount, and date and time. This information can be stored in correspondence with each other, for example, in table format. Specifically, this information can be stored in different columns of the same row of the table. This information is merely an example, and transaction information A may include information other than the above. Furthermore, the remittance source account number, remittance destination account number, and remittance amount may not be included in transaction information A. As described above, according to this embodiment, this information is stored in the transaction information management device 110, the account information management device 120, and the currency information management device 130, respectively.
[0015] <Transaction Number> The transaction number is a number that identifies a transaction. Examples of transaction numbers include a number sequence or a character string.
[0016] <Transaction Type> The transaction type is a number that identifies the type of transaction. Examples of transaction types include a remittance request, an account information confirmation request, an account information confirmation response, a currency information confirmation request, a currency information confirmation response, and a remittance response.
[0017] <Remitter's Account Number> The remitter's account number is a number that identifies the remitter's account number. Examples of the remitter's account number include a numeric sequence or a character string. When a digital signature is added to transaction information and a private key cryptosystem is used to add or verify the digital signature (when the cryptographic keys of the users or devices are shared between each device), the remitter's account number is preferably information that can identify the cryptographic key of the remitter (e.g., a key number). Furthermore, when a digital signature is added to transaction information and a public key cryptosystem is used to add or verify the digital signature, the remitter's account number is preferably information that can identify the public key of the remitter's user.
[0018] <Recipient Account Number> The recipient account number is a number that identifies the recipient's account number. Examples of recipient account numbers include a numeric string or a character string. As with the sender account number, the recipient account number is preferably information that can identify the encryption key of the recipient user (e.g., key number) or information that can identify the recipient user's public key.
[0019] <Remittance Amount> The remittance amount is information that specifies the amount to be remitted. An example of the remittance amount is a sequence of numbers.
[0020] <Date and Time> The date and time is the date and time when the transaction occurred. For example, the date and time is the time when transaction information A was sent.
[0021] (Account information management device 120) The account information management device 120 is a device that manages account information B. An example of the account information management device 120 is a server device. The account information management device 120 is connected to the transaction information management device 110, for example, via a network. Examples of a network include the Internet and an intranet.
[0022] (Account Information B) Account information B is information that specifies the relationship between an account and a balance.
[0023] FIG. 1C is a diagram showing an example of account information B. As shown in FIG. 1C, account information B includes an account number, a balance, and the last update date and time. This information can be stored in correspondence with each other, for example, in a table format. Specifically, this information can be stored in different columns of the same row of the table. This information is an example, and account information B may include information other than the above information.
[0024] <Account Number> The account number is a number that identifies an account. Examples of account numbers include a sequence of numbers and a character string.
[0025] <Balance> A balance is information that specifies the amount of currency held in an account. An example of a balance includes a sequence of numbers.
[0026] <Last Updated Date and Time> The last updated date and time is the date and time when the account information B was last updated.
[0027] (Currency information management device 130) The currency information management device 130 is a device that manages currency information C. An example of the currency information management device 130 includes, for example, a server device. The currency information management device 130 is connected to the transaction information management device 110, for example, via a network. The currency information management device 130 may or may not be connected to the account information management device 120, for example, via a network. Examples of a network include the Internet and an intranet.
[0028] (Currency Information C) Currency information C refers to information for managing currency.
[0029] FIG. 1D is a diagram showing an example of currency information C. As shown in FIG. 1D, currency information C includes a currency number, a currency type, a currency value, an account number, and a last update date and time. This information can be stored in correspondence with each other, for example, in a table format. Specifically, this information can be stored in different columns of the same row of a table. This information is an example, and currency information C may include information other than the above information. Furthermore, currency value does not have to be included in currency information C.
[0030] <Currency Number> The currency number is a number that identifies a currency. As described above, in this embodiment, a currency number is assigned to every currency.
[0031] <Currency Type> The currency type is information that identifies the type of currency. Examples of currency types include Japanese yen, US dollars, euros, Chinese yuan, and points that have exchange value in specific regions or companies. Note that when only one type of currency is managed, the currency type does not need to be included in the currency information. Furthermore, when the currency number is information that can identify the currency type (for example, when information that identifies the currency type (yen) is included at the beginning or end of the currency number as part of the currency number, such as "yen1111" or "1111 yen"), the currency type does not need to be included in the currency information.
