Shard distribution device applied with sharding technique, method thereofm and blockchain network system including the same

Abstract

A method of operating a shard distribution device is disclosed. The method of operation includes the steps of distributing C nodes among n nodes into directory committee nodes based on the magnitudes of the confidence values ​​for n nodes, and randomly distributing (nC) nodes into k shards, with C nodes each, where n, C, and k are each natural numbers greater than or equal to 2.

Description

Technology Field

[0001] The present invention relates to a shard distribution device, and more particularly to a shard distribution device in which digital certificate-based trust security technology is applied to effectively defend against Sybil attacks in a blockchain environment where sharding techniques are applied, a method of operation thereof, and a blockchain network system including the same. Background Technology

[0002] Blockchain, based on Distributed Ledger Technology (DLT), guarantees data integrity and immutability and is utilized across various industries including cryptocurrency, smart contracts, finance, logistics, and healthcare. However, it faces scalability issues when applied to large-scale networks such as the Internet of Things (IoT).

[0003] To address this, sharding techniques have emerged that allow many transactions to be processed simultaneously across multiple shards, and various schemes such as ELASTICO, SSChain, and RapidChain are being used according to the system design objectives, depending on the shard distribution algorithm, consensus algorithm, and whether shards are reconfigured after consensus.

[0004] While sharding can solve the scalability problem of blockchains, security can be compromised by single shard takeovers, where an attacker seizes control of decision-making in the consensus process. Single shard takeovers can easily occur through Sybil attacks, which create multiple forged identities to disrupt consensus, undermine trust, and perform denial-of-service.

[0005] A digital certificate is an electronic document issued by a central Certificate Authority (CA) to a node; it is a Public Key Infrastructure (PKI)-based X.509 certificate containing information such as the owner, CA information, certificate validity period, signature algorithm, and digital signature.

[0006] The information listed above is the unique and immutable information of a node that attackers cannot easily forge or tamper with because it utilizes hash algorithms and the CA's private key. Therefore, when a Sybil attack is performed, it is possible to determine whether a node is a Sybil node by verifying the digital certificate information of multiple forged identities.

[0007] The authentication process based on digital certificates is performed through the Diameter Protocol, which is a type of authentication, authorization, and accounting protocol.

[0008] The Diameter protocol is already widely used in industrial IoT and mobile networks (e.g., 3G IMS (IP Multimedia Subsystem), 4G LTE (Long Term Evolution), and 5G NSA (Non-Standalone), etc.), and adopts a modular design, ensuring scalability for large-scale networks and interoperability in heterogeneous equipment environments. Prior art literature

[0009] Published Patent Application: Publication No. 10-2021-0003213 (Published Jan. 11, 2021) Registered Patent Application: Registration No. 10-2260093 (Registered May 28, 2021) Registered Patent Application: Registration No. 10-2337760 (December 6, 2021) The problem to be solved

[0010] The technical problem that the present invention aims to solve is to provide a shard distribution device and a method of operation thereof, and a blockchain network system including the same, which can ensure high throughput and security by effectively identifying Sybil nodes performing Sybil attacks in a blockchain environment where sharding techniques are applied, thereby reducing the impact of Sybil attacks and increasing the success rate of consultation. means of solving the problem

[0011] A method of operation of a shard distribution device according to an embodiment of the present invention comprises the steps of distributing C nodes among n nodes into Directory Committee nodes based on the magnitude of the confidence values ​​for n nodes, and randomly distributing (nC) nodes into k shards, each of which is C, and n, C, and k are each natural numbers greater than or equal to 2.

[0012] A shard distribution device according to an embodiment of the present invention comprises a confidence value evaluation device for calculating confidence values ​​for n nodes, and a distribution device for distributing C nodes among the n nodes as directory committee nodes based on the magnitude of the confidence values, and randomly distributing (nC) nodes to each of k shards in groups of C, wherein n, C, and k are each natural numbers greater than or equal to 2.

