KR20190122430A - Method of de-mixing for Bitcoin mixing services - Google Patents

Abstract

According to the present invention, a de-mixing method of a bitcoin mixing service comprises: an input/output information extracting process of being performed by a server monitoring a bitcoin transaction to extract information about at least one input address, at least one output address, an input amount inputted from each input address and an output amount moved to each output address by using bitcoin transaction information; an input/output matching combination extracting process of extracting an output combination matched with first input amount inputted from each input having each of the input addresses; and an input removing process of determining that corresponding output is matched with corresponding input and removing the corresponding input when the matched output is determined as one. It is possible to identify anonymized illegal bitcoin transaction by excluding the removed corresponding output and repeating the input/output combination extracting process and the input removing process.

Description

Method of de-mixing for Bitcoin mixing services}

The present invention relates to a method for demixing Bitcoin mixing service. More specifically, the present invention relates to a method for determining an illegal transaction having anonymity according to a bitcoin mixed service.

Bitcoin is a cryptocurrency created in 2009 by Satoshi Nakamoto. Since bitcoin addresses are proposed to be used only once, new addresses are created for each different transaction. Because Bitcoin addresses are randomly generated from the owner's private key and play a big role in the owner's anonymity, the address itself is difficult for a particular user to identify.

Nevertheless, Bitcoin can be difficult to fully guarantee the anonymity of a user. Thus, to overcome the limitations of anonymity and improve anonymity, mixed services can be introduced into the Bitcoin ecosystem. In a mixed service, a third party, called a mixer, mixes a plurality of Bitcoin transactions in a way that makes it impossible to grasp the association of input / output transactions from an outsider's point of view.

However, due to such anonymization by bitcoin transaction mixing, there is a problem that a crime such as a bitcoin illegal transaction occurs. Therefore, there is a need for a technique for preventing crimes such as illegal transactions while maintaining the anonymity of such Bitcoin transactions.

Accordingly, an object of the present invention is to provide a method for unmixing a bitcoin mixed service.

In addition, an object of the present invention is to provide a method for preventing crimes such as illegal transactions while maintaining the anonymity of Bitcoin transactions.

According to an aspect of the present invention to achieve the above or another object, in the de-mixing method of the bitcoin mixing service, the mixing de-mixing method is performed by a server monitoring the bitcoin transaction, bitcoin Input / output information for extracting information on at least one input address, at least one output address, input amount input from each input address, and output amount moved to each output address using transaction information. Extraction process; An input / output matching combination extraction step of extracting a combination of outputs matching the first input amount inputted at each input having each input address; And an input removing process of determining that the corresponding output is matched with the corresponding input when the matching output is determined as one, and removing the corresponding input, except for the removed corresponding input. By repeating the extraction process and the input removal process, anonymized illegal Bitcoin transactions can be identified.

According to an aspect of the present invention to achieve the above or another object, a server that performs a de-mixing method of the bitcoin mixing service, the interface for receiving bitcoin transaction information; And extracting information on at least one input address, at least one output address, an input amount input from each input address, and an output amount moved to each output address using the bitcoin transaction information. Extracting a combination of outputs matched with a first input amount input from each input having each input address, and when the matching output is determined as one, determining the output as matching with the corresponding input, And a control unit for removing the corresponding input, wherein the control unit repeats the input / output combination extraction process and the input removal process, except for the removed corresponding input, so that anonymized illegal bitcoin transaction can be identified. Do.

The method of unmixing the bitcoin mixed service according to the present invention has an advantage of preventing illegal transactions due to bitcoin anonymization.

Mixing release method of the bitcoin mixed service according to the present invention, there is an advantage that can prevent illegal transactions while maintaining the anonymity of the bitcoin transaction only by information that is disclosed at the time of bitcoin transactions.

1 illustrates a conceptual diagram of a bitcoin mixed service according to the present invention.
2 shows a flowchart of a method for unmixing a bitcoin mixing service according to the present invention.
3 is a flowchart illustrating a method of unmixing a bitcoin mixing service according to another embodiment of the present invention.
4 shows an example of a transaction for unmixing with the Bitcoin mixing service according to the present invention.
5 illustrates a transaction system for performing and monitoring a Bitcoin transaction service in accordance with the present invention.

The above-described features and effects of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, and thus, those skilled in the art to which the present invention pertains may easily implement the technical idea of the present invention. Could be. As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosure, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

In describing each drawing, like reference numerals are used for like elements.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term “and / or” includes any combination of a plurality of related items or any item of a plurality of related items.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art.

Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Should not.