[0032] <Currency Value> Currency value is information that specifies the value of a currency. For example, assume that two currencies are issued, with the first currency assigned currency number 1 and the second currency assigned currency number 2. In this case, if Japanese yen is stored as the currency type and 500 as the currency value in association with currency number 1, the currency with currency number 1 is worth 500 yen. Furthermore, if US dollars are stored as the currency type and 100 as the currency value in association with currency number 2, the currency with currency number 2 is worth 100 US dollars.
[0033] <Account Number> The account number is the account number of the user who holds the currency identified by the currency number. Examples of account numbers include a number sequence and a character string.
[0034] <Last Update Date and Time> The last update date and time is the date and time when the currency information C was last updated.
[0035] (User terminals 210, 220) A plurality of user terminals 210, 220 are connected to the transaction information management device 110, for example, via a network. Examples of the user terminals 210, 220 include smartphones, laptop computers, and desktop computers. Examples of the network include the Internet and an intranet.
[0036] The transaction information management device 110 functions as an interface for the user terminals 210, 220. The account information management device 120 and the currency information management device 130 cannot send or receive data to or from the user terminals 210, 220 without going through the transaction information management device 110. Requests from the user terminals 210, 220 are received by the transaction information management device 110. The transaction information management device 110 sends requests to the account information management device 120 and the currency information management device 130 based on requests from the user terminals 210, 220. In addition, responses from the account information management device 120 and the currency information management device 130 are received by the transaction information management device 110. Then, based on these responses, the transaction information management device 110 sends responses to the user terminals 210, 220.
[0037] (Example of operation of the currency management system 100 according to embodiment 1) Figure 1E is a diagram showing an example of operation of the currency management system 100 according to embodiment 1. Below, an example of operation of the currency management system 100 according to embodiment 1 will be described with reference to Figure 1E. In the following example, it is assumed that the account number held by the user of the user terminal 210 is 1, the account number held by the user of the user terminal 210 is 2, and 500 yen is transferred from the account with account number 1 to the account with account number 2 in response to a transfer request from the user terminal 210.
[0038] (Step S101) First, the transaction information management device 110 receives first transaction information a1 from the user terminal 210. The first transaction information a1 is an example of transaction information A. Examples of first transaction information a1 include a remittance request and an account issuance request. In this embodiment, the first transaction information a1 is assumed to be a remittance request.
[0039] (Step S102) Next, the account information management device 120 receives second transaction information A from the transaction information management device 110. Second transaction information a2 is an example of transaction information A. Examples of second transaction information a2 include an account information update request and an account information confirmation request. If the second transaction information a2 is an account information update request, the account information management device 120 updates the account information B after receiving the second transaction information a2. As a result, the account information B stored in the account information management device 120 changes, for example, from the pre-update state to the post-update state shown in FIG. 1G. Furthermore, if the second transaction information a2 is an account information confirmation request, the account information management device 120 checks the account information B after receiving the second transaction information a2, and confirms, for example, whether the account holds a balance equal to or greater than the remittance amount.
[0040] (Step S103) Next, transaction information management device 110 receives third transaction information a3 from account information management device 120. Third transaction information a3 is an example of transaction information A. Examples of third transaction information a3 include, for example, an account information update response and an account information confirmation response. The account information update response is, for example, a response indicating whether the account information has been updated successfully. The account information confirmation response is, for example, a response indicating the confirmation result of whether the account has a balance equal to or greater than the remittance amount.
[0041] (Step S104) Next, the currency information management device 130 receives fourth transaction information a4 from the transaction information management device 110. The fourth transaction information a4 is an example of transaction information A. The fourth transaction information a4 is, for example, a currency information update request or a currency information confirmation request. If the fourth transaction information a4 is a currency information update request, the currency information management device 130 updates the currency information C after receiving the fourth transaction information a4. As a result, the currency information C stored in the currency information management device 130 changes, for example, from the pre-update state to the post-update state shown in FIG. 1H. Furthermore, if the fourth transaction information a4 is a currency information confirmation request, the currency information management device 130 checks the currency information C after receiving the fourth transaction information a4, and checks, for example, whether a currency exists that is associated with the account number of the remitter's user.