[0013] A blockchain network system according to an embodiment of the present invention comprises n nodes and a shard distribution device that distributes C nodes among the n nodes as directory committee nodes based on the magnitude of the trust values ​​for the n nodes, and randomly distributes (nC) nodes to each of k shards in groups of C, wherein n, C, and k are each natural numbers greater than or equal to 2. Effects of the invention

[0014] The shard distribution device and the method of operation according to an embodiment of the present invention have the effect of effectively identifying Sybil nodes performing Sybil attacks in a blockchain environment where a sharding technique is applied, thereby reducing the impact of Sybil attacks and increasing the success rate of negotiations, and ensuring high throughput and security. Brief explanation of the drawing

[0015] Detailed descriptions of each drawing are provided to help to more fully understand the drawings cited in the detailed description of the present invention. Figure 1 is a block diagram of a blockchain network system with sharding applied. Figure 2 is a flowchart for explaining the shard distribution and digital certificate-based authentication procedures performed in the blockchain network system illustrated in Figure 1. Figure 3 is a conceptual diagram illustrating the shard distribution shown in Figure 2. Figure 4 is a conceptual diagram illustrating a practical Byzantine fault-tolerant consensus performed in the blockchain network system illustrated in Figure 1. Figure 5 is a conceptual diagram illustrating the evaluation of node trust values ​​performed in the blockchain network system illustrated in Figure 1. Specific details for implementing the invention

[0016] Figure 1 is a block diagram of a blockchain network system with sharding applied.

[0017] Referring to FIG. 1, a blockchain network system (100) that operates in a P2P manner between nodes without a central server includes a Trust Authority (TA, 210), a Diameter Server (220), a Certificate Authority (CA, 230), and a blockchain network (300). The Trust Authority (210) can perform the function of a shard distribution device that distributes shards.

[0018] A CTBSD (Certificate based Trust Blockchain for Sharded Databases) model that adopts a Practical Byzantine Fault Tolerance (PBFT) consensus algorithm that can be used in a blockchain network system (100) increases the success rate of consensus by performing a shard reorganization procedure when more than one-third of the members suspected of being sybil, which may cause a disruption in consensus in a shard, are identified through a digital certificate-based authentication procedure.

[0019] Additionally, when the trust institution (210) combines the results of the observed node behavior during the consensus process with the authentication results to finally evaluate the trust value of the node in the corresponding round, it assigns a reward weight to the trust value of an honest node to further induce honest behavior in the next round, and assigns a punishment weight to the trust value of a sibyl node to weaken the influence of attacks in the next round. The trust value of the corresponding round is cumulatively averaged with the trust values ​​up to the previous round and used in the process of distributing shards based on the trust value when the next round begins.

[0020] FIG. 2 is a flowchart for explaining the shard distribution and digital certificate-based authentication procedures performed in the blockchain network system illustrated in FIG. 1, and FIG. 3 is a conceptual diagram for explaining the shard distribution illustrated in FIG. 2.

[0021] Referring to FIGS. 1 to 3, the distribution device (214) of the trust institution (210) distributes each of the n nodes (ND_1 to ND_n) into a plurality of shards (310, and 320_1 to 320_k) based on the magnitude of the trust value of each of the n nodes (ND_1 to ND_n). Here, n and k are each natural numbers greater than or equal to 2.

[0022] The trust value of a node is a score or indicator representing the degree to which the information or services provided by the node in the blockchain network can be trusted, and can be used for the detection and exclusion of malicious nodes or Sybil nodes. A Sybil node refers to a malicious node used in a Sybil attack.

[0023] First, it is assumed that the node confidence values ​​of each node (ND_1~ND_n) initially all have the same value.

[0024] In the process of electing (also referred to as 'distribution') the DC nodes (or members) that form the Directory Committee (DC) shard (310), even if a Sybil node is elected as the said DC node, it does not affect the final consensus by the authentication procedure already performed.

