KR101408388B1 - Watermarking apparatus and method for protecting software property right - Google Patents

Abstract

Disclosed are a watermarking device and a method to protect software copyright. The disclosed watermarking device includes: a bit line generating part generating a bit line used as a watermark; a dependent graph generating part generating two or more dependent graphs by reallocating the execution command orders based on a dependent relationship established between the partial commands of the commands in regard to a basic block forming an execution code of the software including the commands; and a basic block transforming part transforming the basic block by selecting a dependent graph of a turn corresponding to the generating bit line among the dependent graphs, and reallocating the execution order of the commands in the basic block. The turn of the selected dependent graph is used as the watermark.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a watermarking apparatus and a watermarking apparatus,

Embodiments of the present invention are directed to a watermarking apparatus and method for software copyright protection.

Software watermarking technology is a technology for inserting and extracting specific information (watermark) invisibly without changing the function of the original program, with respect to the source code or executable code of the program. A software watermarking device or software can be divided into an inserter for inserting information into the original program and an extractor for extracting original information from the program.

On the other hand, the watermarking technique can be generally divided into two types, static watermarking and dynamic watermarking. Dynamic watermarking is a method of inserting and extracting information through a state during program execution. Static watermarking is a method of inserting and extracting information by analyzing code of a program executable file without executing a program.

The evaluation factors of software watermarking technology can be divided into robustness, resilience, stealthness, data-rate, and efficiency. Robustness indicates how easily it is destroyed or analyzed by attack through obfuscation, optimization, reverse engineering, etc. Data rate shows how much information can be inserted into the program. Efficiency shows the code size of the program after execution and execution time And how much it increases.

Generally, the dynamic watermarking method has high robustness, but its efficiency is very low and practicality is lowered. Actually, a static watermarking method is used in many cases. However, the static watermarking method has high efficiency, but is easily destroyed through code modification such as obfuscation and optimization.

It is an object of the present invention to provide a watermarking apparatus and method using a resilience and reliable watermarking technique capable of error-correction.

Another object of the present invention is to provide a watermarking apparatus capable of inserting a watermark which does not affect the program code, the size of the program, and the execution speed of the program.

To achieve the above object, according to a preferred embodiment of the present invention, there is provided a watermarking apparatus for copyright protection of software, comprising: a bit stream generating unit for generating a bit stream used as a watermark; For a basic block comprising executable code of the software and comprising a plurality of instructions, relocating the execution order of the instructions based on a dependency relationship established between instructions of at least some of the instructions, A dependency graph generating unit for generating a dependency graph; Selecting a dependency graph of the sequence number corresponding to the generated bit stream from among the two or more dependency graphs and rearranging the execution order of the instructions in the basic block according to the execution order of the instructions in the selected dependency graph, Wherein a number of the selected dependency graph is used as the watermark, wherein the number of the selected dependency graph is used as the watermark.

The number of the generated basic bit blocks and the number of the basic blocks to be generated may be n (an integer of 2 or more).

The bitstream generator may generate the n bitstreams using the extended bitstream by expanding each of the plurality of bits constituting the original bitstream to generate an extended bitstream larger than the original bitstream.

The bitstream generator may extend each of the plurality of bits using a gray code.

Wherein the bit string generating unit decomposes the number corresponding to the extended bit string into n algebraic joint expressions based on the remaining theorems of the Chinese and generates the n bits using the remaining digits included in each of the n algebraic joint expressions, Columns.

The watermarking apparatus includes a dummy instruction insertion unit for generating a dependency relation between the instructions of some of the plurality of instructions and one or more dummy instructions and inserting the one or more dummy instructions into the basic block in accordance with the generated dependency relation, And < / RTI >

According to another embodiment of the present invention, there is provided a watermarking method for copyright protection of software, comprising the steps of: generating a bit stream to be used as a watermark; For a basic block comprising executable code of the software and comprising a plurality of instructions, relocating the execution order of the instructions based on a dependency relationship established between instructions of at least some of the instructions, ; Selecting a dependency graph of the sequence number corresponding to the generated bit stream from among the two or more dependency graphs and rearranging the execution order of the instructions in the basic block according to the execution order of the instructions in the selected dependency graph, Wherein the order of the selected dependency graph is used as the watermark, and a method of watermarking for copyright protection of software is provided.

According to the present invention, even if a part of the watermark is damaged, the watermark can be easily recovered through an error correction technique.

In addition, according to the present invention, watermarking is performed in the form of steganography, which does not affect the target program code and does not increase the size of the program and does not lower the program execution speed.

