CN111538962A - Program control flow obfuscation method, system, storage medium, cloud server and application - Google Patents

Abstract

The invention belongs to the technical field of control flow obfuscation, and discloses a program control flow obfuscation method, system, storage medium, cloud server and application, which hide the judgment conditions of branch statements in an original program, and use a control flow query function to replace the judgment of branch statements Condition; further obfuscate the control flow by inserting pseudo-branch statements in the program; send the conversion program to an untrusted public cloud, and send the control flow matrix to a trusted private cloud; based on the control flow matrix, in the public cloud When running the conversion program on the cloud. The invention can hide the variables of the condition of each branch statement, avoiding malicious acquisition and utilization of application program logic by external attackers; inserting pseudo-branch statements increases the difficulty for attackers to reconstruct the program control flow; inserting relational constraint statements and performing data flow Consistency check prevents attackers from actively changing the running process of the program, and collects effective information by purposefully adding new data during the running of the program.

Description

Program control flow obfuscation method, system, storage medium, cloud server and application

technical field

The invention belongs to the technical field of control flow obfuscation, and in particular relates to a program control flow obfuscation method, system, storage medium, cloud server and application.

Background technique

At present, the security protection of program code is a key research content in the field of computer security. With the rapid development of the Internet and the arrival of the era of big data, cloud computing services are becoming more and more popular, and the cloud computing environment can bring users stronger computing power and better scalability. Cloud computing enables users to rent computing resources on demand and execute their programs remotely. However, protecting the confidentiality of program logic becomes an important security requirement when the remote environment is not trusted.

The control flow of the program code determines the sequence of instructions to be executed and directly reflects the logic of the program. Control flow obfuscation converts the control flow of a program into an incomprehensible form, which can effectively protect the confidentiality of program logic. Control flow obfuscation is a direct method to protect the confidentiality of program logic. However, existing control flow obfuscation work mainly focuses on software-based code obfuscation. There is no code obfuscation scheme that can resist all analysis attacks, and can only be mitigated to a certain extent. The performance overhead introduced by the reverse engineering and analysis of the program and the code obfuscation scheme often does not meet the requirements of high program execution efficiency, and there are limitations in security and performance overhead.

Through the above analysis, the existing problems and defects in the prior art are: the existing control flow obfuscation work mainly focuses on software-based code obfuscation, and there are limitations in security and performance overhead.

The difficulty and significance of solving the above problems and defects are as follows:

(1) Application software is a digital asset. Once released, malicious attackers can crack and reorganize the software through reverse engineering, plagiarize core algorithms or key functions for profit, and control flow obfuscation is the best way to protect user program logic. direct method;

(2) The user uploads the program to the cloud for execution. The cloud environment is untrustworthy, and the user program logic and algorithm face the risk of being stolen. In this scenario, the control flow obfuscation method should take into account both security and time overhead;

(3) The main idea of the present invention is to hide the judgment condition in the branch statement into the control flow matrix, upload the control flow matrix to the trusted private cloud, upload the converted program to the public cloud, and execute the program in the public cloud to When branching statements, condition evaluation is done in the private cloud according to the control flow matrix.

(4) As a trusted space, the private cloud effectively hides the branch statement logic in the program, and can effectively protect the logic confidentiality of the user program. Therefore, the present invention has far-reaching practical significance for solving the limitations of cloud user program security and performance overhead.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the present invention provides a program control flow obfuscation method, system, storage medium, cloud server and application.

The present invention is implemented in this way, a program control flow obfuscation method, the program control flow obfuscation method includes:

The first step is to hide the branch statement, hide the judgment condition of the branch statement in the original program, convert the judgment condition of the branch statement into the first custom function, and obtain the conversion program and the control flow matrix; the control flow matrix includes the judgment condition of the conversion in the original program. The unique identifier in the program, the identifier of the left and right operands of the comparison operator, and the comparison operator;

The second step is to construct and insert a pseudo-branch statement, construct and insert a pseudo-branch statement before the original statement s, and the pseudo-branch statement will eventually flow to s; convert the judgment condition of the pseudo-branch statement into a second custom function to obtain a conversion program and the control flow matrix; the control flow matrix includes the unique identification of the judgment condition of the conversion in the original program, and True or False;

The third step is to construct and insert relational constraint assignment statements, construct and insert constraint assignment statements before the original branch statement b, construct variables that are unreachable by the branch statement b, and perform pairwise randomization on the integer variables in the random list in the branch statement constraint;

The fourth step is to hide the relationship constraint assignment statement, hide the assignment statement in the original program, convert the assignment statement into a third custom function, and obtain the conversion program and the control flow matrix; the control flow matrix includes the converted unique identifier in the original program , the identifier of the assigned operand, and the assignment statement.