[0042] (Step S105) Next, the transaction information management device 110 receives fifth transaction information a5 from the currency information management device 130. The fifth transaction information a5 is an example of transaction information A. Examples of fifth transaction information a5 include a currency information update response and a currency information confirmation response. The currency information update response is, for example, a response indicating whether the currency information has been updated successfully. The currency information confirmation response is, for example, a response indicating the confirmation result of whether a currency exists that is associated with the account number of the remitter's user.
[0043] (Step S106) Next, the transaction information management device 110 sends sixth transaction information a6 to the user terminal 210. The sixth transaction information a6 is an example of transaction information A. Examples of the sixth transaction information a6 include a remittance response and an account issuance response. In this embodiment, the sixth transaction information a6 is a remittance response. The remittance response is, for example, a response indicating whether the remittance was successful.
[0044] (Step S107) Next, the transaction information management device 110 stores the first to sixth transaction information items therein. As a result, the transaction information A stored in the transaction information management device 110 changes, for example, from before storage to after storage as shown in FIG. 1F.
[0045] (Steps S108, S109) Next, account information management device 120 receives the first through sixth transaction information from transaction information management device 110 and stores them internally. As a result, transaction information A stored in account information management device 120 changes, for example, from before storage to after storage as shown in FIG. 1F.
[0046] If, after step S102, account information management device 120 confirms account information B rather than updating it, it updates account information B after receiving the first through sixth transaction information from transaction information management device 110. As a result, account information B stored in account information management device 120 changes, for example, from before the update to after the update as shown in FIG. 1G.
[0047] (Steps S110 and S111) Next, the currency information management device 130 receives the first to sixth transaction information from the transaction information management device 110 and stores them internally. As a result, the transaction information A stored in the currency information management device 130 changes, for example, from before storage to after storage as shown in FIG. 1H.
[0048] If the currency information management device 130 confirms the currency information C rather than updating it after step S104, the currency information management device 130 updates the currency information C after receiving the first to sixth transaction information from the transaction information management device 110. As a result, the currency information C stored in the currency information management device 130 changes, for example, from before the update to after the update as shown in FIG. 1H.
[0049] In this embodiment, the transaction information A is stored in the transaction information management device 110 (step S107), the account information management device 120 (step S108), and the currency information management device 130 (step S110) in that order, but the order in which the transaction information A is stored (the order of steps S107, 108, 110) is not important.
[0050] As described above, using transaction information A makes it possible to trace the correct change history of account information B and currency information C, thereby detecting unauthorized changes to account information B and currency information C and restoring the unauthorized changes to the correct information. However, conversely, it is not possible to use account information B and currency information C to detect unauthorized changes to transaction information A and restore the unauthorized changes to the correct information. Therefore, in this embodiment, transaction information A is stored not only in transaction information management device 110, but also in account information management device 120 and currency information management device 130. In this way, even if transaction information A stored in one of transaction information management device 110, account information management device 120, and currency information management device 130 is unauthorizedly altered, the unauthorized change can be detected and the unauthorized changes to the correct information can be restored by using transaction information A stored in the remaining two devices. For example, if transaction information A in the transaction information management device 110 is fraudulently changed, transaction information A in the account information management device 120 and transaction information A in the currency information management device 130 can be used to restore the transaction information A in the transaction information management device 110 to its correct content. Therefore, according to this embodiment, even if any of transaction information A, account information B, and currency information C is fraudulently changed, the fraud can be discovered and the fraudulently changed information can be restored to its correct content. For example, if account information B in the account information management device 120 is fraudulently changed, the fraudulently changed account information B can be restored to its correct content using one or more of the transaction information A stored in the transaction information management device 110, the account information management device 120, and the currency information management device 130, respectively.Furthermore, as described above, for example, if transaction information A in the transaction information management device 110 is fraudulently altered, transaction information A in the transaction information management device 110 can be restored to its correct content using transaction information A in the account information management device 120 and transaction information A in the currency information management device 130. Furthermore, for example, if transaction information A in the transaction information management device 110 and currency information C in the currency information management device 130 are fraudulently altered, transaction information A in the transaction information management device 110 can be restored to its correct content using transaction information A in the account information management device 120 and transaction information A in the currency information management device 130, and currency information C in the currency information management device 130 can be restored to its correct content using one or more of transaction information A in the account information management device 120 and transaction information A in the currency information management device 130 (or further, transaction information A in the transaction information management device 110 that has been recovered to its correct content). Thus, according to this embodiment, it is possible to provide a highly secure currency management system 100 that includes legal tender as a managed object.