[0025] For example, a DC (Directory Committee) node may refer to a node in a blockchain or distributed network that assists in network information management (e.g., storing and maintaining node information of nodes included in the entire network and performing inter-node communication and data transfer using said node information), transaction verification (e.g., verifying transactions through a consensus protocol and contributing to consensus), and routing between nodes; said DC node primarily plays an important role in the consensus protocol and can contribute to ensuring the stability and efficiency of the network.

[0026] In each round of consensus, the trust value evaluation (or calculation) device (212) of the trust institution (210) can select C nodes (where C is a natural number greater than or equal to 2) as DC nodes in order of magnitude of the trust values ​​(e.g., descending order) from among the trust values ​​of n nodes (ND_1 to ND_n) (S110).

[0027] Since DC nodes are nodes with a high probability of reaching an honest consensus, they can guarantee the reliability of the final consensus and a high consensus success rate. A consensus round may refer to a short-term iterative cycle of the consensus process or block creation process in a blockchain network (300).

[0028] The distribution device (210) of the trust institution (210) selects C nodes as the C DC nodes distributed to the DC shard (310), and then randomly distributes the remaining (nC) nodes to each of the k shards (320_1~320_k) in groups of C (S110). That is, the distribution device (210) can randomly distribute the remaining (nC) nodes without considering the reliability of each of them.

[0029] For example, the distribution device (214) of the trust institution (210) can calculate the value of C according to Formula 1.

[0030] [Mathematical Formula 1]

[0031]

[0032] Here, means floor, and for example, when n is 102 and k is 4, C is 20.

[0033] According to embodiments, each device (212 and 214) of the trust institution (210) may be each program executed in a processor. In this case, the distribution program may calculate C using the Python programming language math.trunc(C) or the C++ programming language std::trunc(C).

[0034] When the configuration of the shards (310, and 320_1 to 320_k) is completed by the distribution device (214) of the trusted authority (210), the trusted authority (210) can generate node distribution information (NDI) and transmit it to the Diameter server (220).

[0035] For example, the node distribution information (NDI) in round (t) includes information about the shards (310, and 320_1 to 320_k) to which each of the n nodes (ND_1 to ND_n) belongs, and the confidence values ​​(TV1_1 to TV1_n) of each of the n nodes (ND_1 to ND_n).

[0036] Referring to FIG. 3, the first node (ND_1) is included in the DC shard (DCG or 310) and has a first confidence value (TV1_1), the second node (ND_2) is included in the first shard (SHD1 or 320_1) and has a second confidence value (TV1_2), the (n-1) node (ND_(n-1)) is included in the first shard (SHD1 or 320_1) and has a (n-1) confidence value (TV1_(n-1)), and the n-th node (ND_n) is included in the DC shard (DCG or 310) and has an n-th confidence value (TV1_n). Each unexplained node (ND_3 and ND_4) can be understood through the description of the first node (ND_1).

[0037] The Diameter Server (220) can perform an authentication procedure using the Diameter Protocol.

[0038] The Diameter Server (220) receives the certificates (CER1~CERn) of each of the n nodes (ND_1~ND_n) (S114), and generates an Online Certificate Status Protocol (OCSP) request (OCSP_R) to verify the validity of each certificate (CER1~CERn) and sends it to the Certificate Authority (230) (S116).

[0039] An OCSP request (OCSP_R) may include certificates (CER1~CERn) of each node (ND_1~ND_n) or information that can uniquely identify each certificate (CER1~CERn), and said information may include at least one of a unique identification number (serial number) of each certificate (CER1~CERn), a distinguished name (DN) of the CA (230) that issued each certificate (CER1~CERn), a nonce (i.e., a value for uniquely identifying the OCSP request (OCSP_R)), or a valid start date and expiration date (i.e., a period) of each certificate (CER1~CERn).

[0040] The certification authority (230) verifies whether each certificate (CER1~CERn) is valid (good), revoked, or unknown (unknown) according to the OCSP request (OCSP_R) (S118), and generates an OCSP response (VER) based on the verification result and sends it to the Diameter server (220) (S120). For example, the OCSP response (VER) may be encoded in ASN.1 (Abstract Syntax Notation One) format and sent to the Diameter server (220) (S120).

