CN114547611A - Intelligent contract Pompe fraudster detection method and system based on multi-modal characteristics - Google Patents
Intelligent contract Pompe fraudster detection method and system based on multi-modal characteristics Download PDFInfo
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Abstract
The invention discloses an intelligent contract Ponconi deception bureau detection method and system based on multi-modal characteristics, wherein the method comprises the steps of firstly, carrying out sequencing representation learning on intelligent contract source codes to obtain global lexical characteristics; then, constructing an intelligent contract transaction attribute graph by utilizing static analysis, and extracting local transaction characteristics through a graph neural network; and (4) fusing global lexical features and local transaction features by using an attention mechanism, and carrying out intelligent contract detection of the Pompe deception on a secondary basis. The invention has the advantages that: the intelligent contract code semantics are fully extracted by combining two modal characteristics of the global lexical method and the local transaction of the intelligent contract, and the detection accuracy is improved; the program slicing technology and the code graph are used for representing that noise codes are removed while preserving the Pompe deception semantic related codes, so that the detection accuracy is improved; the detection method based on the code characteristics and the deep learning does not depend on other data and expert rules, improves the detection application range and efficiency, and reduces the detection cost.
Description
Technical Field
The invention belongs to the field of software security, and relates to an intelligent contract Pompe fraudster detection method and system based on multi-modal characteristics.
Background
A smart contract is a piece of software that runs on a blockchain platform. The system has characteristics of decentralization, incapability of tampering, anonymous execution and the like, and has attracted wide attention in numerous fields such as finance, investment, games and the like. With the widespread application of blockchain technology, a great deal of fraud is emerging on blockchain platforms, the most common of which is a pompe fraud based on intelligent contracts.
The pompe fraud is a common investment fraud that attracts investors through promises of high returns and pays the return of existing investors by approving the funds of new entry investors. The intelligent contract-based pompe frauds have the characteristics of automatic execution, anonymous transaction, difficult tracing and the like. Statistically, current intelligent contracts for pompe frauds have exceeded 2 million victims and cause economic losses of over $ 1.7 billion. How to detect intelligent contract detection of the Pompe fraudster becomes a problem to be solved urgently in block chain supervision.
The existing intelligent contract Pompe fraudster detection method comprises the following steps: 3 methods based on rules, neural network and transaction mode. The rule-based method relies on experts to define rules, and technologies such as symbolic execution or fuzzy test are utilized to search whether suspicious code segments meeting the rules of the experts exist in the codes. But the artificially defined rules are usually simple and lack flexibility, so that all possible scenarios cannot be completely covered, resulting in a high false alarm rate. The neural network-based method inputs all codes into the neural network as sequences, so that structural features and semantic features of the codes are lost, and the learning capability of the model is limited. And the code irrelevant to the Pompe fraudster in the codes is used as noise to interfere with the characteristic learning process of the neural network, so that the detection result is inaccurate. While the transaction pattern-based approach relies on past transaction data of the tested smart contract, this approach is applicable to active smart contracts where there is a large amount of transaction data. For those intelligent contract samples without sufficient transaction data, the detection effect of the method is poor, so that the application range of the method is small.
Disclosure of Invention
The purpose of the invention is as follows: in view of the problems in the prior art, the present invention aims to provide an intelligent contract pointcast cheating bureau detection method and system based on multi-modal characteristics, which have the advantages of more accurate detection, higher execution efficiency and wider application range.
The technical scheme is as follows: the invention provides an intelligent contract Pompe fraudster detection method based on multi-modal characteristics, which comprises the following steps of:
(1) constructing an intelligent contract source code data set, and marking a Pompe cheating intelligent contract sample in the data set by utilizing forum data and a manual auditing method;
(2) performing lexical analysis on the intelligent contract to obtain an abstract syntax tree, and developing the abstract syntax tree into a sequence by using a code structured traversal technology to obtain an intelligent contract serialized representation;
(3) program slicing is carried out on intelligent contract source codes by using grammatical features of the Pompe deception intelligent contract as slicing criteria, and sentences related to the Pompe deception semantic meanings are extracted to form a slice set; performing control flow and data flow analysis on the phrase set to construct an intelligent contract transaction attribute graph;
(4) performing feature extraction on the intelligent contract serialization input model by using a transform encoder as a feature extraction model to obtain an intelligent contract global feature vector;
(5) performing feature extraction on the intelligent contract transaction attribute graph by using a graph convolution neural network and graph self-attention pooling operation to obtain a local feature vector for intelligent contract transaction;
(6) and (5) fusing the global lexical feature vector and the local transaction feature vector of the intelligent contract obtained in the step (4) and the step (5) to obtain a composite feature vector of the intelligent contract, and inputting the composite feature vector of the intelligent contract into a multi-layer sensing machine to predict whether the current intelligent contract is a Pompe fraudster.