The suffixes "module", "block", and "unit" for components used in the following description are given or mixed in consideration of ease of specification, and do not have distinct meanings or roles by themselves. .

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described to be easily carried out by those of ordinary skill in the art. In the following description of the embodiments of the present invention, when it is determined that the detailed description of the related known functions or known configurations may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, a detailed description will be given of a method of unmixing a bitcoin mixing service and a unmixing system according to the present invention. In this regard, the bitcoin mixing method according to the present invention will be described first.

Bitcoin mixed services improve the anonymity by breaking connections between addresses. In this regard, Figure 1 shows a conceptual diagram of a bitcoin mixed service according to the present invention. Referring to Figure 1, it consists of a plurality of inputs A, B, C and a plurality of outputs D, E, F. At this time, the mixer (mixer) mixes the input and output transactions in such a way that it is impossible to determine the correlation between the input and output transactions from the outsider's point of view. Thus, the anonymity (or anonymity) level is determined by the number of associated transactions.

This level of anonymity is proportional to the number of inputs, and the first step for analysis is to acquire transactions related to the mixed service. On the other hand, the mixed release method according to the present invention is to reduce the anonymization level by using other information such as transaction time and bitcoin (BTC) value. For example, if the value of input A and output F is 3 BTC, it is determined that these two input / output combinations are connected to each other with high probability. However, the mixed service may reflect various parameters in addition to the transaction time and bitcoin (BTC) values as follows.

In this regard, the capacities and parameters provided in the mixed service and release method according to the present invention will be described as follows.

Mixing Service Fee: This may be set by the user or randomly determined by the mixing service. The randomness of mixed costs makes it difficult to correlate input and output transactions.

Delay: If the mixed service creates an output transaction as soon as the mixed service mixes the input transactions, a time-based attack is easily possible. Therefore, the mixed service can avoid such an attack by setting a delay within a certain range. Therefore, the delay time between these transactions can be used to solve the mismatch problem, which will be described later, in addition to evading an attack, and also in case of anonymization release. However, as the range of delay increases, it may become more difficult or time-consuming to associate input and output transactions after mixing.

Max_output_address: A mixed service can split its input into multiple outputs. In addition, different delay times can be set for each input. Thus, splitting a transaction with different delays can make the demixing service more difficult. Thus, a combination of different mixing parameters can be considered for mixed service analysis.

Transaction Fee: Every time a transaction is created, Bitcoin can charge a transaction fee to the miner. Therefore, if the customer splits Bitcoin into several pieces, the transaction cost increases. In this regard, the mixed service may add costs for each address.

On the other hand, Figure 2 shows a flow chart of a method of mixing the bitcoin mixing service according to the present invention. Referring to FIG. 2, a method of mixing a bitcoin mixed service includes an input / output information extraction process (S110), an input / output combination extraction process (S120), and an input removal process (S130). In addition, the mixing release method of the bitcoin mixing service may further include a process of determining whether the input / output matching is complete (S140).

In this regard, the demixing method of the bitcoin mixing service may be performed by a server performing the mixing service and / or the demixing.

In the input / output information extraction process (S110), using bitcoin transaction information, at least one input address, at least one output address, an input amount input from each input address, and an output moved to each output address Extract information about the amount.

In the input / output combination extraction process (S120), a combination of outputs matching the first input amount inputted at each input having the respective input address is extracted.

In the input removing process (S130), when the matching output is determined as one, the corresponding output is determined to be matched with the corresponding input, and the corresponding input is removed.

In the input / output matching completion determination step (S140), it is determined whether the input removal process (S130) according to the matching is completed for all the inputs.

On the other hand, if it is determined that the matching is not completed for all inputs in the input / output matching determination process (S140), except for the removed input, the input / output combination extraction process (S120) and the input removal process (S130) may be repeated.

On the other hand, it can be implemented in another manner of the method for unmixing the bitcoin mixing service according to another embodiment of the present invention. In this regard, Figure 3 shows a flowchart of a method for unmixing the bitcoin mixing service according to another embodiment of the present invention. In this case, the mixing release method of the bitcoin mixing service includes an input / output information extraction process (S110), an input / output combination extraction process (S120), and an input removal process (S130) as described in FIG. 2. Meanwhile, the mixed release method of FIG. 3 may further include an illegal transaction determination process (S145) and an input / output combination removal process (S150). In this case, the illegal transaction determination process (S145) may be performed for all input / output matchable combinations according to all input removal processes (S130). Alternatively, the operation may be performed only on the input / output matching combination newly detected in the input removing process (S130). Alternatively, the operation may be performed only on newly detected input / output matching combinations for a certain time period (or a certain number of input removal processes S130).