[0041] For example, the OCSP response (VER) may include a response status indicating whether the OCSP request (OCSP_R) was (1) successfully processed or an error occurred, (2) a response signature signed by the certification authority (230), (3) response data containing information on whether the certificate is valid, revoked, or unknown, and (4) a certificate ID that can identify the requested certificate (e.g., a unique identification number of the requested certificate and a unique name of the CA that issued the requested certificate).

[0042] Nodes with invalid certificates cannot participate in the consensus. For nodes with valid certificates, the Diameter server (220) can verify whether there is a duplicate certificate through the EAP-TLS (Extensible Authentication Protocol-Transport Layer Security) protocol, which is guaranteed to provide security performance encrypted by the Transport Layer Security (TLS) protocol (S122).

[0043] Since the certificate contains unique information that cannot be forged or altered, if the certificate is duplicated, the Diameter Server (220) can presume that a Sybil node created by a Sybil attacker has been identified (S122).

[0044] The Diameter server (220) can estimate the number of sibyl nodes for each shard (320_1 to 320_k) based on the OCSP response (VER) to the OCSP request (OCSP_R), and calculate the ratio of sibyl nodes (ENUM) based on the number of estimated sibyl nodes (S124). For example, the ratio of sibyl nodes (ENUM) is the ratio of the total number of nodes (C) included in the shard to the number of estimated sibyl nodes.

[0045] The Diameter server (220) determines whether the ratio of estimated Sybil nodes (ENUM) within each shard (320_1~320_k) is higher than a preset reference ratio (RNUM) (S126), and when the ratio of estimated Sybil nodes (ENUM) is higher than the reference ratio (RNUM) (YES in S126), since normal consensus cannot be reached within each shard (320_1~320_k), the Diameter server (220) sends a redistribution request to a trusted institution (210) to increase the consensus success rate (S128).

[0046] When the ratio of estimated Sybil nodes (ENUM) in each shard (320_1 to 320_k) is not higher than the reference ratio (RNUM) (NO in S126), that is, when the Practical Byzantine Fault Tolerance (PBFT) condition is satisfied in all shards (320_1 to 320_k) (NO in S126), the Diameter Server (220) sends a Local Block Generation Request (LBGR) to each shard (320_1 to 320_k) (S130). Accordingly, the distribution device (214) of the trust authority (210) performs step (S110).

[0047] Figure 4 is a conceptual diagram illustrating a practical Byzantine fault-tolerant consensus performed in the blockchain network system illustrated in Figure 1.

[0048] Referring to FIGS. 1 to 4, each primary node (PND_1 to PND_k) is randomly selected from each shard (320_1 to 320_k) according to a local block generation request (LBFR).

[0049] In the PBFT consensus algorithm, each primary node (PND_DC, and PND_1 to PND_k) selected per shard (310, and 320_1 to 320_k) is a node that proposes a transaction and acts proactively to obtain agreement from each of the nodes included in each node group (VLND_DC, and VLND_1 to VLND_k) for said transaction.

[0050] Each of the remaining nodes included in each shard (310, and 320_1 to 320_k), excluding each selected primary node (PND_DC, and PND_1 to PND_k), can become a validator node that validates the proposed transaction, for example, a local block, and perform validation of the transaction.

[0051] Each node group (VLND_DC, and VLND_1 to VLND_k) includes (C-1) nodes excluding each primary node (PND_DC, and PND_1 to PND_k).

[0052] Each shard (310, and 320_1 to 320_k) performing the PBFT consensus algorithm (or consensus processes (or consensus steps)) can sequentially proceed through the request step, pre-prepare step, prepare step, commit step, and reply step.

[0053] In the request phase, when a client, for example, a Diameter server (220), sends a request to create (or add) a local block to each primary node (PND_1 to PND_k) of each shard (320_1 to 320_k), each primary node (PND_1 to PND_k) proposing the creation of a local block creates the local block.