Further, the judgment condition of the branch statement in the original program is hidden, and the judgment condition of the branch statement is converted into a first self-defined function; one parameter of the first self-defined function represents a random list of currently converted branch statements, and the other parameter represents the current The unique identification of the converted branch statement in the source program;

The first custom function can be expressed as follows:

cfQuery(L(s), i(s));

Among them, L(s) represents a random list of currently converted branch statements, and i(s) represents the unique identifier of the currently converted branch statement in the source program.

Further, the random list represents a random list formed by all variables in the original program; the variables in the random list include the left and right operands of the comparison operator; the identifiers of the left and right operands of the comparison operator in the control flow matrix point to the random list. Comparison operators have two operands on the left and right.

Further, the control flow matrix M is represented in the form of a tuple:

The first custom function, M={i(s), iop1, iop2, op};

The second custom function, M={i(s), res};

The third custom function, M={i(s), iop1, iop2, op};

Among them, i(s) represents the unique identifier of the converted program statement in the original program, iop1 and iop2 represent the identifiers of the left and right operands of the converted statement in the original program, and op represents the operator of the calculation of the converted program statement in the original program, res represents the evaluation result returned by the judgment condition of the converted pseudo-branch statement, and the unique identifier of the converted program statement in the original program is represented by the line number of the converted program statement in the original program.

Further, a parameter of the second self-defined function represents the random list of the current branch statement, and the other parameter represents the unique identifier of the currently converted branch statement in the source program;

The second custom function is expressed as follows:

cfQuery(L(s), i(s));

Among them, L(s) represents a random list of currently converted branch statements, and i(s) represents the unique identifier of the currently converted branch statement in the source program;

A parameter of the third self-defined function represents the random list of the current assignment statement, and another parameter represents the unique identification of the assignment statement of the current conversion in the source program;

The third custom function represents:

cfQuery(L(s), i(s));

Among them, L(s) represents a random list of currently converted branch statements, and i(s) represents the unique identifier of the currently converted branch statement in the source program.

Another object of the present invention is to provide a program storage medium for receiving user input, and the stored computer program enables the electronic device to execute any one of the claims, including the following steps:

The first step is to hide the branch statement, hide the judgment condition of the branch statement in the original program, convert the judgment condition of the branch statement into the first custom function, and obtain the conversion program and the control flow matrix; the control flow matrix includes the judgment condition of the conversion in the original program. The unique identifier in the program, the identifier of the left and right operands of the comparison operator, and the comparison operator;

The second step is to construct and insert a pseudo-branch statement, construct and insert a pseudo-branch statement before the original statement s, and the pseudo-branch statement will eventually flow to s; convert the judgment condition of the pseudo-branch statement into a second custom function to obtain a conversion program and the control flow matrix; the control flow matrix includes the unique identification of the judgment condition of the conversion in the original program, and True or False;

The third step is to construct and insert relational constraint assignment statements, construct and insert constraint assignment statements before the original branch statement b, construct variables that are unreachable by the branch statement b, and perform pairwise randomization on the integer variables in the random list in the branch statement constraint;

The fourth step is to hide the relationship constraint assignment statement, hide the assignment statement in the original program, convert the assignment statement into a third custom function, and obtain the conversion program and the control flow matrix; the control flow matrix includes the converted unique identifier in the original program , the identifier of the assigned operand, and the assignment statement.

Another object of the present invention is to provide a program control flow obfuscation system for implementing the program control flow obfuscation method. The program control flow obfuscation system includes:

The pseudo-branch statement insertion module is used to construct and insert a pseudo-branch statement before the original statement s. The pseudo-branch statement will eventually flow to s to ensure that the original control flow of the program is not tampered with;

The relationship constraint assignment statement insertion module is used to construct and insert the constraint assignment statement before the original branch statement b, and construct the unreachable variables of the branch statement b to perform pairwise constraints on the integer variables in the random list in the first self-defined function;

The variable hiding module is used to convert and replace the judgment condition of the true and false branch statement and the relationship constraint assignment statement into the control flow query function, and obtain the conversion program and the control flow matrix.

