Patent Application
20230252457
The present invention relates to a method for transaction control, a computer-readable recording medium having stored therein transaction control program, and an information processing apparatus.
In recent years, various token economies using blockchains (BCs) have been launched. In addition, a technique of a cross chain that can make transactions across multiple BCs is known. As one form of a cross chain, a connection chain (CC) that connects multiple blockchains with a blockchain exists.
A BC is sometimes operated so that a third party can access a ledger. In such cases, personal privacy-related information “who used what service”, e.g., information regarding a relationship between a remittance source and a remittance destination of a transaction, may be known to a third party.
As a first scheme of concealing the relationship between a remittance source and a remittance destination of a transaction from a third party, in other words, suppressing a transaction of a concealing target from being identified, mixing is known in which multiple transactions are aggregated into a servicer called a tumbler. However, in mixing, since a transaction is caused to wait for undergoing the mixing in a CC serving as a tumbler, execution delay of the transaction may occur.
Further, as a second scheme, a scheme is known which suppresses occurrence of an execution delay of a transaction by recruiting participants to the mixing, not waiting for a transaction for mixing to occur spontaneously as in the first scheme.
For example, related art is disclosed in Japanese Laid-open Patent Publication No. 2019-053712.
As one aspect, a method for transaction control may cause a computer to execute the following process. The process may include performing transaction control including receiving a plurality of transaction generated in a plurality of blockchain networks and transmitting the plurality of transactions to one or more blockchain networks corresponding to respective destinations of the plurality of transactions, and the transaction control may include controlling, based on an execution cost to execute a transaction in each of the plurality of blockchain networks and a blockchain network generating a first transaction having at least one of a transmission source and a transmission destination being a concealing target among the plurality of blockchain networks, a number of second transactions to be generated by each of the plurality of blockchain networks to conceal the first transaction.
The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.
In the second scheme, in order to perform mixing on a first transaction which is a concealing target, a CC will generate a second transaction for concealing the first transaction.
As the above, the second scheme, which generates the second transaction that does not need to be originally generated, may cause an increase in an execution cost for executing the first transaction of concealing target as compared with the first scheme. An example of the execution cost is the cost (commission) for executing transactions in a BC. In addition to or in place of the cost, the execution cost may include a processing load, a network load, and the like of a BC, a CC, or both.
Hereinafter, an embodiment of the present invention will now be described with reference to the drawings. However, the embodiment described below is merely illustrative and there is no intention to exclude the application of various modifications and techniques that are not explicitly described in the embodiment. For example, the present embodiment can be variously modified and implemented without departing from the scope thereof. In the drawings used in the following description, the same reference numerals denote the same or similar parts unless otherwise specified.
In response to a request from the user A, the CC 120 transfers one or more tokens of the user A to the primary account CA 121 (CA #0) of the CC 120 on the BC 110. Then, the CC 120 transfers tokens equivalent to the tokens transferred to the CA 121 to the primary account CA 122 (CA #1) of the CC 120 on the BC 130 and transfers the tokens from the CA 122 to the account of the user B.
In the example of
Here, a BC is sometimes operated so that a third party can access a ledger. Examples of such a circumstance include cases where a public chain is used and cases where a consortium chain is used and a third party is allowed to access a ledger for the purpose of evaluating each other on the basis of the transaction records.
If a third party can access a ledger, personal privacy-related information “who used what service” comes to be known to the third party through a single BC or multiple BCs via a CC.
In the example of
This allows a third party to know information regarding a relationship between a remittance source and a remittance destination of a transaction that indicates that the user A uses the service of the user B, in other words, personal privacy-related information.
In order to solve the inconvenience caused by the first scheme, it is conceivable that the tumbler 123 generates a second transaction for concealing a first transaction of a concealing target, thereby performing mixing of the first transaction by means of the above-described second scheme. However, generating an originally dispensable second transaction, the second scheme may cause an increase in the total execution cost to be generated to execute the first transaction of a concealing target as compared to the first scheme.
As a solution to the above, one embodiment describes, for example, a scheme of reducing the execution cost of one or more transactions additionally generated for the purpose of mixing in a CC connecting multiple BCs in contrast to the second scheme.
Note that, the one embodiment assumes, unlike a transaction on a single BC, a service that performs mixing of transactions across a CC that connects multiple BCs.
The one embodiment further assumes that an execution cost occurs for each transaction, that the transaction execution costs vary among BCs, and that the execution cost of each BC is published. The publication of the execution costs may be obtained, for example, in a CC.
In the following description, a transaction of a concealing target to be executed may sometimes be referred to as a “genuine transaction”. A genuine transaction is an example of the first transaction. An example of a transaction of a concealing target is a transaction that conceals information on the transmitter/receiver, such as the remittance sender/receiver, from a third party. The transmitter/receiver may be, for example, a transmission source or a transmission destination of a transaction, or both, and is an example of the information regarding a relationship between a transmission source and a transmission destination of a transaction. An example of the remittance sender/receiver may be a remittance source or a remittance destination of a transaction, or both.