[0054] In the preliminary preparation phase, each primary node (PND_1~PND_k) propagates the proposed local block to (C-1) validator nodes included in each node group (VLND_1~VLND_k).

[0055] In the preparation phase, each of the (C-1) validator nodes included in each node group (VLND_1~VLND_k) reviews the local block proposed by each primary node (PND_1~PND_k), and if it is determined that the local block is valid, generates a consent message, which is a prepare message, and exchanges the prepare message with the (C-2) validator nodes included in each node group (VLND_1~VLND_k).

[0056] In the confirmation phase, when each of the (C-1) validator nodes receives a ready message at a predetermined ratio (e.g., agreement of 2 / 3 or more of the nodes), each of the (C-1) validator nodes included in each shard (320_1 to 320_k) confirms the local block (PNBL) and generates a commit message indicating that they are ready to add the local block (PNBL) to the blockchain containing the previous blocks (BL1 to BL3), and propagates it to each primary node (PND_1 to PND_k).

[0057] In the response phase, each primary node (PND_1~PND_k) receives confirmation messages from each of the (C-1) validator nodes included in each node group (VLND_1~VLND_k), determines whether to create the local block (PNBL) proposed to itself based on the received confirmation messages, and transmits the result of the decision to the Diameter Server (220).

[0058] If at least one malicious node is included in each node group (VLND_1~VLND_k) and the at least one malicious node does not generate a ready message or a confirmation message, or propagates an opinion (or message) contrary to the honest nodes, but does not exceed the PBFT bound, the consensus result by the honest nodes is not affected.

[0059] The PBFT bound is an important condition in the PBFT consensus algorithm that determines the maximum number of failed nodes and the minimum total number of nodes for which the system (100 or 300) can withstand Byzantine faults and achieve normal consensus.

[0060] For example, in the PBFT consensus algorithm, for the system (100 or 300) to function normally, the maximum number of nodes where a Byzantine failure can occur must be f, and the total number of nodes (n) of the system (100 or 300), i.e., n = 3f + 1.

[0061] Once a local block is created, the Diameter server (220) adds the local block (PNBL) as a final block to the blockchain containing blocks (BL1~BL3) through final consensus in the DC shard (310) according to the request phase, preparatory phase, preparation phase, confirmation phase, and response phase included in the PBFT consensus algorithm performed by the DC nodes included in the DC shard (310).

[0062] Figure 5 is a conceptual diagram illustrating the evaluation of node trust values ​​performed in the blockchain network system illustrated in Figure 1.

[0063] Referring to FIGS. 1 to 5, while consensus is being processed by the PBFT consensus algorithm, each validator node included in each node group (VLND_1 to VLND_k) of each shard (320_1 to 320_k) submits a message in favor or against the creation of a local block (PNBL) proposed by each primary node (PND_1 to PND_k).

[0064] In this process, the result of a specific node included in each shard (320_1 to 320_k) observing the behavior of each of the other nodes is collected as a Subjective Consensus Opinion (SCO) by a trust institution (210) as data in a vector array (1×n).

[0065] The trust organization (210) is included in the SCO and processes or stores it as 'Y' if it agrees (AGREE) to the creation of the local block (PNBL), and as 'R' if it disagrees (REJECT).

[0066] Since SCO is the subjective opinion of the node, the trust institution (210) aggregates all SCOs observed by any node (i) on another node (j) to calculate a Local Trust Opinion (LTO) expressed as in Equation 2, and produces LTO data (LTOD), which is an (n×n) LTO matrix.

[0067] [Mathematical Formula 2]

[0068]

[0069] Here, is the number of votes (Y) in the SCO of node (i), and is the number of opposites (R) in the SCO of node (i). Here, i is a natural number and can be any one from 1 to n.

[0070] The trust value evaluation device (212) of the trust institution (210) calculates the average of the column vectors of the (n×n) LTO matrix as in Equation 3 to determine the average subjective trust value, which determines how much the opinion submitted by node (j) matches the consensus result. Calculate ). Here, i is a natural number and can be any one from 1 to n.