Further, the step (1) comprises the steps of:
(1.1) manually auditing the collected intelligent contract source codes, confirming whether the intelligent contract sample is a Pompe fraudster intelligent contract or not, and adding the intelligent contract confirmed as the Pompe fraudster intelligent contract into the Setponzi={c1,...,cN-wherein N represents the number of pointcast cheat intelligent contracts;
(1.2) collecting intelligent contract addresses through a BigQuery database, obtaining corresponding intelligent contract source codes through an Etherscan platform, manually confirming non-Ponz contract sample sets in the intelligent contract source codes, and forming the non-Ponz contract sample sets through the samplesno_ponzi={c1,...,cM-wherein M represents a non-pompe fraud intelligent contract sample number;
(1.2) integrating the intelligent contract samples obtained in the steps (1.1) and (1.2) to obtain an intelligent contract data Set (Set ═ Set)ponzi∪Setno_ponziAnd the intelligent contract sample number in the data set is S-M + N.
Further, the step (2) comprises the steps of:
(2.1) Using the solid compiler to sample the Smart contract ciCompiling the contract into an abstract syntax tree, traversing the abstract syntax tree, extracting a subtree with the root node type of functional definition, and constructing a current intelligent contract sample ciAbstract syntax tree collection of included functionsWherein K represents the current intelligent contract ciThe number of functions;
(2.2) abstracting the syntax tree of the function with a structured traversalExpansion into token sequenceWhereinRepresenting the length of a token sequence of the current function; merging token sequence sets of all functions to obtain a current intelligent contract sample ciIs shown in a serialized form(2.3) merging the serialized representations of all the intelligent contract samples to form an intelligent contract corpusTraining on the corpus by using a FastText model to obtain any tokeniCorresponding initial feature vector
Further, the step (3) includes the steps of:
(3.1) against Smart contract sample ciSet of abstract syntax tree of epsilon Set and function thereofTraversing all function abstract syntax trees using syntax analysisJudging whether the current function contains transfer operation, if so, adding the function into the sensitive function set corresponding to the current contract sampleThe rest of the functions forming a non-sensitive set of functions
(3.2) arbitrary function in the set of sensitivity functionsFor its abstract syntax treeSemantic analysis is carried out to obtain the function program dependence graphUsing 3 transfer transaction interfaces as slicing criteria, according to the principle of graph accessibilityBackward slicing is carried out to obtain a transaction slice attribute graph of the current functionAnd the node V epsilon V in the graph represents a function fiThe statement with semantic dependency relation with transaction behavior, wherein an edge E belongs to E in the graph, and the statement comprises the following components: control flow, data flow, control dependence and data dependence;
(3.3) traversalAnd searching global variables used by all nodes in the current function fiTransaction sensitive global variable set ofMerging the transaction sensitive global variables in all sensitive functions to obtain the current intelligent contract ciTransaction sensitive global variable set of
(3.4) traverse the current intelligent contract sample ciMiddle non-transaction sensitive functionCorresponding to the abstract syntax tree, judging whether the function uses transaction sensitive global variablesIf used, the current function is aggregated from the non-transaction sensitive functionsTransition to transaction sensitive function setAnd generating a transaction slice attribute graph of the current function by taking the transaction sensitive global variable used by the function as a slice criterion
(3.5) Global variables sensitive to arbitrary transactionsTraversing the current intelligent contract to find the definition statement of the variable to form a global variable definition statement set Vdef(ii) a Merging the transaction slice attribute map of all transaction sensitive functions and the global variable definition statement set VdefGenerating a contract transaction attribute map TPG (V, E) of the current contract sample; wherein the node V belongs to V and represents statements such as transaction sensitive global variable definition, transaction sensitive global variable use, transaction interface calling and the like related to transaction behaviors in the current intelligent contract; the edge E E in the figure comprises: data flow, control flow, data dependency, control dependency, and transaction sensitive variable modification.