In the following description, one or more transactions generated by a tumbler by, for example, recruiting participants for the purpose of concealing the transmitter/receiver (remittance sender/receiver) of a genuine transaction may sometimes be referred to as “fake transactions”. A fake transaction is an example of the second transaction. A fake transaction may also be referred to as a “dummy transaction.”
Here, a comparative example for reducing the execution cost of fake transactions, which are originally dispensable, under the above conditions will now be described.
As a first comparative example, a scheme of generating a fake transaction in a BC having the smallest execution cost is conceivable. However, in the first comparative example, all fake transactions are outputted from one BC that runs with the smallest execution cost. For the above, a genuine transaction can be identified by a third party unless the remittance source of the genuine transaction is the remittance sender on the same BC as that of the remittance source of the fake transaction. Consequently, the remittance sender/receiver of the genuine transaction is not concealed to make it difficult to successfully protect the personal privacy-related information on a genuine transaction.
As a second comparative example, a scheme of generating all fake transactions on the same BC as that of the remittance sender of a genuine transaction is conceivable. However, in the second comparative example, the cost of each fake transaction becomes higher as the execution cost of the BC that remits the genuine transaction is higher (cost).
With the above-described disadvantages described in the first and second comparative examples in view, the one embodiment exemplarily describes a method for reducing the execution cost of the second transactions while ensuring concealment of the first transaction by suppressing the first transaction from being uniquely identified.
Each of the BCs 11-1 to 11-6 is an example of a blockchain network in which an execution cost is generated for each transaction, and the execution costs thereof are assumed to be published. In addition, the execution costs of the transactions in the respective BCs 11-1 to 11-6 may be set independently of one another, in other words, may be different from one another.
Each BC 11 may be a transmission source, a transmission destination of a transaction, or both. For convenience, the example of
The CC 12 is a network that connects multiple BCs 11 and may provide a service to perform mixing on transactions communicated among the BCs 11, for example. The CC 12 may obtain an execution cost of a transaction in each of the multiple BCs 11.
As illustrated in
As illustrated in
In this case, since the BC 11-1 generates three transactions, the BC 11-2 generates two transactions, and the BC 11-3 generates one transaction, the transmission source BCs 11 generate six (k) transactions in total. One of these six transactions is the genuine transaction and the remaining five (k−1) are the fake transactions. The six transactions are mixed in the CC 12 and sent to the respective transmission destination BCs 11-4 to 11-6 of the transactions.
In the transmission destination BCs 11, among the total six (k) transactions including one genuine transaction and five (k−1) fake transactions, three transactions are transmitted to the BC 11-4, two transactions are transmitted to the BC 11-5, and one transaction is transmitted to the BC 11-6.
In this way, in the system 1 according to the one embodiment, the CC 12 causes all the BCs 11 that can be targets of mixing service to generate transactions. This can cause the BC 11 that runs with a smaller execution cost to generate more fake transactions while inhibiting the genuine transaction from being uniquely identified, so that the execution cost of transactions can be reduced.
As another aspect, regardless of which BC 11 generates the genuine transaction, the total execution cost of the genuine transaction and the accompanied fake transactions generated in the system 1 (multiple BCs 11) can be kept constant or substantially constant. In other words, in the system 1 (CC 12), it is possible to equalize, among the BCs 11, the unevenness in the total execution cost caused by a difference in the BCs 11 of a user that issues the genuine transaction. Therefore, when operating a service to conceal a genuine transaction at a constant or substantially constant providing fee, this method can ensure fairness among users belonging to different BCs 11 and validity of the providing fee.
As illustrated in
The memory unit 2 has a storing region that stores various data used by the CC 12. The memory unit 2 may illustratively store genuine transaction information 2a, mixing helper information 2b, execution cost information 2c, and request information 2d.
As illustrated in
The “remittance source ID” is an example of identification information on the remittance sender (e.g., “User A”), and may be, for example, the address of a remittance sender in the remittance source BC 11. As one example, “A's address” may be set in the “remittance source ID”.
The “remittance source BC” is an example of identification information on the remittance source BC 11, and for example, an identifier such as “BC4” may be set.
The “remittance destination ID” is an example of identification information on a receiver (e.g., “User B”), and may be, for example, the address of the receiver in the remittance destination BC 11. As an example, “B's address” may be set in the “remittance destination ID”.
The “remittance destination BC” is an example of identification information on the remittance destination BC 11, and for example, an identifier such as “BC2” may be set.
The “remittance amount” is a remittance amount from the remittance sender, and for example, the amount of a virtual currency such as “500 coins” may be set.