Another object of the present invention is to provide a cloud server equipped with the program control flow obfuscation system.

Another object of the present invention is to provide a control flow obfuscation method in a cloud computing scenario that implements the program control flow obfuscation method, and the control flow obfuscation method in a cloud computing scenario includes:

Step 1: Insert a pseudo-branch statement, construct and insert a pseudo-branch statement before the original statement s, and the pseudo-branch statement will eventually flow to s;

Step 2, inserting a relationship constraint assignment statement, constructing and inserting a constraint assignment statement before the original branch statement b, and constructing unreachable variables of the branch statement b to perform pairwise constraints on the integer variables in the random list in the first self-defined function;

Step 3, variable hiding, converting and replacing the judgment condition of the true and false branch statement and the relationship constraint assignment statement into a control flow query function to obtain a conversion program and a control flow matrix;

Step 4, sending the conversion program and the control flow matrix to the cloud remote computing unit; the conversion program is stored in the untrusted environment of the remote computing unit, and the control flow matrix is stored in a trusted private cloud;

Step 5: Based on the control flow matrix, the conversion program is executed in the remote computing unit, and the converted branch statement and assignment statement are moved to the trusted private cloud for operation, and the private cloud will determine the incoming parameter value based on the variable constraint relationship. Consistency check is performed, and when the variable constraint relationship is satisfied, the data after the evaluation is returned to the remote computing unit.

Another object of the present invention is to provide a control flow obfuscation system in a cloud computing scenario that implements the control flow obfuscation method in a cloud computing scenario. The program control flow obfuscation system in the cloud computing scenario includes:

The pseudo-branch statement insertion module is used to construct and insert pseudo-branch statements before the original statement s. These pseudo-branch statements will eventually flow to s to ensure that the original control flow of the program is not tampered with;

The relationship constraint assignment statement insertion module is used to construct and insert the constraint assignment statement before the original branch statement b, and construct the unreachable variables of the branch statement b to perform pairwise constraints on the integer variables in the random list in the first self-defined function;

The variable hiding module is used to convert and replace the judgment condition of the true and false branch statement and the relationship constraint assignment statement into the control flow query function, and obtain the conversion program and the control flow matrix;

The program sending module is used to send the conversion program and the control flow matrix to the remote computing unit; the conversion program is stored in the untrusted environment of the remote computing unit, and the control flow matrix is stored in the trusted private cloud;

The program execution module is used to execute the conversion program in the remote computing unit based on the control flow matrix, and the converted branch statement and assignment statement are moved to the trusted private cloud for execution. Consistency check is performed on the parameter values of , and when the variable constraint relationship is satisfied, the data after the evaluation is returned to the remote computing unit.

Combined with all the above-mentioned technical solutions, the advantages and positive effects of the present invention are as follows: the present invention combines the program conversion technology, by hiding the judgment conditions in the branch statement in the program, inserting the pseudo branch statement, and using the above sensitive data flow consistent The secure method ensures high control flow confidentiality; avoids the application logic executed in the cloud from being acquired and maliciously tampered with by external attackers.

The invention can hide the variables of each branch statement condition, avoid malicious acquisition and utilization of application program logic by external attackers; insert pseudo branch statements to increase the difficulty for attackers to reconstruct program control flow; insert relational constraint statements and perform data flow Consistency check prevents attackers from actively changing the running process of the program, and collects effective information by purposefully adding new data during the running of the program.

Combined with cloud computing scenarios, the present invention ensures high control flow confidentiality by transforming the condition of each branch statement and moving its evaluation to a trusted private cloud environment.