On the other hand, in detail with respect to the mixing release method of the bitcoin mixing service in Figures 2 and 3 as follows. In this regard, Figure 4 shows an example of a transaction for unmixing with the Bitcoin mixed service according to the present invention. In addition, Table 1 shows a specific algorithm of the mixed release service according to the present invention.

For example, the mixing cancellation algorithm will be described in detail as follows. Referring to FIG. 4, three input transactions A, B, and C and three output transactions D, E, and F may be assumed for the mixed service. To determine the input / output transaction relationship, an algorithm can be started using the first transaction. In order to identify possible output transactions corresponding to an input transaction, the following two cases can be considered as candidate input transactions: (1) transaction D, or (2) having the same value as the bitcoin value of input transaction A Transaction E + F. At this point, since the output cannot be determined as one, we can temporarily store this state and check the next input. For the next transaction B, it can be seen that the output transaction that can match B is only E. Thus, the algorithm can eliminate the corresponding output E and determine one single output for A. At this time, it can be seen that the output transaction is D for the input transaction A. We can see that for the last input transaction C, the output transaction is F.

Therefore, the proposed demixing algorithm proceeds recursively to grasp the relationship with the transactions associated with the mixed service. On the other hand, this unmixing method is a more complex scenario with various mixing parameters such as mixing dealy, mixing service fee and number of output addresses, as well as bitcoin values for input / output matching. Should be considered.

Referring to Table 1, in the input / output matching combination extraction process (S110), for input Input _i , Input _i * time and Input _i Extract the output set OUTPUT 'within the time + Max_delay time range. In this case, the input Input _i has a value of 1 for the i-th input and a value of 0 for the remaining inputs. Also, since the bitcoin output value is smaller than the input Input _i , the value larger than Input _i is removed from OUTPUT '.

In addition, the output subset OUTPUT _subset may be extracted by storing all combinations of the output set OUTPUT 'until a preset Max_out is obtained.

Meanwhile, the 'De-mixing' algorithm of Table 1 describes the pseudo-code for the proposed demixing procedure. In the algorithm, N represents the number of inputs and M represents the number of outputs. Max_out represents the maximum number of output addresses, and the range of M is N ≦ M ≦ N * Max_out . Max_delay represents the maximum delay provided by the mixed service. INPUT = {Input ₁ , Input ₂ , ..., Input _N } and OUTPUT = {Output ₁ , Output ₂ , ..., Output _N } represent a set of input and output transactions, respectively. Input _i * time represents the time at which the input _i transaction occurred.

In the first step, for all outputs, the time at which the output transaction took place is Input _i * time and Input _i * time + Max_delay If within the time range, if the output value is smaller than the input transaction, when both conditions are satisfied, the algorithm stores it in OUTPUT '. In the second step, the algorithm calculates all possible combinations from OUTPUT 'and stores them in the OUTPUT _subset . If M 'is the size of OUTPUT', the size of the OUTPUT _subset is determined as shown in Equation 1 below.

In the third step, if the sum of each OUTPUT _subset equals (1-fee), the algorithm adds it to the Result set. If the magnitude is 1, the algorithm can determine that the associated output has been correctly identified. The matched output is removed from the OUTPUT and will not be included in the next procedure. The algorithm then repeats the above steps again in a recursive manner from the previously stored state. If any of the inputs does not have a size of Result set 1, the algorithm cannot determine the only output transaction associated with a given input transaction. However, according to the present invention, the number of possible outputs can be significantly reduced, so that a large number of input / output transactions can be matched even when anonymization is performed. This means that, according to the algorithm of the present invention, it is possible to determine with a higher probability the reduced number of candidate outputs is possible than selecting candidate outputs from a uniformly distributed set. Therefore, even when anonymization is performed in the recursive mixed mixing method according to the present invention, it can be seen that anonymization is effective for detecting illegal transactions and the like.

이다.In terms of complexity, the worst case can occur when no match is detected at all. At this time, since the size of the OUTPUT does not decrease, it is necessary to calculate all possible combinations of OUTPUT 'in step 2 of the algorithm. For one input, the combined operation must be performed | OUTPUT _subset | times, so the total time complexity is

to be.

On the other hand, the best case is when each matched output address is detected immediately. In this case, the size of M 'converges to one.

Meanwhile, when the result set has a size of 1 for all inputs of the input set INPUT, the repetition of the input / output combination extraction process S120 and the input removal process S130 may be stopped. In this case, if an input of which the size of the result set is not 1 is present, the size of the result set is determined to be 1 and an output corresponding to the removed input may be provided to the second server.