The “contact details” is contact details of the remittance sender, and for example, an e-mail address such as “sender@XX.XX.XX” may be set.
As illustrated in
The “remittance source ID” is an example of identification information on a mixing helper (e.g., “User C”) and may be, for example, the address of the mixing helper in the remittance source BC 11. As one example, “C's address” may be set in the “remittance source ID”.
The “remittance source BC” is an example of identification information on the remittance source BC 11, and for example, an identifier such as “BC1” may be set.
The “remittance destination ID” is an example of identification information on a mixing helper (e.g., “User D”) and may be, for example, the address of the mixing helper in the remittance destination BC 11. As one example, “D's address” may be set in the “remittance destination ID”.
The “remittance destination BC” is an example of identification information on the remittance destination BC 11, and for example, an identifier such as “BC3” may be set.
The “remittance amount” is a remittable amount by the mixing helper, and for example, a threshold, a range, or a fixed money amount such as “1000 coins or less” or “500 coins” may be set.
The “contact details” are contact details for requesting mixing help to the mixing helper, and for example, an e-mail address such as “helper@XX.XX.XX” may be set.
The mixing helper may be registered in the mixing helper information 2b so as to transfer money to the addresses of two BCs 11 that a single helper possesses. This registration is only allowed if the addresses on the two BCs 11 are not associated with a single mixing helper.
In addition, even if a user possesses only an address of the remittance source BC 11 among the remittance source and the remittance destination, the user may be registerable as a mixing helper in such a manner that the user can help mixing passingly due to an occurrence of a scheduled remittance to the remittance destination BC 11.
In order to deal with the above-described manner, for example, as illustrated in
As illustrated in
The “blockchain” may be identification information on each BC 11, for example, an identifier such as “BC1”.
The “execution cost” is the relative execution cost of each BC 11. The “execution cost” may be determined, for example, on the basis of a virtual currency on the CC 12 based on the exchange rate of the value on the respective BCs 11. In the example of
The execution cost information 2c illustrated in
The request information 2d will be described below.
Returning to the description of
For example, as the transaction number “Tmin.” comes closer to a value k/N, transactions are generated more evenly at the BCs 11 and the higher privacy is guaranteed for a genuine transaction, but instead, the amount of reduction of the execution cost declines. Therefore, the transaction number “rind.” can be regarded as an example of a second privacy parameter for adjusting the trade-off between the concealment effect of the genuine transaction and the reduction effect of the execution cost.
For example, the transaction number determining unit 3 may obtain a point A at which the execution cost of the BC 11 having the largest execution cost, which corresponds to the execution cost “CN” of the “BCN” in the example of
The calculating process of the transaction number of each BC 11 may include, for example, the following processes of (i) and (ii).
(i) The transaction number determining unit 3 calculates the values a and b of the monotonically decreasing function f(x)=ax+b based on the condition illustrated in
For example, the transaction number determining unit 3 sums the mathematical expression of the transaction number T=execution cost C×a+b for all BCs 11, and obtains the following expressions (1) and (2) obtained by the summing.
“Tmin”=“CN”×a+b (1)
“T1”+ . . . +“Tmin”=k=(“C1”+ . . . +“CN”)×a+b (2)
(ii) The transaction number determining unit 3 substitutes “C1”, . . . , “CN−1” into the monotonically decreasing function f (x) to calculate “T1”, . . . , “TN−1”. Since “T1”, . . . , “TN−1” each can be a real number, the transaction number determining unit 3 may use, as a fractional process, rounding the calculation result to the nearest integer. The fractional process may include recording the processed fraction (the difference between the calculated real number and the rounded transaction number).
Further, the transaction number determining unit 3 determines whether or not “T1”+ . . . +“TN−1”+“Tmin”=k is satisfied and if the above sum is k−1, performs “+1” (addition of one) to “Tj” (j is an integer of 1 to N) having the largest difference from the real number. On the other hand, if the above sum is k+1, the transaction number determining unit 3 performs “−1” (subtraction of one) from “Tj” having the smallest difference from the real number.
The transaction number determining unit 3 outputs the “T1”, . . . , “TN−1” calculated by the illustrated calculating process and the second privacy parameter “Tmin” (“TN”) as the numbers of transactions to be generated in the “BC1” to “BCN”, respectively.
This obtains the respective transaction numbers of the multiple BCs 11 among which the transaction number to be generated in a BC 11 having the smallest execution cost, e.g., the transaction number “T1” of the “BC1”, comes to be the largest and the transaction number to be generated in a BC 11 having the largest execution cost, e.g., the transaction number “TN”=“Tmin” of the “BCN”, comes to be the smallest.