[0051] [Currency Management System 400 According to Embodiment 2] FIG. 2A is a diagram showing an example of the configuration of a currency management system 400 according to embodiment 2. As shown in FIG. 2A, in the currency management system 400 according to embodiment 2, the transaction information management device 110, the account information management device 120, and the currency information management device 130 each include electronic signature devices 310 to 330. Furthermore, the user terminals 210 and 220 also include electronic signature devices 340 and 350, respectively. Embodiment 2 differs from embodiment 1 in that an electronic signature created using these electronic signature devices 310 to 350 is assigned to transaction information A. An example of an electronic signature includes a hash value calculated using a hash function. It is preferable that the electronic signature devices 310 to 350 be tamper-resistant.
[0052] If a digital signature is attached to the transaction information A, verifying the digital signature attached to the transaction information A can detect whether the transaction information A has been tampered with. Therefore, for example, even if the transaction information A in two of the transaction information management device 110, the account information management device 120, and the currency information management device 130 is tampered with, the transaction information A in the remaining device can be used to recover the tampered transaction information A in the two devices. For example, assume that the transaction information A in the transaction information management device 110 and the account information management device 120 is tampered with. In this case, the transaction information management device 110 and the account information management device 120 can detect the tampering by verifying the digital signature attached to each transaction information A. On the other hand, verifying the digital signature attached to the transaction information A stored in the currency information management device 130 can determine that the transaction information A has not been tampered with. Therefore, the transaction information A stored in the currency information management device 130 can be used to recover the transaction information A stored in the transaction information management device 110 and the account information management device 120 to the correct content.
[0053] The digital signature devices 310 to 350 are devices that create and verify digital signatures. There are no particular limitations on the methods for creating and verifying digital signatures. These methods can be performed, for example, using a public key cryptosystem or a private key cryptosystem. In the second embodiment, the public key cryptosystem is used.
[0054] FIG. 2B shows an example of transaction information A to which an electronic signature has been attached. As shown in FIG. 2B , in this embodiment, an electronic signature is attached to each piece of transaction information A. The nth piece of transaction information A is assigned the nth electronic signature, where n is an integer greater than or equal to 1. The electronic signature attached to each piece of transaction information A is created using the encryption key of the device transmitting the transaction information A. For example, the electronic signature attached to the first transaction information a1 described above is created using the encryption key of the user terminal 210. The electronic signatures attached to the second, fourth, and sixth transaction information a2, a4, and a6 are created using the encryption key of the transaction information management device 110. The electronic signature attached to the third transaction information a3 is created using the encryption key of the account information management device 120. The electronic signature attached to the fifth transaction information a5 is created using the encryption key of the currency information management device 130. An example of the encryption key of the user terminal 210 includes the encryption key of the user who operates or owns the user terminal 210. An example of the encryption key of each device includes an encryption key that is owned or assigned for each device by the administrator of this embodiment.
[0055] As described above, according to this embodiment, even if transaction information A in two of the transaction information management device 110, account information management device 120, and currency information management device 130 is fraudulently altered, the fraudulently altered transaction information A in the two devices can be recovered using the transaction information A in the remaining device. Therefore, as long as the transaction information A stored in at least one device is protected with correct content, all information, including account information B and currency information C, can be recovered to the correct content. For example, consider a case where all information other than transaction information A in the transaction information management device 110 is fraudulently altered, that is, where account information B and transaction information A in the account information management device 120, and currency information C and transaction information A in the currency information management device 130 are fraudulently altered. Even in such a case, the electronic signature attached to transaction information A can be used to determine that the transaction information A in the transaction information management device 110 is correct and that the transaction information A in the account information management device 120 and the currency information management device 130 has been fraudulently altered. Therefore, transaction information A in transaction information management device 110 can be used to restore the transaction information A in the remaining two devices to its correct content. Furthermore, transaction information A in transaction information management device 110 (or, further, transaction information A recovered to its correct content in account information management device 120 and currency information management device 130) can be used to discover that account information B in account information management device 120 and currency information C in currency information management device 130 have been fraudulently altered. Then, transaction information A in transaction information management device 110 (or, further, transaction information A recovered to its correct content in account information management device 120 and currency information management device 130) can be used to restore account information B in account information management device 120 and currency information C in currency information management device 130 to their correct content.