In addition, for an input of which the size of the result set is not 1, a combination of possible outputs and a probability of each output combination may be provided to the second server.

Mismatch may be referred to as an occurrence of an input other than the size of the result set. In this case, it is possible to determine whether the combinations that are possible with respect to the input having no input / output matching and which combination have the highest probability. For example, in the demixing method described above, weights may be weighted among the undetermined combinations of possible input / output combinations in the repetition of the respective steps. Based on the sum of the weights given in this iteration process, if the sum of the weights exceeds the threshold and it is determined that an illegal transaction has occurred, the bitcoin transaction for the corresponding input / output may be temporarily suspended.

On the other hand, the aforementioned mismatch is defined as a case where an input transaction cannot be associated with a unique output transaction. With regard to mismatch, two cases can be considered as follows. First, mismatches can occur when they have the same input value. In this regard, Table 2 shows the type, time and value for mismatch case 1.

Referring to Table 2, t _A2 , t _A3 and t _A4 are inputs of t _A1 , and t _B2 , t _B3 and t _B4 are inputs of t _B1 . Since t _A1 and t _B1 have the same input value, even if the number of output addresses is different, the sum of the output values becomes the same as in Equation 2 below.

Next, a mismatch may occur even if the input values are not the same. Table 3 shows the types, times, and values for mismatch case 2.

Referring to Table 3, t _C2 , t _C3 and t _C4 are inputs of t _C1 , t _D2 , t _D3 , t _D4 And t _D5 is the input of t _D1 . Where t _C2 + t _C4 = t _D2 + t _D3 + t _D4 + t _D5 If is satisfied, two cases are possible candidate sets as shown in Equation 3 below.

In summary, in the two cases described above, if the sum of the subset T _Xi generated in T _X equals the sum of the subset T _Yi produced in T _Y , for a given output sets T _X and T _Y This can happen.

On the other hand, probabilities of possible combinations for mismatches occurring for each of the aforementioned repetition processes may be generated. For example, based on disclosure information such as a transaction subscription time and a closing time and a transaction amount and a transaction price, a probability value of a transaction actually made during a mismatch occurring may be given. For each such iterative process, a probability of a combination of input / outputs according to the sum of probability values of a transaction may be provided to a second server, which is another server.

On the other hand, such a bitcoin mixed service and the mixed release is to prevent the transaction (anonymity) and the illegal transaction (illegal transaction) due to anonymization. Therefore, it is more important to release anonymization using this mixed release method for transactions considered to be illegal transactions.

In this regard, the information about each input and each output is anonymized by the bitcoin mixing service. In this case, the input / output combination extraction process (S120) and the input removal process (S130) may be repeated to release the anonymization.

Referring to FIG. 3, in the process of determining whether an illegal transaction is performed (S145), it is determined whether the bitcoin transaction is an illegal transaction. In this regard, based on the information on each of the inputs and the respective outputs obtained through the release of the anonymization and their traffic characteristics, it may be determined whether the bitcoin transaction is an illegal transaction. Can be.

On the other hand, if the bitcoin transaction is determined to be an illegal transaction, the method may further include an input / output combination removal process (S150) of removing all possible input / output combinations between the input and output associated with the illegal transaction.

On the other hand, if it is determined that the bitcoin transaction is not an illegal transaction, the input / output matching combination extraction process S120 and the input elimination process S130 may be repeated. In this case, the repetition is performed until the input / output combination is matched for all inputs or as shown in FIG. 2, or the input / output combination is determined to be matched for all inputs except mismatch cases. Can be.

Meanwhile, in the process of removing the input / output combination (S150), after removing all possible input / output combinations between the input and the output associated with the illegal transaction, the following process may be performed. That is, the input / output information extraction process (S110) may be performed between the input and the output not associated with the illegal transaction, and the input / output matching combination extraction process (S120) and the input elimination process (S130) may be repeated. have.

In the above, the mixing release method of the bitcoin mixing service according to the present invention has been described. Meanwhile, the above-described method of unmixing the bitcoin mixed service may be performed by a server managing and monitoring the bitcoin transaction service. In this regard, Figure 5 illustrates a transaction system for performing and monitoring a Bitcoin transaction service in accordance with the present invention. Referring to FIG. 5, a transaction system includes transmitting terminals 110, 120, and 130 performing input transactions A, B, and C and receiving terminals 210, 220, 230 performing output transactions D, E, and F. do. In addition, the server 300 further includes a server 300 that performs, manages and monitors bitcoin transactions between the transmitting terminals 110, 120, 130 and the receiving terminals 210, 220, 230. In addition, the server 300 may further include a second server 400 that manages and monitors a transaction independently of the server 300.