In the above assumption, when the execution costs of the “BC1”, the “BC2”, the “BC3”, and the “BC4” are “1”, “2”, “3”, and “4”, respectively, the transaction numbers T of the respective BCs 11 are respectively calculated to be “9”, “6”, “4”, and “1”, as illustrated in
As illustrated in
On the other hand, as illustrated in
If the execution cost of a case where a genuine transaction is generated in each of the “BC2”, the “BC3”, and the “BC4”, the total execution cost when a request for a genuine transaction is generated four times in total is calculated likewise to be “138” in the scheme of the one embodiment.
As such, in the example of
As described above, in relation to the inconvenience of the above first and the second comparative examples, the scheme of one embodiment can reduce the execution cost of the fake transactions while ensuring the concealment of the genuine transaction by inhibiting the genuine transaction from being uniquely identified.
In the example of
Returning to the description of
For example, the transaction generation requesting unit 4 may determine a mixing helper that satisfies the condition for the determined transaction number T by referring to the genuine transaction information 2a and the mixing helper information 2b. Then, the transaction generation requesting unit 4 may notify the contact details of the applicant of the genuine transaction and the specified mixing helper of a request to generate a transaction in helping the mixing (e.g., via e-mail transmission).
The transaction generation requesting unit 4 may store, as the request information 2d into the memory unit 2, for example, information related to the genuine transaction of the applicant to be a request target and fake transactions of the mixing helper.
Each of the applicant of a genuine transaction and the mixing helper requested by the transaction generation requesting unit 4 uses the terminal device 13 to perform a transaction execution process on its own remittance source BC 11. The transaction execution process may be implemented by any known techniques, for example.
The CA monitoring unit 5 monitors a connection chain account (CA) and monitors whether the genuine transaction and each fake transactions requested to the mixing helper are executed or not on the basis of the request information 2d.
For example, the CA monitoring unit 5 may confirm that all of the remittance source IDs included in the request information 2d made deposits corresponding to the remittance amounts into the CAs of the respective remittance source BCs 11. In the example of
In response to the receipt of the message “start transfer” from the CA monitoring unit 5, the credit transferring unit 6 executes a credit transferring process based on the request information 2d.
For example, in the credit transferring process, the credit transferring unit 6 applies, to the remittance destination BC 11, a transaction that requests deposits corresponding to the remittance amounts from the CAs of all remittance destination BCs 11 included in the request information 2d to the respective remittance destination IDs. In the example of
The processes performed by the CA monitoring unit 5 and the credit transferring unit 6 may be achieved by various known methods, for example. As an example, the CA monitoring unit 5, the credit transferring unit 6, or both may control the mixing of the transactions by a method similar to that performed by the CC 120 according to the second scheme described above.
As described above, the system 1 of the one embodiment can reduce the execution cost of fake transactions for concealing a genuine transaction of the concealing target as compared with the above-described second scheme.
Some BCs that handle virtual currencies adopt a scheme in which transactions are collectively executed using a micropayment mechanism to save the transaction execution cost. The system 1 according to the one embodiment can achieve the above-described advantages even when handling a transaction between virtual currencies that do not have a mechanism such as micropayment.
(1-4) Example of Operation:
(1-4-1) Determining Process:
As illustrated in
The transaction number determining unit 3 calculates solutions a and b of following simultaneous equations (Expressions (3) and (4)) (Step S2).
k=(“C1”+ . . . +“CN”)×a+b (3)
“Tmin”=“CN”×a+b (4)
The transaction number determining unit 3 sets an initial value “1” for a variable i being an integer of 1 to N (Step S3), and calculates “Ti”=“Ci”×a+b (Step S4).
The transaction number determining unit 3 performs a fractional process, for example, rounding, on the “Ti”, and records the difference “Δi” into the memory unit 2, for example (Step S5).
The transaction number determining unit 3 determines whether or not i=N is satisfied (Step S6), and when i=N is not satisfied (NO in Step S6), adds one to i (Step S7). Then the process proceeds to Step S4.
On the other hand, when i=N (YES in Step S6), the transaction number determining unit 3 determines whether or not “T1”+ . . . +“TN”=k is satisfied (Step S8), and when “T1”+ . . . +“TN”=k is satisfied (YES in Step S8), the process proceeds to Step S12.
If “T1”+ . . . +“TN”=k is not satisfied (NO in Step S8), the transaction number determining unit 3 determines whether or not “T1”+ . . . +“TN”<k is satisfied (Step S9).
If “T1”+ . . . +“TN”<k is satisfied (YES in Step S9), the transaction number determining unit 3 adds one to “Tj” (j is an integer of 1 to N) sequentially from Tj” having the maximum “Δj” until “T1”+ . . . +“TN”=k is satisfied (Step S10), and then the process proceeds to Step S12.