The experimental platform of the present invention selects the cloud computing platform as shown in Figure 9, and applies for a Hadoop computing cluster composed of five virtual machines, which includes a master node (Master) and four worker nodes (Slave). The computer is installed with Ubuntu14.04 system, 8g memory and 500g hard disk. For CPU-intensive applications, the experimental results are shown in Table 1. From the data in the table, it can be seen that the performance overhead generated by the solution proposed by the present invention is relatively small. In the scheme proposed by Lan et al. to simulate conditional instructions using λ calculus, the average time taken to evaluate each protected condition is 38.19 μs, while the average calculation time of a single cfQuery function in the scheme proposed by the present invention is 8.31 μs. While taking into account the security, the present invention has less time overhead, and can efficiently protect the logic confidentiality of the user program.

Description of drawings

FIG. 1 is a flowchart of a program control flow obfuscation method provided by an embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a program control flow obfuscation system provided by an embodiment of the present invention.

FIG. 3 is a program transformation diagram of a branch statement judgment condition according to an embodiment of the present invention.

FIG. 4 is a program transformation diagram of constructing and inserting a pseudo-branch statement according to an embodiment of the present invention.

FIG. 5 is a program transformation diagram of constructing and inserting a relational constraint assignment statement according to an embodiment of the present invention.

FIG. 6 is a flowchart of a control flow obfuscation method in a cloud computing scenario according to an embodiment of the present invention.

FIG. 7 is an architecture diagram of a control flow obfuscation method in a cloud computing-oriented scenario according to an embodiment of the present invention.

FIG. 8 is a structural diagram of a control flow obfuscation system in a cloud computing-oriented scenario according to an embodiment of the present invention.

In the figure: 1. Pseudo-branch statement insertion module; 2. Relationship constraint assignment statement insertion module; 3. Variable hiding module; 4. Pseudo-branch statement insertion module; 5. Relationship constraint assignment statement insertion module; 6. Variable hiding module; 7 , the program sending module; 8, the program execution module.

FIG. 9 is a schematic diagram of a cloud computing platform according to an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

In view of the problems existing in the prior art, the present invention provides a program control flow obfuscation method, system, storage medium, cloud server and application. The present invention is described in detail below with reference to the accompanying drawings.

As shown in Figure 1, the program control flow obfuscation method provided by the present invention includes the following steps:

S101: construct and insert pseudo-branch statements, construct and insert pseudo-branch statements before the original statement s, and these pseudo-branch statements will eventually flow to s to ensure that the original control flow of the program is not tampered with;

S102: constructing and inserting relational constraint assignment statements, constructing and inserting constraint assignment statements before the original branch statement b, constructing variables that are unreachable by the branch statement b, and performing pairwise random constraints on the variables in the random list in the branch statement;

S103: Hide the branch statement and the relationship constraint assignment statement, hide the branch statement and the relationship constraint assignment statement in the original program, convert them into a control flow query function, and obtain a conversion program and a control flow matrix.

The program control flow obfuscation method provided by the present invention can be implemented on a user host, and the original program can be a program based on a three-address code.

The control flow matrix M can be represented in the form of a tuple as follows:

The first custom function, M={i(s), iop1, iop2, op};

The second custom function, M={i(s), res};

The third custom function, M={i(s), iop1, iop2, op};

Among them, i(s) represents the unique identifier of the converted program statement in the original program, iop1 and iop2 represent the identifiers of the left and right operands of the converted statement in the original program, and op represents the operator of the calculation of the converted program statement in the original program, res represents the evaluation result returned by the judgment condition of the converted pseudo-branch statement. In the present invention, the unique identification of the converted program statement in the original program is represented by the line number of the converted program statement in the original program.

The present invention hides the judgment condition of the branch statement in the original program, and converts the judgment condition of the branch statement into a first self-defined function; one parameter of the first self-defined function represents a random list of currently converted branch statements, and the other parameter represents the current The unique identification of the converted branch statement in the source program.

Specifically, the first custom function can be expressed as follows:

cfQuery(L(s), i(s));

Among them, L(s) represents a random list of currently converted branch statements, and i(s) represents the unique identifier of the currently converted branch statement in the source program. It should be noted that the function name cfQuery only represents an instance, and it can be other function names during specific implementation.

As shown in Figure 2, the program control flow obfuscation system provided by the present invention includes:

The pseudo-branch statement insertion module 1 is used to construct and insert pseudo-branch statements before the original statement s, and these pseudo-branch statements will eventually flow to s to ensure that the original control flow of the program is not tampered with.