In addition, according to the present invention, watermarking is performed in staganographic form, which has the advantage of minimizing the time required for watermarking.

Further, according to the present invention, since the performance of watermarking is independent of the program logic, there is an advantage that watermarks embedded in code optimization and code obfuscation attacks are not easily modulated.

1 is a diagram showing a schematic configuration of a watermarking apparatus for copyright protection of software according to an embodiment of the present invention.
2 is a diagram showing a schematic configuration of a watermarking method for copyright protection of software according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating a detailed procedure of an operation (bit stream generation process) of the bit stream generation unit according to an embodiment of the present invention.
4 is a diagram illustrating an example of a dependency graph according to an embodiment of the present invention.
5 is a diagram illustrating a concept of inserting a dummy instruction in accordance with an embodiment of the present invention.
6 is a diagram illustrating an example of an Android framework for performing watermarking according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram showing a schematic configuration of a watermarking apparatus for copyright protection of software according to an embodiment of the present invention.

Referring to FIG. 1, a watermarking apparatus 100 according to an embodiment of the present invention includes a bit stream generating unit 110, a dependency graph generating unit 120, a basic block transforming unit 130, 140).

2 is a diagram showing a schematic configuration of a watermarking method for copyright protection of software according to an embodiment of the present invention.

Hereinafter, the function of each component and the process performed in each step will be described in detail with reference to FIG. 1 and FIG.

First, in step S210, the bit stream generation unit 110 generates a bit stream to be used as a watermark. At this time, the number of bit strings used as a watermark may be n (an integer of 2 or more).

FIG. 3 is a diagram illustrating a detailed process of an operation (bit stream generating process) of the bit stream generating unit 110 according to an embodiment of the present invention. Hereinafter, the detailed procedure of step S210 will be described in detail with reference to FIG.

In step S211, the first bit string for the watermark is encrypted. In step S212, the encrypted bit string is divided into a predetermined size. In step S213, each of the plurality of bits constituting the original bit string is extended to one divided bit string (hereinafter referred to as "one bit string"), .

According to an embodiment of the present invention, in step S213, the bitstream generation unit 110 may generate an extended bitstream by extending each of a plurality of bits constituting an original bitstream using gray codes .

As an example, when the original bit string is composed of six bits 010011 and the gray code is composed of three bit strings (000, 001, 011, 010, 110, 111, 101, 100) The column generating unit 110 may randomly select any one of four gray codes having the same MSB as each bit of the original bit string and generate an extended bit string by replacing each bit with each bit. For example, the original bit string 010011 can be extended to the extended bit string (001110010011111101).

Subsequently, in step S214, n bit strings are generated using the extended bit string.

According to an embodiment of the present invention, in step S214, the bitstream generation unit 110 may generate n bitstreams based on the rest of the Chinese theorem.

More specifically, the bitstream generator 110 decomposes the number corresponding to the extended bitstream into n algebraic joints, generates n bitstreams using the remaining digits contained in each of the n algebraic joints can do.

The Chinese Reminder Theorem (CRT) means that "p ₁ to p _r are natural numbers of r numbers that are relatively small, and b ₁ to b _r are natural numbers of r ratios, The r algebraic equations for a particular integer (W) have a unique solution with respect to the law p ₁ to the law p _r .

Where p ₁ to p _r are the quotient of the algebraic combination, and b ₁ to b _r are the remainder of the algebraic combination.

Meanwhile, according to an embodiment of the present invention, the bitstream generator 110 may generate n bitstreams from an original bitstream using the generalized Chinese generalized CRT. In this case, each of the n algebraic joint expressions may be expressed as Equation (2) below, and the n bit strings may be a binary number corresponding to the remaining digits of each algebraic joint expression.

Here, W is a number corresponding to the original bit string, x _k is the remaining number of the kth algebraic combination (that is, k-th bit stream), p _ik and p _jk are the numbers of r natural numbers p ₁ to p _r It means two natural numbers for constructing the quotient of the kth algebraic conjunction. As an example, in the case of the first joint simultaneous expression p _ik and p _jk is a p ₁ and p ₂ may be, in the case of the second joint simultaneous expression p _{ik jk} and p each may be p ₁ and p _3.

)개이다. 또한, 원 비트열과 대응되는 숫자는 r개의 서로소인 자연수의 곱 보다 작은 것으로 가정한다. The number of the above-mentioned simultaneous equations is _r C ₂ (=

). In addition, it is assumed that the number corresponding to the original bit string is smaller than the product of r natural numbers of two numbers.