On the other hand, if “T1”+ . . . +“TN”<k is not satisfied (NO in Step S9), the transaction number determining unit 3 adds one to “Tj” sequentially from “Tj” having the smallest “Δi” until “T1”+ . . . +“TN”=k is satisfied (Step S11), and then the process proceeds to Step S12.
In Step S12, the transaction number determining unit 3 outputs the transaction numbers “T1”, . . . , “TN−1” to be generated in the respective BCs 11, for example, notifies the transaction generation requesting unit 4 of the transaction numbers, and then the process ends.
(1-4-2) Requesting Process:
As illustrated in
The transaction generation requesting unit 4 selects the mixing helper(s) from the mixing helper information 2b in accordance with the transaction numbers “T1”, . . . , “TN−1” (Step S22). For example, the transaction generation requesting unit 4 may select the mixing helper(s) such that the numbers “T1”, . . . , “TN−1” and “TN” of the transactions to the BCs 11 of the remittance source and destination, including the genuine transaction, are satisfied. At this time, the transaction generation requesting unit 4 may select, for example, only a candidate(s) that is capable of transferring the same amount of money as the remittance amount of the genuine transaction from the candidates for the mixing helper in the mixing helper information 2b.
The transaction generation requesting unit 4 determines whether or not a mixing helper that satisfies the above-described condition exists (whether or not a mixing helper that satisfies the condition is selected) in Step S22 (Step S23).
If a mixing helper that satisfies the condition does not exist (is not selected) (NO in Step S23), the transaction generation requesting unit 4 waits until the mixing helper information 2b is updated (Step S24), and then the process proceeds to Step S22.
If a mixing helper that satisfies the condition exists (is selected) (YES in Step S23), the transaction generation requesting unit 4 requests the applicant of the genuine transaction and the selected mixing helper to execute the transactions (Step S25).
The transaction generation requesting unit 4 updates the mixing helper information 2b (Step S26), and then the process ends. In Step S26, as described above, the transaction generation requesting unit 4 may store the requested applicant and mixing helper as the request information 2d into the memory unit 2.
Each of the requested applicant of the genuine transaction and the requested mixing helper may perform the transaction executing process on the remittance source BC 11 by using the terminal devices 13 that they use. The CC 12 may perform mixing of the generated transactions by the CA monitoring unit 5 and the credit transferring unit 6.
(1-5) Modification:
(1-5-1) First Modification:
The scheme of the one embodiment is useful, for example, when the probability of generation of a genuine transaction in each BC 11 is uniform or when a genuine transaction is generated frequently on a BC that runs with a high execution cost.
Incidentally, in the scheme of the second comparative example described above, all fake transactions are generated on the same BC 11 as that of the remittance sender of the genuine transaction.
As illustrated in
Therefore, the first modification will now describe a scheme that further reduces the execution cost by switching (selecting), based on a generation state of genuine transactions in the past, between the scheme of the one embodiment which is an example of a first generating process and the scheme of the second comparative example which is an example of a second generating process.
In the following description of the first modification, the configurations, the processes, or the functions that are not specifically mentioned are assumed to be the same as the configurations, the processes, or the functions according to the one embodiment described above.
The memory unit 2A may store a genuine transaction demanding (requesting) history 2e and generating method information 2f in addition to the information stored in the memory unit 2.
The “date of receipt” is a date (or date and time) on which a mixing request of a genuine transaction is received, and for example, a date such as “2020.09.02” may be set.
The “remittance source BC” is an identifier of the remittance source BC 11, such as “BC1”. The “remittance destination BC” is an identifier of the remittance destination BC 11, such as “BC3”.
The generating method information 2f is information indicating a generating method for a fake transaction to be applied in a next given time period, and for example, a value indicating the “second comparative example” or the “scheme of the one embodiment” may be set. The given time period is a preset time period and is an example of a first given time period. The given time period may be, for example, from a few minutes to several days or more, depending on the operation, the usage or the like of the system LA.
The generating method selecting unit 7 selects a generating method for a fake transaction of the next given time period from past genuine transaction requests based on the genuine transaction demanding history 2e and, for example, outputs a value indicating either one of the “second comparative example” and the “scheme of the one embodiment”. For example, the generating method selecting unit 7 may store, into the generating method information 2f, a generating method to be outputted.
The selecting process of the generating method by the generating method selecting unit 7 may include, for example, the following processes of (I) and (II).
(I) The generating method selecting unit 7 calculates, from the genuine transaction demanding history 2e, execution costs of one or more fake transactions generated when each of the methods of the one embodiment and the second comparative example is adopted for each of the n latest given time periods (n is an integer of one or more).
(II) The generating method selecting unit 7 determines the method that achieves low execution costs a larger number of times in the n latest given time periods as the generating method for a fake transaction of the next given time period. This means that the generating method selecting unit 7 selects a generating method for a fake transaction of the next given time period based on the result of comparison between the execution cost by the scheme of the one embodiment and the execution cost by the scheme of the second comparative example. The symbol n may represent, for example, an odd number, but is not limited thereto, and may be an even number.