[0071] [Mathematical Formula 3]

[0072]

[0073] Next, the trust value evaluation device (212) of the trust institution (210) calculates the average of the row vectors of the (n×n) LTO matrix using cosine similarity as in Equation 4 to determine how similar node (i) is to the opinion of each of the total nodes (e.g., (n-1) nodes) and the average trust similarity, which serves as an identification indicator for SCO tampering attacks Produces ).

[0074] [Mathematical Formula 4]

[0075]

[0076] Here, is the cosine similarity value between the row vectors of the nodes (i and j).

[0077] The reliability value evaluation device (212) of the trust institution (210) is the average subjective reliability value ( ) and average confidence similarity( Based on ) and the identity information of the nodes identified in the authentication process, the confidence value of each node in the consensus round (t) Calculate ) according to mathematical formula 5.

[0078] The trust value evaluation device (212) of the trust institution (210) provides a reward value ( ) is assigned differentially as shown in mathematical formula 5 to induce the honest node to perform honest behavior.

[0079] In addition, the trust value evaluation device (212) of the trust institution (210) gives a penalty ( By granting ), the trust value of the above copy node is lowered and Sybil influence is weakened.

[0080] For example, since each of the n nodes (ND_1 to ND_n) acts as a primary node or a validator node when it is an honest node or a sybil node, the confidence value evaluation device (212) determines whether each of the n nodes (ND_1 to ND_n) acted as a primary node or a validator node, and can assign different confidence values ​​to each of the n nodes (ND_1 to ND_n) according to the result of the determination.

[0081] [Mathematical Formula 5]

[0082]

[0083] Here, is the trust value when node (i) passes authentication ( ) and, is the trust value when node (i) fails authentication ( ) is. α is greater than 0 and less than 1. 0<α<1.

[0084] is the reward value, and This is a penalty. The reward value received when an honest node acts as a primary node is higher than the reward value received by a validator node.

[0085] The trust institution (210) can accurately identify the identity of the node by comprehensively judging the results of behavioral observations during the authentication process and the consensus process, and increase the success rate of consensus in the next consensus round (t+1).

[0086] The confidence value evaluation device (212) of the trust institution (210) evaluates the confidence value (of a node (i, 1≤i≤n)) calculated in the current round (t). The cumulative average of the confidence values ​​up to the previous round and ) is calculated as in Equation 6 and reflected in the shard distribution process when the next sum round (t+1) begins (S110).

[0087] [Mathematical Formula 6]

[0088]

[0090] The present invention has been described with reference to embodiments illustrated in the drawings, but this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims. Explanation of the symbols

[0091] 100: Blockchain Network System 210: Trusted Authority 212: Confidence value evaluation device 214: Distribution device 220: Diameter Server 230: Certification Authority 300: Blockchain Network ND_1~ND_n: Nodes 310: Directory Committee((Directory CommitteeConsensus(DC)) shard 320_1~320_k: Shard