[0056] [Currency Management System of Embodiment 3] The currency management system of embodiment 3 differs from the currency management system 100 of embodiment 2 in that the nth electronic signature is created using the nth transaction information A and the (n-1)th electronic signature. The currency management system of embodiment 3 also differs from the currency management system of embodiment 2 in that the nth electronic signature attached to the nth transaction information A is verified by comparing the electronic signature created using the nth transaction information A and the (n-1)th electronic signature with the nth electronic signature. Here, "n-1" means n minus 1, i.e., a number one less than n. In embodiment 3, for example, the third electronic signature attached to the third transaction information a3 can be created using the third transaction information a3 and the second electronic signature. For example, the third electronic signature attached to the third transaction information a3 can be verified by comparing the electronic signature created using the third transaction information a3 and the second electronic signature with the attached third electronic signature.
[0057] According to this embodiment, as shown in FIG. 3 , the fourth electronic signature (#3) is created using the fourth transaction information a4 (#1) and the third electronic signature (#2). For example, the fourth electronic signature (#3) can be created by performing a predetermined calculation using the fourth transaction information a4 (#1), the third electronic signature (#2), and the encryption key of the transaction information management device 110. Furthermore, the fourth electronic signature (#3) can be verified using the fourth transaction information a4 (#1) and the third electronic signature (#2). For example, a verification electronic signature can be created by performing a predetermined calculation using the fourth transaction information (#1), the third electronic signature (#2), and the encryption key of the transaction information management device 110. If this verification electronic signature matches the fourth electronic signature (#3) attached to the fourth transaction information a4, it can be determined that the fourth transaction information a4 has a valid electronic signature. An example of the predetermined calculation is calculation using a hash function.
[0058] The 0th digital signature is a value that is predetermined as an initial value.
[0059] According to this embodiment, to change the n-th digital signature, the (n-1)-th digital signature must be changed, and to change the n-1-th digital signature, the (n-2)-th digital signature must be changed. This relationship continues up to the first digital signature, so the n-th digital signature cannot be changed unless the first digital signature is changed. Therefore, the possibility of fraudulent changes to transaction information A can be reduced.
[0060] In this embodiment, the (n-1)th electronic signature is required to verify the nth electronic signature. Therefore, in the example shown in FIG. 1E, it is preferable to transmit information that can identify the first electronic signature, such as the first transaction information a1 to which the first electronic signature is attached, along with the second transaction information a2. This allows the account information management unit 120 to quickly use the first electronic signature required to verify the second electronic signature.
[0061] Similarly, in this embodiment, it is preferable that information that can identify the third electronic signature, such as the third transaction information a3 to which the third electronic signature is attached, be transmitted together with the fourth transaction information a4, so that the currency information management device 130 can quickly use the third electronic signature required to verify the fourth electronic signature.
[0062] Similarly, in this embodiment, it is preferable that information that can identify the fifth digital signature, such as the fifth digital signature-affixed fifth transaction information a5, be transmitted together with the sixth transaction information a6, so that the user terminal 210 can quickly use the fifth digital signature required to verify the sixth digital signature.
[0063] Note that the zeroth digital signature is required to verify the first digital signature, but the zeroth digital signature is an initial value. Therefore, if the transaction information management device 110 stores this digital signature in advance, the transaction information management device 110 can quickly use the zeroth digital signature required to verify the first digital signature, even if information that can identify the zeroth digital signature is not transmitted along with the first transaction information.
[0064] Furthermore, the second electronic signature is required to verify the third electronic signature, and the second signature is an electronic signature assigned by the transaction information management device 110. Therefore, if the transaction information management device 110 stores the second electronic signature internally after creating it, the transaction information management device 110 can quickly use the second electronic signature required to verify the third electronic signature even if information that can identify the second electronic signature (e.g., second transaction information a2) is not sent along with the third transaction information.