The generating method selecting unit 7 may determine a method to be adopted in the next given time period by weighting so as to emphasize the nearer latest given time period in place of simple majority determination in the n given time periods.
The transaction generation requesting unit 4A makes the above-described request to the applicant and the mixing helper on the basis of the transaction number T to be generated in each BC 11 determined by the transaction number determining unit 3, using the generating method indicated by the generating method information 2f.
Next, an example of an operation in the system 1A according to the first modification will now be described.
First, by referring to
The generating method selecting unit 7 sets the initial value “0” for each of the variable “MethodA” for the second comparative example and the variable “MethodB” for the scheme of the one embodiment (Step S32). In the following description, the second comparative example is referred to as a method A, and the scheme of the one embodiment is referred to as a method B.
The generating method selecting unit 7 allocates past genuine transaction requests to n given time periods on the basis of dates of receipt (Step S33).
The generating method selecting unit 7 sets the initial value “1” for the variable i being an integer of 1 to N (Step S34). Then, the generating method selecting unit 7 calculates the execution cost “CA” of fake transactions when the method A is adopted in the time period i (Step S35). In addition, the generating method selecting unit 7 calculates the execution cost “CB” of fake transactions when the method B is adopted in the time period i (Step S36).
The generating method selecting unit 7 determines whether “CA”<“CB” is satisfied (Step S37). If “CA”<“CB” is not satisfied (NO in Step S37), adds one to “MethodA” (Step S38), and then the process proceeds to Step S40. On the other hand, if “CA”<“CB” is satisfied (YES in Step S37), the generating method selecting unit 7 adds one to “MethodB” (Step S39), and then the process proceeds to Step S40.
In Step S40, the generating method selecting unit 7 determines whether or not i=N is satisfied. If i=N is not satisfied (NO in Step S40), the generating method selecting unit 7 adds one to i (Step S41), and then the process proceeds to Step S35.
If i=N is satisfied (YES in Step S40), the generating method selecting unit 7 determines whether or not “MethodA”<“MethodB” is satisfied (Step S42).
If “MethodA”<“MethodB” is not satisfied (NO in Step S42), the generating method selecting unit 7 outputs information indicating the method A (denoted as [Method A]), for example, stores the information as the generating method information 2f into the memory unit 2A (Step S43), and then the process ends.
If “MethodA”<“MethodB” is satisfied (YES in Step S42), the generating method selecting unit 7 outputs information indicating the method B (denoted as [Method B]) (Step S44), and then the process ends.
Next, by referring to
As illustrated in
The transaction generation requesting unit 4A confirms the method indicated by the generating method information 2f. For example, the transaction generation requesting unit 4A determines whether or not the generating method information 2f indicates the method B (Step S52).
When the generating method information 2f is information indicating the method B (YES in Step S52), the process proceeds to Step S22. On the other hand, when the generating method information 2f is information indicating the method A (NO in Step S52), the transaction generation requesting unit 4A selects, from the mixing helper information 2b, “k−1” mixing helpers having the same remittance source BC 11 and the same remittance destination BC 11 of the genuine transaction (Step S53), and the process proceeds to Step S23.
(1-5-2) Second Modification:
The first modification described a case where the generating method for a fake transaction to be adopted in the next time period (next term) is determined in accordance with the BC 11 that has generated the past genuine transactions and the number of the generated transactions.
The second modification will now describe a scheme that determines the generating method for a fake transaction to be adopted in the next time period on the basis of total transaction numbers on the BCs 11 until the present time.
For example, a genuine transaction is generated when a user uses a token earned on a BC 11. Therefore, in a BC 11 where transactions are active, many users earn tokens, so that a large number of requests for genuine transactions are expected. In addition, a time lag often occurs from when a user earns a credit to when the user uses the credit.
Considering these tendency, the second modification describes a scheme that predicts the number of genuine transactions of the next given time period based on the overall transaction numbers on the BCs 11 (in past multiple given time periods) until the present time, and determines the generating method for a fake transaction to be adopted in the next time period on the basis of the predicted number of genuine transactions. The given time period according to the second modification is an example of the second given time period, and may be the same as or different from the given time period according to the first modification.
In the following description of the second modification, the configurations, the processes, or the functions that are not specifically mentioned are assumed to be the same as the configurations, the processes, or the functions according to the one embodiment described above.
The memory unit 2B may store the overall transaction history 2g in addition to the information that the memory unit 2A stores.
The “blockchain name” is the name of the target BC 11 of the entry, and for example, an identifier such as “BC1” may be set.