Further, the step (4) comprises the steps of:
(4.1) for any Intelligent contract sample ciGenerating (2.3) a serialized representation of the current sampleDividing the batch into a plurality of batchs, wherein the number of tokens contained in each batch is l';
(4.2) calculating the position encoding vector PE of each token aiming at any batch, wherein the calculation method comprises the following steps:
PE(pos,2i)=sin(pos/100002i/d)
PE(pos,2i+1)=cos(pos/100002i/d)
wherein pos represents the position of the current token in batch; d is the dimension of the vector when token position encoding; i represents the index of the position-coding vector;
(4.3) adding the position coding vector of the token and the initial feature vector of the token to obtain the token in the current batchiInitialization vector ofMerging all token initialization vector representations in all batchs to obtain intelligent contract serialization representationWherein the content of the first and second substances,representing the vector representation corresponding to the jth batch; d represents the feature vector dimension of each token; l' is the number of tokens in batch; n is a radical ofbatchA quantity of lots representing a sequence of intelligent contracts;
(4.4) serializing the Intelligent contract representationInputting the characteristics into a multi-head self-attention module for feature learning; the multi-head attention mechanism has J attention heads, and the dimension of the characteristic vector output by the multi-head self-attention module is dmultiheadFor each attention headiThe learning characteristics are as follows:
wherein the content of the first and second substances,representing a matrix formed by feature vectors of all tokens in the jth batch; wi Q、Wi KAnd Wi VAre learnable parameters of the current attention head and have dimensions ofdhead=dmultiheadJ; combining the results of all attention heads to obtain the output of the current multi-head attention mechanism:
(4.5) outputting a multi-head attention mechanismAnd the original input XciResidual error connection is carried out and the residual error is input into a feedforward network through layer normalization operation to obtain the h-th global feature vector representation of the current intelligent contractg:
hffn_in=LayerNorm(X+hmultihead(X))
hg=max(0,hffn_inW1 ffn+b1)W2 ffn+b2
Further, the step (5) includes the steps of:
(5.1) for any Intelligent contract sample ciE Set corresponding transaction attribute graphWherein any node represents a statement in a contract; drawing (A)The initial feature vector of any node in the set is represented as: the sum of all token initial vectors in the current node; firstly, carrying out token sequence expansion on any node to obtain v ═ token1,...,tokennFourthly, calculating a node v in the graphiInitial feature vector ofComprises the following steps:
(5.2) any node v in the graphiWith a neighboring node vje.N (i) passing edge e(i,j)Connection, current node viThe state update formula for the convolution layer in the t-th graph is:
wherein the content of the first and second substances,cascading current node characteristics, neighbor node characteristics and the mutual relation between the two nodes as the input of state updating so that the model can learn the interaction between the nodes; andis a learnable parameter of the current convolutional layer; the final characteristic vector of any node v in the graph obtained by the T-layer graph convolution layer is expressed as
(5.3) utilization of the drawingsEach node V in the set belongs to V initial characteristic vectorFinal feature vectorObtaining local feature vector of current intelligent contract
Where, conv stands for one-dimensional convolution operation,is the number of nodes in the slice code property graph, σ (-) represents the activation function.
Further, the step (6) comprises the steps of:
(6.1) sample c for the current intelligent contractiCorresponding global featuresAnd local featuresRespectively calculating the corresponding attention weights in the following calculation modes:
wherein, Wg、Wl、bgAnd blIs a learnable parameter;
(6.2) weighting the global and local features by using the attention weight to obtain a final feature vector of the current intelligent contractRepresents:
and (6.3) inputting the generated final feature vector of the intelligent contract into a multilayer sensing machine, and judging whether the current intelligent contract is a Pompe deception intelligent contract.
Based on the same inventive concept, the invention also provides an intelligent contract Pompe fraudster detection system based on multi-modal characteristics, which comprises:
the data set construction module is used for constructing an intelligent contract source code data set; collecting intelligent contract source codes by utilizing forum data, and marking whether the intelligent contract sample is a Pompe cheat or not by utilizing a manual auditing method;
the serialization representation module is used for obtaining the intelligent contract serialization representation; firstly, carrying out lexical analysis on intelligent contract codes to obtain an abstract syntax tree of the intelligent contract codes, and then carrying out serialized expansion by using a structured traversal technology to obtain code serialized representation;
the transaction attribute graph extraction module is used for extracting local semantic features related to transaction behaviors in the intelligent contract; the nodes in the transaction attribute graph are composed of statements related to transaction behaviors; the edges in the transaction attribute graph comprise a plurality of semantic types such as a data dependence edge, a data flow edge, a control flow and a control dependence edge;
the intelligent contract global feature extraction module is used for extracting global lexical features of the intelligent contracts; extracting global features from the intelligent contract serialization representation by using a transformer encoder model;
the intelligent contract local transaction feature extraction module is used for extracting transaction related local features from the intelligent contract transaction attribute graph by utilizing a graph convolution neural network and graph self-attention pooling;
the multi-mode feature fusion detection module is used for fusing global features and local transaction features by using a multi-head attention mechanism to obtain a current intelligent contract composite feature representation; and inputting the composite characteristics into a multi-layer sensing machine to judge whether the current intelligent contract is a Pompe fraudster or not.