In addition, the server 300 includes an interface 310 for receiving bitcoin transaction information and a controller 320 for performing and controlling the bitcoin transaction. The controller 320 uses the bitcoin transaction information to determine at least one input address, at least one output address, an input amount input from each input address, and an output amount moved to each output address. Extract the information. In addition, the controller 320 extracts a combination of outputs matching the first input amount input from each input having the respective input address, and if the matching output is determined as one, the corresponding outputs and the corresponding inputs are determined. Determine as a match. In addition, the controller 320 may include a controller for removing the corresponding input, and the controller may repeat the input / output combination extraction process and the input removal process, except for the removed input.

Meanwhile, the controller 320 may perform all operations corresponding to the bitcoin mixed service and the release method thereof in the aforementioned specification. In addition, the controller 320 may cooperate with the second server 400 to perform a mixed release of the transaction. In detail, the controller 320 may provide the second server 400 with only the output for the input in which the size of the result set is determined to be 1 and thus removed. In addition, the controller 320 may provide the second server 400 with a combination of possible outputs and a probability of a combination of the outputs with respect to an input whose size of the result set is not 1.

The technical effects of the mixed release method and transaction system of the bitcoin mixed service according to the present invention are as follows.

In this regard, the mixed release method of the bitcoin mixing service according to the present invention has the advantage that it is possible to prevent illegal transactions due to bitcoin anonymization.

Mixing release method of the bitcoin mixed service according to the present invention, there is an advantage that can prevent illegal transactions while maintaining the anonymity of the bitcoin transaction only by information that is disclosed at the time of bitcoin transactions.

According to the software implementation, each component as well as the procedures and functions described herein may be implemented as separate software modules. Each of the software modules may perform one or more functions and operations described herein. Software code may be implemented in software applications written in a suitable programming language. The software code may be stored in a memory and executed by a controller or a processor.

Claims (8)

In the de-mixing method of bitcoin mixing service,
Input / output information for extracting information on at least one input address, at least one output address, input amount input from each input address, and output amount moved to each output address using bitcoin transaction information Extraction process;
An input / output combination extraction process of extracting a combination of outputs matching the first input amount inputted at each input having the respective input address; And
If the matching output is determined as one, the input is determined to be matched with the corresponding input, and the input removing process of removing the corresponding input includes:
Except for the removed input, repeating the input / output combination extraction process and the input removal process, Bitcoin mixed service. The method of claim 1,
In the input / output matching combination extraction process, for input Input _i , Input _i * time and Input _i extract the output set OUTPUT 'within the time + Max_delay time range-the input Input _i has a value of 1 for the i-th input and a value of 0 for the remaining inputs,
And extracting the output subset OUTPUT _subset by storing all combinations of the output set OUTPUT 'until a preset Max_out is obtained. The method of claim 2,
In the input removal process,
Input _i Compare the bitcoin value of (1-fee) with each of the OUTPUT _subsets ,
If the comparison result is the same, remove the input Input _i from the input set INPUT, remove the corresponding OUTPUT _subset from the output set OUTPUT ',
And determining the size of the result set of the removed input Input _i as 1. The method of claim 3,
If the size of the result set is 1 for all inputs of the input set INPUT, the repetition is stopped;
And if there is an input of which the size of the result set is not 1, the size of the result set is determined to be 1 so that only the output for the input removed is provided to the second server. The method of claim 4, wherein
And providing, for an input of which the size of the Result set is not 1, a combination of possible outputs and a probability of a combination of each output to the second server. The method of claim 1,
By the bitcoin mixed service, information about each input and each output is anonymized,
And releasing said anonymization by repeating said input / output combination extraction process and said input removal process. The method of claim 6,
On the basis of the information on each of the input and the respective output obtained through the release of the anonymization and their traffic characteristics, whether the bitcoin transaction is an illegal transaction (illegal transaction) determination whether the illegal transaction Include more courses,
If the bitcoin transaction is determined to be an illegal transaction, further comprising an input / output combination elimination process of removing all possible input / output combinations between the input and output associated with the illegal transaction. The method of claim 7, wherein
After removing all possible input / output combinations between input and output associated with the illegal transaction,
And performing the input / output information extraction process between the input and the output not associated with the illegal transaction, and repeating the input / output matching combination extraction process and the input elimination process.

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