Also, according to another embodiment of the present invention, the bit stream generator 110 may generate n bit streams by modifying the remaining digits derived from Equation (2). That is, the bit stream generator 110 can generate n bit streams using Equation (3) below.

Here, w _k denotes a k-th bit stream.

For example, in the case where the number corresponding to the original bit string is 17, and the three independent natural numbers are 2, 3, and 5, the bit string generator generates three bit strings w1, w2, w3 < / RTI >

As described above, the bitstream generation unit 110 according to an embodiment of the present invention generates n bit strings to be used as a watermark by using the rest of the Chinese theorems, so that even if a part of the watermark is corrupted, There is an advantage of recovering the watermark.

Referring again to FIG. 2, a watermarking method for copyright protection of software according to an embodiment of the present invention will be described in detail.

In step S220, the dependency graph generation unit 120 constitutes executable code of the software and, for a basic block including a plurality of instructions, generates a dependency graph based on a dependency relationship established between at least some of the instructions. To generate two or more dependency graphs. The generation of such dependency graphs is performed for each of the n basic blocks.

Here, the dependency of the instruction means the precedence relation of execution of the instruction. For example, if command A must be performed after command B has been executed, then command A and command B have dependencies. The generation of such dependency graphs is performed for each of the n basic blocks.

As an example, when the number of instructions (nodes) included in a specific basic block is seven and a dependency relationship as shown in FIG. 4A is established between seven instructions, the dependency graph generator 120 may generate the dependency graph shown in Figs. 4 (b) to 4 (d), and may further generate one or more dependency graphs.

Referring to FIG. 4, node 7 is necessarily located after node 3, and node 3 must be located after node 1 and node 2. In addition, node 6 must be located after node 5. And, except for this relationship, each node can be in various locations, and thus two or more dependency graphs can be generated.

Then, in step S230, the basic block transforming unit 130 selects a dependency graph of the sequence corresponding to the bit string generated by the bit sequence generator 110 from among the two or more dependency graphs, Rearranges the execution order of the instructions in the basic block according to the order of execution of the instructions of the basic block. This modification of the basic block is performed for each of the n basic blocks.

As an example, if the number corresponding to the k-th bit stream is 12, the basic block transformer 130 selects the 12-th dependency graph among the 2 or more dependency graphs for the k-th basic block, According to the execution order of the instructions, the execution order of the instructions included in the k-th basic block is rearranged to transform the k-th basic block.

Accordingly, the order of the selected dependency graph (i.e., number 12) can be used as a watermark for the software. That is, if it is desired to extract a watermark at a later time, the system checks whether the order of the instructions included in each of the n basic blocks is the same as the order of execution of the instructions in the selected dependency graph, Is confirmed with the inserted normal software.

Next, in step S240, the dummy instruction insertion section 140 generates a dependency relation between the instructions of some of the plurality of instructions included in the basic block and one or more dummy instructions, Insert one or more dummy instructions into the basic block. This insertion of the dummy instruction is also performed for each of the n basic blocks.

Here, the dummy instruction means an instruction which does not affect the execution according to the instructions in the basic block. For example, the dummy instruction may be a command that adds a value of 1 to a specific bit and subtracts a value of 1 (i.e., the specific bit value does not change by the execution of the dummy instruction).

5 is a diagram showing a concept of inserting a dummy command. Referring to FIG. 5, the dummy instruction insertion unit 140 may set a dependency relation between the dummy instruction E1 and the instruction word 5, the instruction word 2 and the instruction word 6 as shown in FIG. 5A. In this case, if the dependency graph selected for the corresponding basic block is as shown in FIG. 5B, the dummy command inserter 140 inserts the dependency graph in accordance with the dependency of newly determined dummy commands as shown in FIG. 5C , The corresponding dummy instructions can be inserted into the basic block.

In this case, the position where the dummy command is inserted may be the position where the number of cases in which the position of the dummy command can be changed after the dummy command is inserted is the smallest number. For example, in FIG. 5C, the dummy command E1 can not exist at a different position except for the corresponding position due to the dependency relation between the command 5 and the command 2. The dummy command E2 is also the command 3, the command 7, Due to the dependency relationship between command 4 and command 6, it can not exist at other positions except the corresponding position.

When the dummy command is inserted and the watermark is to be extracted later, the system checks the position of the dummy command inserted in each of the n basic blocks and determines whether the position of each dummy command is the same as the first inserted position And if it is the same, it is confirmed by the normal software in which the watermark is inserted.

On the other hand, there may occur a case where the position of the dummy command is arbitrarily changed in order to remove the embedded watermark for illegal copying. In this case, due to the dependency relationship selected for the dummy instructions, if the position of the dummy instruction is changed, the corresponding basic block may not be executed, thereby blocking the execution of the illegally copied software After the dummy command is inserted, the dummy command is inserted at the position where the position of the dummy command can be changed most.