Has the advantages that: compared with the prior art, the invention has the following beneficial effects:
1. the invention automatically excavates the grammatical and semantic features of various types of Pompe fraudster intelligent contracts through a large number of intelligent contract samples training neural network models to carry out Pompe fraudster detection, and avoids the dependence on manually defined rules, so that the invention can obtain more accurate detection results, wider detection range and lower detection cost; meanwhile, the invention does not depend on any transaction data, so that the invention can detect whether the current investment object is the Pompe fraudster or not before the investor transacts with the intelligent contract of the Pompe fraudster;
2. the method accurately extracts the transaction behavior related code characteristics in the intelligent contract, considers the transaction behavior related code characteristics in and among functions, can more comprehensively reserve the semantic information related to transaction in the code, and simultaneously reduces the interference of other transaction unrelated codes on the model;
3. the invention considers various semantic relation information such as code control flow, data flow, control dependence, data dependence, variable modification and the like when extracting transaction related features, and the feature updating in the model is to input the semantic relation among different nodes into the model, thereby ensuring that the model can learn the features of different semantic relations;
4. the invention combines the global lexical characteristics and the local characteristics of the intelligent contract as the basis for detecting the Pompe frauds, wherein the global lexical characteristics fully utilize the code naturalness in the intelligent contract and improve the capability of a model for understanding the intention of an intelligent contract developer; the local features fully utilize the semantics of related codes of transaction behaviors in the intelligent contract and help the model to more accurately learn the transaction mode in the intelligent contract; by combining the code intention and the code transaction mode semantics, the model is helped to more accurately identify whether the current intelligent contract is a Pompe cheating contract.
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FIG. 1 is a flow chart of an intelligent contract Pompe fraudster detection method based on multi-modal features.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The invention provides an intelligent contract Pompe fraudster detection method based on multi-modal characteristics, which comprises the following steps of:
and constructing an intelligent contract source code data set, and marking a Pompe cheat intelligent contract sample in the data set by using forum data and a manual auditing method.
(1.1) collecting intelligent contract addresses disclosed as Pompe frauds in the bitcointalk forum and the dapprada forum, and collecting intelligent contract source codes corresponding to the addresses through an Etherscan platform. Manually auditing the collected intelligent contract source codes, confirming whether the intelligent contract sample is a Pompe fraudster intelligent contract or not, and adding the intelligent contract confirmed as the Pompe fraudster into the Setponzi={c1,...,cNWhere N represents the number of pointcast cheat intelligent contracts.
(1.2) collecting intelligent contract addresses through a BigQuery database, obtaining corresponding intelligent contract source codes through an Etherscan platform, manually confirming non-Ponz contract sample sets in the intelligent contract source codes, and forming the non-Ponz contract sample sets through the samplesno_ponzi={c1,...,cMWhere M represents the number of non-pompe fraud intelligent contract samples.
(1.3) integrating the intelligent contract samples obtained in the steps (1.1) and (1.2) to obtain an intelligent contract data Set (Set ═ Set)ponzi∪Setno_ponziAnd the intelligent contract sample number in the data set is S-M + N.
(1) Constructing an intelligent contract serialization representation; and performing lexical analysis on the intelligent contract to obtain an abstract syntax tree, and developing the abstract syntax tree into a sequence by using a code structured traversal technology to obtain the intelligent contract serialized representation.
(2.1) merging intelligence with a solidity compilerAbout sample ciCompiled into an abstract syntax tree. Traversing the abstract syntax tree, extracting a subtree with the root node type of functional definition, and constructing a current intelligent contract sample ciAbstract syntax tree collection of included functionsWherein K represents the current intelligent contract ciThe number of functions.
(2.2) abstracting the syntax tree of the function using the structured-based traversal method (SBT)Expansion into token sequenceWhereinRepresenting the length of the sequence of the current function token. Merging token sequence sets of all functions to obtain a current intelligent contract sample ciSerialized representation of
(2.3) merging the serialized representations of all the intelligent contract samples to form an intelligent contract corpusTraining on the corpus by using a FastText model to obtain any tokeniCorresponding initial feature vector
(2) Constructing an intelligent contract transaction attribute map representation; and (3) performing program slicing on the intelligent contract source code by using the grammatical features of the Pompe deception intelligent contract as a slicing criterion, and extracting semantic related sentences with the Pompe deception to form a slice set. And performing control flow and data flow analysis on the phrase set to construct an intelligent contract transaction attribute graph.