The relational constraint assignment statement insertion module 2 is used to construct and insert a constraint assignment statement before the original branch statement b, and construct the unreachable variables of the branch statement b to perform pairwise constraints on the integer variables in the random list in the first self-defined function .

The variable hiding module 3 is used to convert and replace the judgment condition of the true and false branch statement and the relationship constraint assignment statement into a control flow query function, and obtain a conversion program and a control flow matrix.

The technical solutions of the present invention will be further described below with reference to the accompanying drawings.

As shown in FIG. 3 , the original program includes the branch statement if(cfQuery(a, y, b, x), B1) goto L1 for specific description as follows. According to the control flow matrix, where x and y represent the real variables in the judgment condition of the branch statement, the return value of this first custom function is x>y.

Construct and insert pseudo-branch statements, construct and insert pseudo-branch statements before the original statement s, and these pseudo-branch statements will eventually flow to s to ensure that the original control flow of the program is not tampered with; convert the judgment conditions of the pseudo-branch statement to the second Custom function to obtain the conversion program and control flow matrix; the control flow matrix includes the unique identification of the conversion judgment condition in the original program, and True or False; one parameter of the two custom functions represents a random list of current branch statements, and the other The parameter represents the unique identifier of the currently converted branch statement in the source program.

The random list represents a random list formed by all variables in the original program; the variables in the random list include the left and right operands of the comparison operator; the identifiers of the left and right operands of the comparison operator in the control flow matrix point to the left and right of the comparison operator in the random list two operands.

Specifically, the second custom function can be expressed as follows:

cfQuery(L(s), i(s));

Among them, L(s) represents a random list of currently converted branch statements, and i(s) represents the unique identifier of the currently converted branch statement in the source program. It should be noted that the function name cfQuery only represents an instance, and it can be other function names during specific implementation.

As shown in FIG. 4 , the original program includes the branch statement if(cfQuery(a, y, b, x), B2) goto L2 for specific description as follows. According to the control flow matrix, this second custom function returns false.

Construct and insert relational constraint assignment statements, construct and insert constraint assignment statements before the original branch statement b, construct variables that are unreachable by the branch statement b, and perform pairwise random constraints on the integer variables in the random list in the branch statement.

The relationship constraint assignment statement is hidden, the assignment statement in the original program is hidden, the assignment statement is converted into a third custom function, and the conversion program and the control flow matrix are obtained; the control flow matrix includes the unique identifier of the converted original program, and the assigned operation Number identification and assignment statements.

Preferably, one parameter of the third custom function represents a random list of current assignment statements, and another parameter represents the unique identifier of the currently converted assignment statement in the source program.

Specifically, the third custom function can be expressed as follows:

cfQuery(L(s), i(s));

Among them, L(s) represents a random list of currently converted branch statements, and i(s) represents the unique identifier of the currently converted branch statement in the source program. It should be noted that the function name cfQuery only represents an instance, and can be other function names during specific implementation.

As shown in FIG. 5 , the original program includes the branch statement Ins0=cfQuery((a, y, b, x), B3) for specific description as follows. According to the control flow matrix, the return value of this third custom function is x+y.

As shown in FIG. 6 , the control flow obfuscation method for cloud computing scenarios provided by the present invention includes the following steps:

S601: Inserting pseudo-branch statements, constructing and inserting pseudo-branch statements before the original statement s, and these pseudo-branch statements will eventually flow to s to ensure that the original control flow of the program is not tampered with;

S602: Inserting a relationship constraint assignment statement, constructing and inserting a constraint assignment statement before the original branch statement b, and constructing unreachable variables of the branch statement b to perform pairwise constraints on the integer variables in the random list in the first custom function;

S603: Variable hiding, converting and replacing the judgment condition of the true and false branch statement and the relationship constraint assignment statement into a control flow query function to obtain a conversion program and a control flow matrix;

S604: Send the conversion program and the control flow matrix to the cloud remote computing unit; the conversion program is stored in the untrusted environment of the remote computing unit, and the control flow matrix is stored in a trusted private cloud;

S605: Based on the control flow matrix, the conversion program is executed in the remote computing unit, and the converted branch statement and assignment statement are moved to a trusted private cloud for execution, and the input parameter value will be processed in the private cloud based on the variable constraint relationship. Consistency check, when the variable constraint relationship is satisfied, the data after the evaluation is returned to the remote computing unit.