Claims

Claim 1 A method of operating a shard distribution device comprising: (a) distributing C nodes among n nodes as directory committee nodes based on the order of magnitude of the confidence values ​​for n nodes; and (b) randomly distributing the remaining (nC) nodes, excluding the C directory committee nodes, into k shards, C nodes each without considering the confidence values, wherein n, C, and k are each natural numbers greater than or equal to 2. Claim 2 In paragraph 1, the above C is determined according to the following mathematical formula, [mathematical formula] Here, The operation method of a shard distribution device meaning floor. Claim 3 A method of operation of a shard distribution device according to claim 1, wherein step (a) comprises: determining whether each of the n nodes acted as a primary node or a validator node; assigning different trust values ​​to each of the n nodes according to the determination result; and distributing the C nodes to the directory committee nodes based on the trust values ​​assigned to the n nodes. Claim 4 A method of operation of a shard distribution device according to claim 1, wherein step (a) comprises: generating the confidence values ​​for the n nodes by calculating the cumulative average of the confidence values ​​for each of the n nodes up to the previous rounds; and distributing the C nodes to the directory committee nodes based on the magnitude of the confidence values ​​for the n nodes. Claim 5 A shard distribution device comprising: a confidence value evaluation device for calculating confidence values ​​for n nodes; and a distribution device for distributing C nodes among the n nodes as directory committee nodes based on the order of magnitude of the confidence values, and then randomly distributing the remaining (nC) nodes, excluding the C directory committee nodes, to each of k shards in groups of C without considering the confidence values, wherein n, C, and k are each natural numbers greater than or equal to 2. Claim 6 In paragraph 5, the distribution device is a shard distribution device that classifies the confidence values ​​in descending order according to the magnitude of the confidence values ​​and distributes the C nodes to the directory committee nodes based on the magnitude of the confidence values ​​classified in descending order. Claim 7 In paragraph 5, the distribution device determines C according to the following mathematical formula, [mathematical formula] Here, is a shard distribution device meaning floor. Claim 8 In claim 5, the distribution device is a shard distribution device that determines whether each of the n nodes acted as a primary node or a validator node, assigns different trust values ​​to each of the n nodes according to the determination result, and distributes the C nodes to the directory committee nodes based on the magnitude of the trust values ​​assigned to the n nodes. Claim 9 In paragraph 5, the distribution device is a shard distribution device that generates the confidence values ​​for the n nodes by calculating the cumulative average of the confidence values ​​for each of the n nodes up to the previous rounds, and distributes the C nodes to the directory committee nodes based on the magnitude of the confidence values ​​for the n nodes. Claim 10 A blockchain network system with a sharding technique applied, comprising: n nodes; and a shard distribution device that distributes C nodes among the n nodes as directory committee nodes based on the order of magnitude of the trust values ​​for the n nodes, and then randomly distributes the remaining (nC) nodes, excluding the C directory committee nodes, to each of k shards in groups of C without considering the trust values, wherein n, C, and k are each natural numbers greater than or equal to 2. Claim 11 A blockchain network system further comprising, in claim 10, a Diameter server that receives verification results for digital certificates for the n nodes from a certification authority, estimates the ratio of civil nodes among the nodes included in each shard based on the received verification results, and requests the redistribution of the n nodes to the shard distribution device or transmits a local block creation request to each of the k shards according to the estimated ratio of civil nodes. Claim 12 A blockchain network system according to claim 11, wherein each of the k shards performs Practical Byzantine Fault Tolerance (PBFT) consensus processes for the creation of a local block in response to the local block creation request to create the local block and transmits the creation result to the Diameter server, and the Diameter server creates the local block as a final block in accordance with the PBFT consensus processes performed in the Directory Committee shard including the Directory Committee nodes and adds it to the blockchain. Claim 13 A blockchain network system with a sharding technique applied, wherein, in claim 10, the system further includes a Diameter server that receives node distribution information for each of the n nodes from the shard distribution device, and the Diameter server receives digital certificates from the n nodes, generates an Online Certificate Status Protocol (OCSP) request containing information about the digital certificates for the n nodes and transmits it to a certification authority, receives a response to the OCSP request from the certification authority, determines whether duplicate certificates exist per shard based on the received response, estimates the nodes corresponding to the duplicate certificates per shard as Sybil nodes according to the determination result, determines whether the ratio of the Sybil nodes estimated per shard is greater than a reference ratio, requests redistribution to the shard distribution device when the ratio of the Sybil nodes estimated per shard is greater than the reference ratio, and transmits a local block request to each of the k shards when the ratio of the Sybil nodes estimated per shard is less than the reference ratio. Claim 14 In Clause 10, the above distribution device determines C according to the following mathematical formula, [mathematical formula] Here, A blockchain network system that applies a sharding technique meaning floor. Claim 15 A blockchain network system with a sharding technique applied in claim 10, wherein the distribution device determines whether each of the n nodes acted as a primary node or a validator node, assigns different trust values ​​to each of the n nodes according to the determination result, and distributes the C nodes to the directory committee nodes based on the magnitude of the trust values ​​assigned to the n nodes.

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