(3.1) against Smart contract samples ciSet of abstract syntax tree of epsilon Set and function thereofTraversing all function abstract syntax trees using syntax analysisJudging whether the current function contains transfer operation, if so, adding the function into the sensitive function set corresponding to the current contract sampleThe rest of the functions forming a non-sensitive set of functions
(3.2) arbitrary function in the set of sensitivity functionsFor its abstract syntax treeSemantic analysis is carried out to obtain the function program dependence graphUsing 3 transfer transaction interfaces as slicing criteria, according to the principle of graph accessibilityPerforming backward slicing to obtain the Transaction slice attribute Graph (STPG, Sliced Transaction Performance Graph) of the current functionAnd the node V epsilon V in the graph represents a function fiThe statement with semantic dependency relation with transaction behavior, wherein an edge E belongs to E in the graph and comprises: four types of control flow, data flow, control dependency and data dependency。
(3.3) traversalAnd searching global variables used by all nodes in the current function fiTransaction sensitive global variable set ofMerging the transaction sensitive global variables in all sensitive functions to obtain the current intelligent contract ciTransaction sensitive global variable set of
(3.4) traverse the current intelligent contract sample ciMiddle non-transaction sensitive functionCorresponding to the abstract syntax tree, judging whether the function uses transaction sensitive global variablesIf used, the current function is aggregated from the non-transaction sensitive functionsTransitioning to transaction sensitive function setAnd generating a transaction slice attribute graph of the current function by taking the transaction sensitive global variable used by the function as a slice criterion
(3.5) Global variables sensitive to arbitrary transactionsTraversing the current intelligent contract to find the definition statement of the variable to form a global variable definition statement set Vdef. Merging the transaction slice attribute map of all transaction sensitive functions and the global variable definition statement set VdefThe contract transaction attribute Graph (containtransactionproperty Graph) TPG of the current contract sample is generated as (V, E). Wherein the node V belongs to V and represents statements such as transaction sensitive global variable definition, transaction sensitive global variable use, transaction interface call and the like related to transaction behaviors in the current intelligent contract. The edge E E in the figure comprises: data flow, control flow, data dependency, control dependency, and transaction sensitive variable modification.
(3) And (3) performing feature extraction on the intelligent contract serialization input model by using a transformerecoder as a feature extraction model to obtain an intelligent contract global feature vector.
(4.1) for any Intelligent contract sample ciGenerating (2.3) a serialized representation of the current sampleThe device is divided into a plurality of batchs, and the number of tokens contained in each batch is l'.
(4.2) calculating the position encoding vector PE of each token aiming at any batch, wherein the calculation method comprises the following steps:
PE(pos,2i)=sin(pos/100002i/d)
PE(pos,2i+1)=cos(pos/100002i/d)
where pos represents the location of the current token in batch; d is the dimension of the vector when token position encoding; i represents the index of the position-coding vector.
(4.3) adding the position coding vector of the token and the initial feature vector of the token obtained in the step (2.3) to obtain the token in the current batchiInitialization vector ofMerging all token initialization vector representations in all batchs to obtain intelligent contract serialization representationWhereinRepresenting the vector representation corresponding to the jth batch; d represents the feature vector dimension of each token; l' is the number of tokens in batch; n is a radical ofbatchRepresenting the number of lots of the intelligent contract sequence.
(4.4) serializing the Intelligent contract representationInputting the multi-head self-attention module for feature learning. The multi-head attention mechanism has J attention heads, and the dimension of the characteristic vector output by the multi-head self-attention module is dmultiheadFor each attention headiThe learning characteristics are as follows:
representing a matrix formed by feature vectors of all tokens in the jth batch; wi Q、Wi KAnd Wi VAre learnable parameters of the current attention head and have dimensions ofWherein d ishead=dmultiheadand/J. Combining the results of all attention heads to obtain the output of the current multi-head attention mechanism:
(4.5) outputting a multi-head attention mechanismAnd the original inputResidual error connection is carried out and the residual error is input into a feedforward network through layer normalization operation, and the h-th global feature vector representation of the current intelligent contract is obtainedg:
hffn_in=LayerNorm(X+hmultihead(X))
hg=max(0,hffn_inW1 ffn+b1)W2 ffn+b2
(4) And performing feature extraction on the intelligent contract transaction attribute graph by using a graph convolution neural network and graph self-attention pooling operation to obtain a local feature vector for intelligent contract transaction.
(5.1) any intelligent contract samples c generated for step (3.5)iCorresponding trade attribute graph of e SetWhere any node represents a statement in a contract. The initial feature vector of any node in the graph is represented as: the sum of all token initial vectors in the current node. Firstly, carrying out token sequence expansion on any node to obtain v ═ token1,...,tokennAnd (4) reusing the initial feature vector of each token in the corpus generated in the step (2.3)Calculating a node v in a graphiInitial feature vector ofComprises the following steps:
(5.2) any node v in the graphiWith a neighboring node vje.N (i) passing edge e(i,j)Connection, current node viThe state update formula for the convolution layer in the t-th graph is:
whereinCascading current node characteristics, neighbor node characteristics and the mutual relation between the two nodes as the input of state updating so that the model can learn the interaction between the nodes; andis a learnable parameter for the current convolutional layer. The final characteristic vector of any node v in the graph obtained by the T-layer graph convolution layer is expressed as
(5.3) utilization of the drawingsEach node V in the set belongs to V initial characteristic vectorFinal feature vectorGet the currentLocal feature vector of intelligent contract
Where conv stands for a one-dimensional convolution operation,is the number of nodes in the slice code property graph, σ (-) represents the activation function.