S601 to S603 of the present invention may be implemented on a user host, and the source program may be a program based on a three-address code.

The control flow matrix M can be represented in the form of a tuple as follows:

The first custom function, M={i(s), iop1, iop2, op};

The second custom function, M={i(s), res};

The third custom function, M={i(s), iop1, iop2, op};

Among them, i(s) represents the unique identifier of the converted program statement in the original program, iop1 and iop2 represent the identifiers of the left and right operands of the converted statement in the original program, and op represents the operator of the calculation of the converted program statement in the original program, res represents the evaluation result returned by the judgment condition of the converted pseudo-branch statement. The unique identification of the converted program statement in the original program in the present invention is represented by the line number of the converted program statement in the original program.

As shown in Figure 7, for the original program P that the user wants to execute on the public cloud, it is first converted into a conversion program P' and a control flow matrix M in the user environment. P' differs from P in that the conditional logic of each branch statement is moved into M. After conversion, P' will be uploaded to the cloud host on the public cloud and will be executed in an untrusted area, and the user needs to upload the encrypted control flow matrix M to the trusted private cloud. During the execution of P', the judgment condition in each branch statement and the relational constraint assignment statement will be evaluated in the private cloud based on M.

As shown in FIG. 8 , the program control flow obfuscation system for cloud computing scenarios provided by the present invention includes:

The pseudo-branch statement insertion module 4 is used to construct and insert pseudo-branch statements before the original statement s, and these pseudo-branch statements will eventually flow to s to ensure that the original control flow of the program is not tampered with;

The relationship constraint assignment statement insertion module 5 is used for constructing and inserting a constraint assignment statement before the original branch statement b, and constructing the unreachable variables of the branch statement b to perform pairwise constraints on the integer variables in the random list in the first self-defined function ;

The variable hiding module 6 is used to convert and replace the judgment condition of the true and false branch statement and the relationship constraint assignment statement into a control flow query function to obtain a conversion program and a control flow matrix.

The program sending module 7 is used to send the conversion program and the control flow matrix to the remote computing unit; the conversion program is stored in the untrusted environment of the remote computing unit, and the control flow matrix is stored in a trusted private cloud;

The program execution module 8 is used to execute the conversion program in the remote computing unit based on the control flow matrix, and the converted branch statement and assignment statement are moved to the trusted private cloud to run, and the internal private cloud will transfer the data based on the variable constraint relationship. The input parameter value is checked for consistency, and when the variable constraint relationship is satisfied, the data after the evaluation is returned to the remote computing unit.

The technical effects of the present invention will be described in detail below in conjunction with experiments.

The experimental platform of the present invention selects the cloud computing platform as shown in Figure 9, and applies for a Hadoop computing cluster composed of five virtual machines, which includes a master node (Master) and four worker nodes (Slave). The computer is installed with Ubuntu14.04 system, 8g memory and 500g hard disk. For CPU-intensive applications, the experimental results are shown in Table 1. From the data in the table, it can be seen that the performance overhead generated by the solution proposed by the present invention is relatively small. In the scheme proposed by Lan et al. to simulate conditional instructions using λ calculus, the average time taken to evaluate each protected condition is 38.19 μs, while the average calculation time of a single cfQuery function in the scheme proposed by the present invention is 8.31 μs. While taking into account the security, the present invention has less time overhead, and can efficiently protect the logic confidentiality of the user program.

Table 1 Performance consumption for CPU-intensive programs

It should be noted that the embodiments of the present invention may be implemented by hardware, software, or a combination of software and hardware. The hardware portion may be implemented using special purpose logic; the software portion may be stored in memory and executed by a suitable instruction execution system, such as a microprocessor or specially designed hardware. Those of ordinary skill in the art will appreciate that the apparatus and methods described above may be implemented using computer-executable instructions and/or embodied in processor control code, for example on a carrier medium such as a disk, CD or DVD-ROM, such as a read-only memory Such code is provided on a programmable memory (firmware) or a data carrier such as an optical or electronic signal carrier. The device and its modules of the present invention can be implemented by hardware circuits such as very large scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., It can also be implemented by software executed by various types of processors, or by a combination of the above-mentioned hardware circuits and software, such as firmware.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. Any person skilled in the art is within the technical scope disclosed by the present invention, and all within the spirit and principle of the present invention Any modifications, equivalent replacements and improvements made within the scope of the present invention should be included within the protection scope of the present invention.