The “time period” is a period of counting the transactions, and for example, a period such as “September 2020” (i.e., one month) may be set.
The “transaction number” is the number of transactions generated on a BC 11 having the “blockchain name” during the “time period”, and for example, a numerical value such as “562,367” may be set.
The example of
The generating method selecting unit 7 selects a generating method for a fake transaction of the next given time period on the basis of the genuine transaction demanding history 2e and the overall transaction history 2g, and for example, outputs a value indicating either one of the “second comparative example” and the “scheme of the one embodiment”. For example, the generating method selecting unit 7B may store, into the generating method information 2f, a generating method to be outputted.
The selecting process of the generating method by the generating method selecting unit 7B may include, for example, the following processes of (III) to (IV).
(III) As illustrated in
(IV) As illustrated in
(V) The generating method selecting unit 7B calculates execution costs of fake transactions to be generated when the method of the scheme of the one embodiment and the second comparative example are adopted on the basis of the predicted genuine transaction number. Then, the generating method selecting unit 7B adopts a method having a smaller calculated execution cost to be the generating method for a fake transaction of the next given time period. The generating method selecting unit 7B may calculate the genuine transaction number of a BC 11 not exhibiting a high correlation in the process (III), using the value of the previous given time period.
Next, an example of the operation of the system 1B according to the second modification will now be described.
As illustrated in
Example of the time period information may include information on a variable M (M is an integer of two or more) that divides the previous date and time into multiple time periods, and a variable m that specifies each of the divided time periods. For example, if data for the last year is divided every one month, it means “M=12”, “m=1” means “last January” “m=M=12” means “last December”, and “m=M+1” means “this January”.
The generating method selecting unit 7B sets the initial value “1” for the variable i being an integer of 1 to N (Step S62). Then, the generating method selecting unit 7B calculates a correlation “ti” between the overall transaction number of the time period m from “m=1” to “m=M−1” and the genuine transaction number of the time period “m+1” (Step S63).
The generating method selecting unit 7B determines whether or not “T”>“ti” is satisfied (Step S64). If “T”>“ti” is satisfied (YES in Step S64), the generating method selecting unit 7B performs a regression analysis on the overall transaction number of the time period m from “m=1” to “m=M−1” and the genuine transaction number of the time period “m+1”. Then, the generating method selecting unit 7B predicts a genuine transaction number of the time period “M+1” as “tri” (Step S65) based on the result of the regression analysis and the overall transaction number of the time period M, and then the process proceeds to Step S67.
On the other hand, if “T”>“ti” is not satisfied (NO in Step S64), the generating method selecting unit 7B determines the genuine transaction number of the time period M as “tri” (Step S66), and then the process proceeds to Step S67. In Step S66, the generating method selecting unit 7B may alternatively determine, for example, the average value in the time period M (time periods from “m=1” to “m=M”) as “tri”.
In Step S67, the generating method selecting unit 7B determines whether i=N is satisfied. If i=N is not satisfied (NO in Step S67), the generating method selecting unit 7B adds one to i (Step S68), and then the process proceeds to Step S63.
If i=N is satisfied (YES in Step S67), the generating method selecting unit 7B calculates the execution cost “CA” of one or more fake transactions when the method A is adopted for the time period “M+1” on the basis of the values “tr1” to “trN” (Step S69). In addition, the generating method selecting unit 7B calculates the execution cost “CB” of fake transactions when the method B is adopted for the time period “M+1” on the basis of the values “tr1” to “trN” (Step S70).
The generating method selecting unit 7B determines whether or not “CA”<“CB” is satisfied (Step S71), and if “CA”<“CB” is not satisfied (NO in Step S71), outputs information indicating the method A (denoted as [Method A]), for example, stores the information as the generating method information 2f into the memory unit 2B (Step S72), and then the process ends.
If “CA”<“CB” is satisfied (YES in Step S71), the generating method selecting unit 7B outputs information indicating the method B (denoted as [Method B]) (Step S73), and then the process ends.
(1-6) Example of Hardware Configuration
An apparatus that achieves each of the CCs 12, 12A, and 12B of the above-described systems 1, 1A, and 1B may be a virtual server (VM; Virtual Machine) or a physical server. The functions of each of the CCs 12, 12A, and 12B may be achieved by one computer or by two or more computers. At least some of the functions of each of the CCs 12, 12A, and 12B may be implemented using HW (Hardware) resources and NW (Network) resources provided by cloud environments.
As illustrated in
The processor 10a is an example of an arithmetic processing device that performs various controls and calculations. The processor 10a may be connected to each block in the computer 10 via a bus 10i so as to be mutually communicable. The processor 10a may be a multi-processor including multiple processors or a multi-core processor having multiple processor cores, or may be configured to have multiple multi-core processors.