(5) And (3) constructing a multi-mode feature fusion detection module based on an attention mechanism, fusing the global feature vector and the local transaction feature vector of the intelligent contract obtained in the steps (4) and (5) to obtain a composite feature vector of the intelligent contract, and inputting the composite feature vector of the intelligent contract into a multi-layer sensing machine to predict whether the current intelligent contract is a Pompe fraudster.
(6.1) sample c for the current intelligent contractiCorresponding global featuresAnd local featuresRespectively calculating the corresponding attention weights in the following calculation modes:
wherein Wg、Wl、bgAnd blAre learnable parameters.
(6.2) weighting the global and local features by using the attention weight to obtain a final feature vector of the current intelligent contractRepresents:
and (6.3) inputting the generated final feature vector of the intelligent contract into a multilayer sensing machine, and judging whether the current intelligent contract is a Pompe deception intelligent contract.
Based on the same inventive concept, the invention also provides an intelligent contract Pompe fraudster detection system based on multi-modal characteristics, which comprises:
the data set construction module is used for constructing an intelligent contract source code data set; collecting intelligent contract source codes by utilizing forum data, and marking whether the intelligent contract sample is a Pompe cheat or not by utilizing a manual auditing method;
the serialization representation module is used for obtaining the intelligent contract serialization representation; firstly, carrying out lexical analysis on intelligent contract codes to obtain an abstract syntax tree of the intelligent contract codes, and then carrying out serialized expansion by using a structured traversal technology to obtain code serialized representation;
the transaction attribute graph extraction module is used for extracting local semantic features related to transaction behaviors in the intelligent contract; the nodes in the transaction attribute graph are composed of statements related to transaction behaviors; the edges in the transaction attribute graph comprise a plurality of semantic types such as a data dependence edge, a data flow edge, a control flow and a control dependence edge;
the intelligent contract global feature extraction module is used for extracting global lexical features of the intelligent contracts; extracting global features from the intelligent contract serialization representation by using a transformer encoder model;
the intelligent contract local transaction feature extraction module is used for extracting transaction related local features from the intelligent contract transaction attribute graph by utilizing a graph convolution neural network and graph self-attention pooling;
the multi-mode feature fusion detection module is used for fusing global features and local transaction features by using a multi-head attention mechanism to obtain a current intelligent contract composite feature representation; and inputting the composite characteristics into a multi-layer sensing machine to judge whether the current intelligent contract is a Pompe fraudster or not.
In conclusion, the method utilizes the deep learning model to automatically learn the relevant global lexical features and the local transaction features of the Pompe fraudulent bureau from a large number of intelligent contract samples, and uses the attention mechanism to perform feature fusion, so that the detection model can efficiently and comprehensively learn the code semantics, and the detection effect and the detection efficiency of the Pompe fraudulent bureau are improved. When global lexical features are extracted, an abstract syntax tree is expanded by using a structured traversal technology, and global natural language features of the intelligent contract are fully learned by inputting a multi-head attention mechanism. When local transaction characteristics are extracted, intelligent contract codes are subjected to slicing processing by utilizing Pompe deception semantics to obtain transaction related grammars and semantic characteristics, interference of unrelated codes on a model is reduced, the transaction related codes are represented by a graph structure, and the grammars, semantic information and a context structure can be fully reserved. On the basis of global and local feature extraction, an attention mechanism is utilized to perform feature fusion and Pompe fraudster detection, and the low accuracy and high manual dependence of the traditional Pompe fraudster detection method are improved, so that the application range of detection is widened, and the detection cost is reduced.
Claims (8)
1. An intelligent contract Pompe fraudster detection method based on multi-modal characteristics is characterized by comprising the following steps of:
(1) constructing an intelligent contract source code data set, and marking a Pompe cheating intelligent contract sample in the data set by utilizing forum data and a manual auditing method;
(2) performing lexical analysis on the intelligent contract to obtain an abstract syntax tree, and developing the abstract syntax tree into a sequence by using a code structured traversal technology to obtain an intelligent contract serialized representation;
(3) program slicing is carried out on intelligent contract source codes by using grammatical features of the Pompe deception intelligent contract as slicing criteria, and sentences related to the Pompe deception semantic meanings are extracted to form a slice set; performing control flow and data flow analysis on the phrase set to construct an intelligent contract transaction attribute graph;
(4) performing feature extraction on the intelligent contract serialization input model by using a transform encoder as a feature extraction model to obtain an intelligent contract global feature vector;
(5) performing feature extraction on the intelligent contract transaction attribute graph by using a graph convolution neural network and graph self-attention pooling operation to obtain a local feature vector for intelligent contract transaction;
(6) and (5) fusing the global lexical feature vector and the local transaction feature vector of the intelligent contract obtained in the step (4) and the step (5) to obtain a composite feature vector of the intelligent contract, and inputting the composite feature vector of the intelligent contract into a multi-layer sensing machine to predict whether the current intelligent contract is a Pompe fraudster.