As described above, according to the present invention, watermarking is performed in the form of steganography, which does not affect the program code of the target software, does not increase the size of the program, does not deteriorate the program execution speed, There is an advantage that the execution time of the watermarking can be minimized. In addition, since the performance of watermarking is independent of the program logic, there is an advantage that watermark embedded in code optimization and code obfuscation attacks can not be easily modulated.

6 is a diagram illustrating an example of an Android framework for performing watermarking according to an embodiment of the present invention.

The Android framework shown in FIG. 6 is implemented based on a low-power watermarking framework (hereinafter referred to as a framework). The Android framework abstracts the structure of an Android application executable file and provides an API to efficiently apply and test a watermarking algorithm. The environment can be configured.

Referring to FIG. 6, the Android framework includes a core component for manipulating an application executable file, a utility for assisting the component, a UI component for managing user input / output, and a library for APK packaging.

The core component consists of a Dex parser for analyzing the file structure, a Watermarking Engine for inserting a message, and a Dex rebuilder for reconstructing a Dex file. The UI component includes a graph for the main task of the framework, As shown in FIG.

The process of performing watermarking through the Android framework includes parsing and structure analysis of the app executable file, inserting watermark and forensic mark, and reconstructing the app executable file. In the parsing step, the Dex file is extracted from the APK file, and the types and characteristics of each component are analyzed and the instruction is parsed.

Embodiments of the present invention may be implemented in the form of program instructions that can be executed on various computer means and recorded on a computer readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Examples of program instructions, such as magneto-optical and ROM, RAM, flash memory and the like, can be executed by a computer using an interpreter or the like, as well as machine code, Includes a high-level language code. The hardware devices described above may be configured to operate as one or more software modules to perform operations of one embodiment of the present invention, and vice versa.

As described above, the present invention has been described with reference to particular embodiments, such as specific elements, and limited embodiments and drawings. However, it should be understood that the present invention is not limited to the above- Various modifications and variations may be made thereto by those skilled in the art to which the present invention pertains. Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (7)

A watermarking apparatus for copyright protection of software including a plurality of basic blocks,
A bit stream generating unit for generating a bit stream used as a watermark;
Rearranging the execution order of the instructions based on the dependency relation established between at least some of the plurality of instructions included in the corresponding basic block for the basic block corresponding to the generated bit string, A dependency graph generation unit for generating dependency graphs; And
Selecting dependency graphs of the same sequence number as the number of the generated bitstreams from the two or more dependency graphs and rearranging the execution order of the instructions in the corresponding basic block according to the order of execution of the instructions in the selected dependency graph, And a basic block transformer for transforming the corresponding basic block,
And the order of the selected dependency graph is used as the watermark. The method according to claim 1,
Wherein the number of the generated basic bit blocks and the number of the basic blocks to be modified are n (an integer of 2 or more). 3. The method of claim 2,
Wherein the bitstream generator generates each of the plurality of bits constituting the original bitstream to generate an extended bitstream larger than the original bitstream and generates the n bitstreams using the extended bitstream, A watermarking device for copyright protection of software. The method of claim 3,
Wherein the bit string generating unit expands each of the plurality of bits using a gray code. The method of claim 3,
Wherein the bit string generating unit decomposes the number corresponding to the extended bit string into n algebraic joint expressions based on the remaining theorems of the Chinese and generates the n bits using the remaining digits included in each of the n algebraic joint expressions, Wherein the watermarking unit generates the watermarked watermarked watermark. The method according to claim 1,
The watermarking apparatus
A dummy instruction word inserter for generating a dependency relation between the instructions of the plurality of instructions and one or more dummy instruction words and inserting the one or more dummy instruction words into the corresponding basic block according to the generated dependency relation Wherein the watermarking apparatus further comprises a watermarking apparatus for copyright protection of the software. A watermarking method for copyright protection of software including a plurality of basic blocks,
Generating a bit stream to be used as a watermark;
Rearranging the execution order of the instructions based on the dependency relation established between at least some of the plurality of instructions included in the corresponding basic block for the basic block corresponding to the generated bit string, Generating dependency graphs;
Selecting a dependency graph having the same sequence number as the number of the generated bit strings among the two or more dependency graphs and rearranging the execution order of the instructions in the corresponding basic block according to the execution order of the instructions in the selected dependency graph, Modifying a corresponding basic block,
And the order of the selected dependency graph is used as the watermark.

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