[0065] Furthermore, the fourth electronic signature is required to verify the fifth electronic signature, and the fourth signature is an electronic signature assigned by the transaction information management device 110. Therefore, if the transaction information management device 110 stores the fourth electronic signature internally after creating it, the transaction information management device 110 can quickly use the fourth electronic signature required to verify the fifth electronic signature even if information that can identify the fourth electronic signature (e.g., fourth transaction information a4) is not transmitted along with the fifth transaction information.
[0066] [Currency Management System According to Fourth Embodiment] Figure 4 is a diagram showing an example of account information B to which a digital signature has been attached. As shown in Figure 4, the currency management system according to the fourth embodiment differs from the currency management system 100 according to the first embodiment in that a digital signature is attached to account information B. The digital signature attached to account information B can be created using the account information B to which the digital signature is attached and an encryption key of the account information management device 120. For example, in the case of account information B identified by account number 2, a predetermined calculation can be performed using the account information B identified by account number 2 and the encryption key of the account information management device 120 to calculate the digital signature to be attached to account information B identified by account number 2. An example of the predetermined calculation includes a calculation using a hash function.
[0067] As described above, fraudulent activity against account information B can be detected and recovered using transaction information A. However, when using transaction information A to detect fraud, it is necessary to trace back transaction information A and check the change history of account information B from the beginning. For example, if there are 100 pieces of transaction information, it is necessary to trace back transaction information A in order, starting from the first transaction information, to determine whether account information B has been correctly changed. Therefore, when a large number of transactions are accumulated, such as after multiple currency transfers, determining whether account information B has been fraudulently changed may require a huge amount of processing, which may delay the detection of fraud. Furthermore, if such a large amount of processing is required to detect fraud, it becomes difficult to frequently execute fraud detection processing for account information B using transaction information A. Therefore, in this embodiment, an electronic signature is attached to account information B. In this way, by verifying the electronic signature attached to account information B, it is possible to detect whether account information B has been fraudulently changed without using transaction information A, thereby enabling early detection of fraudulent changes to account information B. After the fraud is discovered, the transaction information A can be used to restore the account information B to its correct contents.
[0068] [Currency Management System According to Embodiment 5] Figure 5 is a diagram showing an example of currency information C to which an electronic signature is attached. As shown in Figure 5, the currency management system according to embodiment 5 differs from the currency management system 100 according to embodiment 1 in that an electronic signature is attached to the currency information C. The electronic signature attached to the currency information C can be created using the currency information C to which the electronic signature is attached and an encryption key of the currency information management device 130. For example, in the case of currency information C identified by currency number 3, a predetermined calculation can be performed using the currency information C identified by currency number 3 and the encryption key of the currency information management device 130 to calculate the electronic signature to be attached to the currency information C identified by currency number 3. An example of the predetermined calculation includes calculation using a hash function.
[0069] According to this embodiment, as in the case of attaching a digital signature to account information B described in embodiment 4, it is possible to detect fraud in currency information C early on without using transaction information A. If fraud is detected in currency information C, it is possible to use transaction information A to restore currency information C to its correct content.
[0070] [Currency Management System According to Embodiment 6] FIG. 6 is a diagram illustrating an example of the configuration of the electronic signature device 310. As shown in FIG. 6, the electronic signature device 310 preferably stores cryptographic keys and authorizations in association with each other, and is capable of executing only the operations corresponding to the authorizations among the operations using the cryptographic keys. The electronic signature devices 320 to 350 can be configured similarly to the electronic signature device 310, except for the content of the authorizations. In Embodiment 2, the electronic signature devices 310 to 350 create and verify electronic signatures based on a public key cryptosystem. However, the public key cryptosystem uses a public key and a private key, and the public key is very long (e.g., 2048 bits). On the other hand, the private key system uses a private key (e.g., 256 bits) for encryption and verification. Therefore, the private key system does not require a long public key, thereby reducing the time required for creating, assigning, and verifying electronic signatures. However, when the private key system is adopted, the cryptographic key (private key) must be shared among multiple electronic signature devices. Therefore, even an electronic signature device that only verifies electronic signatures created with a certain encryption key can still create electronic signatures using that encryption key, posing a security problem. For example, in the above example, the transaction information management device 110 would possess not only its own encryption key, but also the encryption keys of the user terminals 210 and 220, the account information management device 120, and the currency information management device 130. However, in the transaction information management device 110, the encryption keys of the user terminals 210 and 220, the account information management device 120, and the currency information management