2. The intelligent contract pompe fraud detection method based on multi-modal features of claim 1, wherein said step (1) comprises the steps of:
(1.1) manually auditing the collected intelligent contract source codes, confirming whether the intelligent contract sample is a Pompe fraudster intelligent contract or not, and adding the intelligent contract confirmed as the Pompe fraudster intelligent contract into the Setponzi={c1,...,cN-wherein N represents the number of pointcast cheat intelligent contracts;
(1.2) collecting intelligent contract addresses through a BigQuery database, obtaining corresponding intelligent contract source codes through an Etherscan platform, manually confirming non-Ponz contract sample sets in the intelligent contract source codes, and forming the non-Ponz contract sample sets through the samplesno_ponzi={c1,...,cM-wherein M represents a non-pompe fraud intelligent contract sample number;
(1.1) integrating the intelligent contract samples obtained in the steps (1.1) and (1.2) to obtain an intelligent contract data Set (Set ═ Set)ponzi∪Setno_ponziAnd the number of intelligent contract samples in the dataset is S-M + N.
3. The intelligent contract pompe fraud detection method based on multi-modal features of claim 1, wherein said step (2) comprises the steps of:
(2.1) Using the solid compiler to sample the Smart contract ciCompiling to abstract syntaxTraversing the abstract syntax tree, extracting the subtree with the root node type of functional definition, and constructing the current intelligent contract sample ciAbstract syntax tree collection of included functionsWherein K represents the current intelligent contract ciThe number of functions;
(2.2) abstracting the syntax tree of the function with a structured traversalExpansion into token sequenceWhereinRepresenting the length of a token sequence of the current function; merging token sequence sets of all functions to obtain a current intelligent contract sample ciIs shown in a serialized form
4. The intelligent contract pompe fraud detection method based on multi-modal features of claim 1, wherein said step (3) comprises the steps of:
(3.1) against Smart contract samples ciE Set and its function extractionElephant syntax tree setTraversing all function abstract syntax trees using syntax analysisJudging whether the current function contains transfer operation, if so, adding the function into the sensitive function set corresponding to the current contract sampleThe rest of the functions forming a non-sensitive set of functions
(3.2) arbitrary function in the set of sensitivity functionsFor its abstract syntax treeSemantic analysis is carried out to obtain the function program dependence graphUsing 3 transfer transaction interfaces as slicing criteria, according to the principle of graph accessibilityBackward slicing is carried out to obtain a transaction slice attribute graph of the current functionAnd the node V epsilon V in the graph represents a function fiThe statement with semantic dependency relation with transaction behavior, wherein an edge E belongs to E in the graph, and the statement comprises the following components: control flow, data flow, control dependence and data dependence;
(3.3) traversalAnd searching global variables used by all nodes in the current function fiTransaction sensitive global variable set ofMerging the transaction sensitive global variables in all the sensitive functions to obtain the current intelligent contract ciTransaction sensitive global variable set of
(3.4) traverse the current intelligent contract sample ciMiddle non-transaction sensitive functionCorresponding to the abstract syntax tree, judging whether the function uses transaction sensitive global variablesIf used, the current function is aggregated from the non-transaction sensitive functionsTransitioning to transaction sensitive function setAnd generating a transaction slice attribute graph of the current function by taking the transaction sensitive global variable used by the function as a slice criterion
(3.5) Global variables sensitive to arbitrary transactionsTraverse the currentThe intelligent contract finds the definition statement of the variable to form a global variable definition statement set Vdef(ii) a Merging the transaction slice attribute map of all transaction sensitive functions and the global variable definition statement set VdefGenerating a contract transaction attribute map TPG (V, E) of the current contract sample; wherein the node V belongs to V and represents statements such as transaction sensitive global variable definition, transaction sensitive global variable use, transaction interface calling and the like related to transaction behaviors in the current intelligent contract; the edge E E in the figure comprises: data flow, control flow, data dependency, control dependency, and transaction sensitive variable modification.