The processor 10a may be, for example, integrated circuits (ICs) such as CPUs (Central Processing Units), MPUs (Micro Processing Units), GPUs (Graphics Processing Units), APUs (Accelerated Processing Units), DSPs (Digital Signal Processors), ASICs (Application Specific ICs), FPGAs (Field-Programmable Gate Arrays), or a combination of two or more ICs described above.
The memory 10b is an example of an HW that stores information such as various data and programs. The memory 10b may be, for example, a volatile memory such as a DRAM (Dynamic Random Access Memory), a nonvolatile memory such as a PM (Persistent Memory), or both.
The storing device 10c is an example of an HW that stores information such as various data and programs. The storing device 10c may be, for example, various storage devices exemplified by a magnetic disk device such as an HDD (Hard Disk Drive), a semiconductor drive device such as an SSD (Solid State Drive), or nonvolatile memories. The non-volatile memory may be, for example, a flash memory, an SCM (Storage Class Memory), a ROM (Read Only Memory), or the like.
Various pieces of information stored in the memory units 2, 2A, and 2B illustrated in
The storing device 10c may store a program 10g (transaction control program) that achieves a part or all of various functions of the computer 10. For example, the processor 10a of the CCs 12, 12A, and 12B can achieve functions as the transaction number determining unit 3, the transaction generation requesting units 4 and 4A, the CA monitoring unit 5, the credit transferring unit 6, and the generation method selecting units 7 and 7B by expanding the program 10g stored into the storing device 10c onto the memory 10b and executing the program 10g.
The IF device 10d is an example of a communication IF that controls the connection and communication in at least one of a network in the CC 12, 12A, or 12B, a network between each BC 11 and the CC 12, 12A, or 12B, and a network between each terminal device 13 and the CC 12, 12A, or 12B. For example, the IF device 10d may include an adapter compatible with a LAN (Local Area Network) such as Ethernet (registered trademark), an optical communication such as FC (Fibre Channel), or the like. The adapter may be adapted to a communication scheme of at least one of a wireless scheme and a wired scheme. For example, the CCs 12, 12A, and 12B may be connected to each of the BCs 11 and the terminal devices 13 via the IF device 10d so as to be mutually communicable. For example, the program 10g may be downloaded from a network to the computer 10 via the communication IF and stored into the storing device 10c.
The I/O device 10e may include one of an input device and an output device, or both. The input device may be, for example, a keyboard, a mouse, or a touch panel. The output device may be, for example, a monitor, a projector, or a printer.
The reader 10f is an example of a reader that reads information on the data and programs recorded on a recording medium 10h. The reader 10f may include a connection terminal or a device to which the recording medium 10h can be connected or inserted. The reader 10f may be, for example, an adapter compatible with a USB (Universal Serial Bus) or the like, a drive device that accesses a recording disk, a card reader that accesses a flash memory such as an SD card, etc. The recording medium 10h may store the program 10g, and the reader 10f may read the program 10g from the recording medium 10h and store it into the storing device 10c.
The recording medium 10h may illustratively be a non-transitory computer-readable recording medium such as a magnetic/optical disk or a flash memory. The magnetic/optical disk may illustratively be a flexible disk, a CD (Compact Disc), a DVD (Digital Versatile Disc), a Blu-ray disk, an HVD (Holographic Versatile Disc), or the like. The flash memory may illustratively be a semiconductor memory such as a USB memory or an SD card.
The HW configuration of the computer 10 described above is merely illustrative. Thus, the HW of the computer 10 may appropriately undergo increase or decrease (e.g., addition or deletion of arbitrary blocks), division, integration in arbitrary combinations, and addition or deletion of the bus. For example, the CCs 12, 12A, and 12B may omit at least one of the I/O device 10e and the reader 10f.
(2) Miscellaneous:
The technique according to the one embodiment, and the first and second modifications described above can be changed or modified as follows.
For example, the one embodiment and the first and second modifications assume that the CCs 12, 12A and 12B each request a mixing helper of each BC 11 to generate a fake transaction, but the present invention is not limited thereto. Alternatively, the CCs 12, 12A and 12B (e.g., the function of the tumbler) may create an account that generates a fake transaction and may issue a fake transaction from the account.
Further, for example, the functional configurations included in each of the CCs 12, 12A, and 12B illustrated in
Further, for example, each of the CCs 12, 12A, and 12B illustrated in
As one aspect, the present invention can reduce an execution cost of a second transaction for concealing a first transaction of a concealing target.
Throughout the descriptions, the indefinite article “a” or “an”, or adjective “one” does not exclude a plurality.
All examples and conditional language recited herein are intended for the pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although one or more embodiments of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.
This application is a continuation application of International Application PCT/JP2020/042832 filed on Nov. 17, 2020 and designated the U.S., the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2020/042832 | Nov 2020 | US |
| Child | 18300438 | US |