device 130 are only used to verify electronic signatures. Despite this, the transaction information management device 110 can create electronic signatures using the encryption keys of the user terminals 210 and 220, the account information management device 120, and the currency information management device 130. In other words, the transaction information management device 110 can masquerade as the user terminals 210 and 220, the account information management device 120, and the currency information management device 130. Therefore, in this embodiment, the digital signature devices 310 to 350 employ a secret key system, and an encryption key (secret key) is shared among the multiple digital signature devices 310 to 350 .However, in this embodiment, to avoid security issues, multiple shared encryption keys (private keys) are assigned authorization, and the electronic signature devices 310 to 350 can only use each of the multiple encryption keys (private keys) for processes corresponding to that authorization. This arrangement ensures security while shortening the time required for creating, assigning, and verifying electronic signatures. For example, as shown in FIG. 6 , the electronic signature device 310 of the transaction information management device 110 has not only its own encryption key but also encryption keys for the user terminals 210 and 220, the account information management device 120, and the currency information management device 130. However, it is authorized to assign and verify the encryption key of the transaction information management device 110, and only authorized to verify the encryption keys of the other devices. In this arrangement, the electronic signature device 310 of the transaction information management device 110 can create, assign, and verify electronic signatures using the encryption key of the transaction information management device 110, but can only verify electronic signatures using the encryption keys of the other devices. The electronic signature device described in this embodiment, i.e., an electronic signature device that stores cryptographic keys and authorizations in association with each other and performs only the operations corresponding to the authorizations among the operations using the cryptographic keys (e.g., creating and verifying electronic signatures) (e.g., an electronic signature device in which the authorization stored in association with cryptographic key E is only for verifying electronic signatures can verify electronic signatures using the cryptographic key E, but cannot create electronic signatures using the cryptographic key E. On the other hand, an electronic signature device in which the authorization stored in association with cryptographic key E is for creating and verifying electronic signatures can both create and verify electronic signatures using the cryptographic key E), can be preferably used as the electronic signature devices 310 to 350 provided in the transaction information management device 110, the account information management device 120, the currency information management device 130, and the user terminals 210 and 220. However, the electronic signature device is not limited to use in systems that manage currency, and can be widely used in various devices and systems that employ a private key system other than the devices and systems described above.
[0071] Although the embodiments have been described above, the present invention is not limited to these descriptions in any way.
[0072] 100, 400 Currency management system 110 Transaction information management device 120 Account information management device 130 Currency information management device 210 User terminal 220 User terminal 310 to 350 Digital signature device A Transaction information B Account information C Currency information
Claims
1. A currency management system comprising a transaction information management device, an account information management device, and a currency information management device, wherein the transaction information management device receives first transaction information from a user terminal, the account information management device receives second transaction information from the transaction information management device, the transaction information management device receives third transaction information from the account information management device, the currency information management device receives fourth transaction information from the transaction information management device, the transaction information management device receives fifth transaction information from the currency information management device, the transaction information management device sends sixth transaction information to the user terminal, the transaction information management device stores the first to sixth transaction information within its own device, the account information management device receives the first to sixth transaction information from the transaction information management device and stores them within its own device, and the currency information management device receives the first to sixth transaction information from the transaction information management device and stores them within its own device.
2. The currency management system according to claim 1, wherein the nth transaction information is given the nth digital signature, where n is an integer of 1 or greater.
3. The currency management system according to claim 2, wherein the nth electronic signature is created using the nth transaction information and the (n-1)th electronic signature, with the 0th electronic signature being a predetermined initial value.
4. A currency management system as described in claim 3, in which the nth electronic signature attached to the nth transaction information is verified by comparing the electronic signature created using the nth transaction information and the (n-1)th electronic signature with the nth electronic signature.
5. A currency management system as described in any one of claims 1 to 4, wherein the account information management device stores account information in association with an electronic signature created using the account information and an encryption key of the account information management device.
6. A currency management system as described in any one of claims 1 to 5, wherein the currency information management device stores currency information in association with an electronic signature created using the currency information and an encryption key of the currency information management device.
7. An electronic signature device that stores cryptographic keys and authorizations in association with each other, and that can execute only the processes that correspond to the authorizations among the processes that use the cryptographic keys.