Claims (10)

1. a program control flow obfuscation method, is characterized in that, described program control flow obfuscation method comprises: The first step is to hide the branch statement, hide the judgment condition of the branch statement in the original program, convert the judgment condition of the branch statement into the first custom function, and obtain the conversion program and the control flow matrix; the control flow matrix includes the judgment condition of the conversion in the original program. The unique identifier in the program, the identifier of the left and right operands of the comparison operator, and the comparison operator; The second step is to construct and insert a pseudo-branch statement, construct and insert a pseudo-branch statement before the original statement s, and the pseudo-branch statement will eventually flow to s; convert the judgment condition of the pseudo-branch statement into a second custom function to obtain a conversion program and the control flow matrix; the control flow matrix includes the unique identification of the judgment condition of the conversion in the original program, and True or False; The third step is to construct and insert relational constraint assignment statements, construct and insert constraint assignment statements before the original branch statement b, construct variables that are unreachable by the branch statement b, and perform pairwise randomization on the integer variables in the random list in the branch statement constraint; The fourth step is to hide the relationship constraint assignment statement, hide the assignment statement in the original program, convert the assignment statement into a third custom function, and obtain the conversion program and the control flow matrix; the control flow matrix includes the converted unique identifier in the original program , the identifier of the assigned operand, and the assignment statement. 2. The program control flow obfuscation method as claimed in claim 1, wherein the branch statement judgment condition in the original program is hidden, and the judgment condition of the branch statement is converted into a first self-defined function; One parameter represents a random list of currently converted branch statements, and the other parameter represents the unique identifier of the currently converted branch statement in the source program; The first custom function can be expressed as follows: cfQuery(L(s), i(s)); Among them, L(s) represents a random list of currently converted branch statements, and i(s) represents the unique identifier of the currently converted branch statement in the source program. 3. The program control flow obfuscation method as claimed in claim 1, wherein the random list represents a random list formed by all variables in the original program; the variables in the random list include two operands left and right of a comparison operator; control The identifiers of the left and right operands of the comparison operator in the stream matrix point to the left and right operands of the comparison operator in the random list. 4. The program control flow obfuscation method of claim 3, wherein the control flow matrix M is represented in the form of a tuple: The first custom function, M={i(s), iop1, iop2, op}; The second custom function, M={i(s), res}; The third custom function, M={i(s), iop1, iop2, op}; Among them, i(s) represents the unique identifier of the converted program statement in the original program, iop1 and iop2 represent the identifiers of the left and right operands of the converted statement in the original program, and op represents the operator of the calculation of the converted program statement in the original program, res represents the evaluation result returned by the judgment condition of the converted pseudo-branch statement, and the unique identifier of the converted program statement in the original program is represented by the line number of the converted program statement in the original program. 5. The program control flow obfuscation method according to claim 1, wherein a parameter of the second self-defined function represents a random list of current branch statements, and another parameter represents the currently converted branch statement in the source program. Uniquely identifies; The second custom function is expressed as follows: cfQuery(L(s), i(s)); Among them, L(s) represents a random list of currently converted branch statements, and i(s) represents the unique identifier of the currently converted branch statement in the source program; A parameter of the third self-defined function represents the random list of the current assignment statement, and another parameter represents the unique identification of the assignment statement of the current conversion in the source program; The third custom function represents: cfQuery(L(s), i(s)); Among them, L(s) represents a random list of currently converted branch statements, and i(s) represents the unique identifier of the currently converted branch statement in the source program. 