5. The intelligent contract pompe fraud detection method based on multi-modal features of claim 1, wherein said step (4) comprises the steps of:
(4.1) for any Intelligent contract sample ciGenerating (2.3) a serialized representation of the current sampleDividing the batch into a plurality of batchs, wherein the number of tokens contained in each batch is l';
(4.2) calculating the position encoding vector PE of each token aiming at any batch, wherein the calculation method comprises the following steps:
PE(pos,2i)=sin(pos/100002i/d)
PE(pos,2i+1)=cos(pos/100002i/d)
wherein pos represents the position of the current token in batch; d is the dimension of the vector when token position encoding; i represents the index of the position-coding vector;
(4.3) adding the position coding vector of the token and the initial feature vector of the token to obtain the token in the current batchiInitialization vector ofMerging all token initialization vector representations in all batchs to obtain intelligent contract serialization representationWherein the content of the first and second substances,representing the vector representation corresponding to the jth batch; d represents the feature vector dimension of each token; l' is the number of tokens in batch; n is a radical ofbatchA quantity of lots representing a sequence of intelligent contracts;
(4.4) serializing Intelligent contractsInputting the characteristics into a multi-head self-attention module for feature learning; the multi-head attention mechanism has J attention heads, and the dimension of the characteristic vector output by the multi-head self-attention module is dmultiheadFor each attention headiThe learning characteristics are as follows:
wherein the content of the first and second substances,representing a matrix formed by feature vectors of all tokens in the jth batch; wi Q、Wi KAnd Wi VAre learnable parameters of the current attention head and have dimensions ofdhead=dmultiheadJ; combining the results of all attention heads to obtain the output of the current multi-head attention mechanism:
(4.5) outputting a multi-head attention mechanismAnd the original inputResidual error connection is carried out and the residual error is input into a feedforward network through layer normalization operation to obtain the h-th global feature vector representation of the current intelligent contractg:
hffn_in=LayerNorm(X+hmultihead(X))
6. The intelligent contract pompe fraud detection method based on multi-modal features of claim 1, wherein said step (5) comprises the steps of:
(5.1) for any Intelligent contract sample ciCorresponding trade attribute graph of e SetWherein any node represents a statement in a contract; the initial feature vector of any node in the graph is represented as: the sum of all token initial vectors in the current node; firstly, carrying out token sequence expansion on any node to obtain v ═ token { token1,...,tokennFourthly, calculating a node v in the graphiInitial feature vector ofComprises the following steps:
(5.2) any node v in the graphiWith a neighboring node vje.N (i) passing edge e(i,j)Connection, current node viThe state update formula for the convolution layer in the t-th graph is:
wherein the content of the first and second substances,cascading current node characteristics, neighbor node characteristics and the mutual relation between the two nodes as the input of state updating so that the model can learn the interaction between the nodes; andis a learnable parameter of the current convolutional layer; the final characteristic vector of any node v in the graph obtained by the T-layer graph convolution layer is expressed as
(5.3) utilization of the drawingsEach node V belongs to V initial characteristic vectorFinal feature vectorObtaining local feature vector of current intelligent contract
7. The intelligent contract pompe fraud detection method based on multi-modal features of claim 1, wherein said step (6) comprises the steps of:
(6.1) sample c for the current intelligent contractiCorresponding global featuresAnd local featuresRespectively calculating the corresponding attention weights in the following calculation modes:
wherein, Wg、Wl、bgAnd blIs a learnable parameter;
(6.2) weighting the global and local features by using the attention weight to obtain a final feature vector of the current intelligent contractRepresents:
and (6.3) inputting the generated final feature vector of the intelligent contract into a multilayer sensing machine, and judging whether the current intelligent contract is a Pompe deception intelligent contract.
8. An intelligent contract pompe fraud detection system based on multi-modal features using the method of any of claims 1-7, comprising:
the data set construction module is used for constructing an intelligent contract source code data set; collecting intelligent contract source codes by utilizing forum data, and marking whether the intelligent contract sample is a Pompe cheat or not by utilizing a manual auditing method;
the serialization representation module is used for obtaining the intelligent contract serialization representation; firstly, carrying out lexical analysis on intelligent contract codes to obtain an abstract syntax tree of the intelligent contract codes, and then carrying out serialized expansion by using a structured traversal technology to obtain code serialized representation;
the transaction attribute graph extraction module is used for extracting local semantic features related to transaction behaviors in the intelligent contract; the nodes in the transaction attribute graph are composed of statements related to transaction behaviors; the edges in the transaction attribute graph comprise a plurality of semantic types such as a data dependence edge, a data flow edge, a control flow and a control dependence edge;
the intelligent contract global feature extraction module is used for extracting global lexical features of the intelligent contracts; extracting global features from the intelligent contract serialization representation by using a transformer encoder model;
the intelligent contract local transaction feature extraction module is used for extracting transaction related local features from the intelligent contract transaction attribute graph by utilizing a graph convolution neural network and graph self-attention pooling;
the multi-mode feature fusion detection module is used for fusing global features and local transaction features by using a multi-head attention mechanism to obtain a current intelligent contract composite feature representation; and inputting the composite characteristics into a multi-layer sensing machine to judge whether the current intelligent contract is a Pompe fraudster or not.
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