6. A program storage medium for receiving user input, the stored computer program causing the electronic device to execute any one of the claims comprising the following steps: The first step is to hide the branch statement, hide the judgment condition of the branch statement in the original program, convert the judgment condition of the branch statement into the first custom function, and obtain the conversion program and the control flow matrix; the control flow matrix includes the judgment condition of the conversion in the original program. The unique identifier in the program, the identifier of the left and right operands of the comparison operator, and the comparison operator; The second step is to construct and insert a pseudo-branch statement, construct and insert a pseudo-branch statement before the original statement s, and the pseudo-branch statement will eventually flow to s; convert the judgment condition of the pseudo-branch statement into a second custom function to obtain a conversion program and the control flow matrix; the control flow matrix includes the unique identification of the judgment condition of the conversion in the original program, and True or False; The third step is to construct and insert relational constraint assignment statements, construct and insert constraint assignment statements before the original branch statement b, construct variables that are unreachable by the branch statement b, and perform pairwise randomization on the integer variables in the random list in the branch statement constraint; The fourth step is to hide the relationship constraint assignment statement, hide the assignment statement in the original program, convert the assignment statement into a third custom function, and obtain the conversion program and the control flow matrix; the control flow matrix includes the converted unique identifier in the original program , the identifier of the assigned operand, and the assignment statement. 7. A program control flow obfuscation system for implementing the program control flow obfuscation method according to any one of claims 1 to 5, wherein the program control flow obfuscation system comprises: The pseudo-branch statement insertion module is used to construct and insert a pseudo-branch statement before the original statement s. The pseudo-branch statement will eventually flow to s to ensure that the original control flow of the program is not tampered with; The relationship constraint assignment statement insertion module is used to construct and insert the constraint assignment statement before the original branch statement b, and construct the unreachable variables of the branch statement b to perform pairwise constraints on the integer variables in the random list in the first self-defined function; The variable hiding module is used to convert the judgment condition of the true and false branch statement and the relationship constraint assignment statement into a control flow query function, and obtain the conversion program and the control flow matrix. 8. A cloud server equipped with the program control flow obfuscation system of claim 7. 9 . A control flow obfuscation method in a cloud computing scenario for implementing the program control flow obfuscation method according to any one of claims 1 to 5, wherein the control flow obfuscation method in a cloud computing scenario comprises: Step 1: Insert a pseudo-branch statement, construct and insert a pseudo-branch statement before the original statement s, and the pseudo-branch statement will eventually flow to s; Step 2, inserting a relationship constraint assignment statement, constructing and inserting a constraint assignment statement before the original branch statement b, and constructing unreachable variables of the branch statement b to perform pairwise constraints on the integer variables in the random list in the first self-defined function; Step 3, variable hiding, converting and replacing the judgment condition of the true and false branch statement and the relationship constraint assignment statement into a control flow query function to obtain a conversion program and a control flow matrix; Step 4, sending the conversion program and the control flow matrix to the cloud remote computing unit; the conversion program is stored in the untrusted environment of the remote computing unit, and the control flow matrix is stored in a trusted private cloud; Step 5: Based on the control flow matrix, the conversion program is executed in the remote computing unit, and the converted branch statement and assignment statement are moved to the trusted private cloud for operation, and the private cloud will determine the incoming parameter value based on the variable constraint relationship. Consistency check is performed, and when the variable constraint relationship is satisfied, the data after the evaluation is returned to the remote computing unit. 10. A control flow obfuscation system in a cloud computing scenario for implementing the control flow obfuscation method in a cloud computing scenario according to claim 9, wherein the program control flow obfuscation system in the cloud computing scenario comprises: : The pseudo-branch statement insertion module is used to construct and insert pseudo-branch statements before the original statement s. These pseudo-branch statements will eventually flow to s to ensure that the original control flow of the program is not tampered with; The relationship constraint assignment statement insertion module is used to construct and insert the constraint assignment statement before the original branch statement b, and construct the unreachable variables of the branch statement b to perform pairwise constraints on the integer variables in the random list in the first self-defined function; The variable hiding module is used to convert and replace the judgment condition of the true and false branch statement and the relationship constraint assignment statement into the control flow query function, and obtain the conversion program and the control flow matrix; The program sending module is used to send the conversion program and the control flow matrix to the remote computing unit; the conversion program is stored in the untrusted environment of the remote computing unit, and the control flow matrix is stored in the trusted private cloud; The program execution module is used to execute the conversion program in the remote computing unit based on the control flow matrix, and the converted branch statement and assignment statement are moved to the trusted private cloud for execution. Consistency check is performed on the parameter values of , and when the variable constraint relationship is satisfied, the data after the evaluation is returned to the remote computing unit.

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