JP5477994B2 - Self-rewriting processing device, self-rewriting processing method, and program - Google Patents

Description

  The present invention relates to a self-rewriting processing device, a self-rewriting processing method, and a program.

  Conventionally, a method for making it difficult to analyze and falsify a protection target program has been proposed (see, for example, Patent Document 1). Patent Document 1 discloses a self-rewriting technique as a technique for making it difficult to analyze and falsify a program to be protected.

  In the self-rewriting of Patent Document 1, first, an instruction described in a protection target program is disguised with a fake instruction. Next, a first process for replacing the fake instruction with the original instruction is inserted in front of the fake instruction, and the original instruction replaced by the execution of the first process is inserted behind the fake instruction. Insert a second process that replaces with a fake instruction.

  For this reason, when the protection target program that has been self-rewritten in Patent Document 1 is executed, the first process is executed before the fake instruction is executed. For this reason, it is executed in a state where the fake instruction is restored. In addition, the second process is executed after the fake instruction is executed in a state in which it is restored. For this reason, the instruction which returned to the original will be camouflaged again. Therefore, the camouflaged instruction returns to the original instruction only in a predetermined period before and after execution, and is in a camouflaged state in other periods, so that it is difficult to analyze and falsify the protection target program.

Japanese Patent Laid-Open No. 2004-192068

  In the protection target program in which self-rewriting is performed in Patent Document 1, the original instruction is described in the protection target program in order to execute the first process. For this reason, it is easy to guess what kind of replacement will be performed, and the difficulty of analyzing and falsifying the protection target program cannot be improved.

  Therefore, a method is conceivable in which the original instruction described in the protection target program is encrypted in advance and decrypted when the fake fake instruction is restored. However, in this encryption method, it is necessary to describe the description of the key used for encryption in the protection target program. For this reason, the key is easily leaked, and the difficulty of analyzing and falsifying the program to be protected cannot be improved.

  Therefore, the present invention has been made in view of the above-described problems, and provides a self-rewriting processing device, a self-rewriting processing method, and a program capable of improving the difficulty of analyzing and falsifying a protection target program. With the goal.

  The present invention proposes the following matters in order to solve the above problems.

  (1) The present invention provides a storage means for storing a protection target program (for example, equivalent to the cache 20 in FIG. 1) and a selection means for selecting at least one instruction described in the protection target program (for example, FIG. 1), an instruction encryption means for encrypting the instruction selected by the selection means using a key (for example, equivalent to the CPU 10 in FIG. 1), and the instruction encryption means. Key disguising means (for example, equivalent to the CPU 10 in FIG. 1) for replacing the key with a dummy key, and key restoration processing (for example, FIG. 5) for replacing the dummy key replaced by the key disguising means with the original key. A key restoration process insertion unit (e.g., equivalent to the CPU 10 in FIG. 1) and a command encrypted by the command encryption unit. Instruction decryption process insertion means (for example, instruction decryption process insertion means (for example, equivalent to the instruction decryption process 52A in FIG. 5) for decrypting using the original key replaced by execution of the key recording restoration process (for example, equivalent to the instruction decryption process 52A in FIG. 5) 1) and a key impersonation process (for example, equivalent to the key impersonation process 56 of FIG. 5) for replacing the original key replaced by the execution of the key recovery process with a dummy key. Key impersonation processing insertion means (for example, equivalent to the CPU 10 in FIG. 1) to be inserted into the target program, and instruction impersonation means (for example, equivalent to the CPU 10 in FIG. 1) for replacing the instruction selected by the selection means with a dummy instruction And an instruction restoration process (for example, the instruction restoration process 53 in FIG. 5) which replaces the dummy instruction replaced by the instruction disguising means with the original instruction decoded by the execution of the instruction decoding process. Instruction restoration processing insertion means (for example, equivalent to the CPU 10 in FIG. 1) for inserting the above into the protection target program, and an instruction disguise for replacing the original instruction replaced by execution of the instruction restoration processing with a dummy instruction A self-rewriting process comprising: an instruction impersonation process insertion means (for example, equivalent to the CPU 10 of FIG. 1) for inserting a process (for example, equivalent to the instruction impersonation process 54 of FIG. 5) into the protection target program A device is proposed.

  According to this invention, the self-rewriting processing device includes a storage means, a selection means, an instruction encryption means, a key impersonation means, a key restoration process insertion means, an instruction decryption process insertion means, a key impersonation processing insertion means, an instruction impersonation means, an instruction A restoration processing insertion means and an instruction spoofing processing insertion means are provided. Then, the storage target program is stored by the storage means. Further, at least one instruction described in the protection target program is selected by the selection means. In addition, the instruction encryption means encrypts the instruction selected by the selection means using a key. In addition, the key used by the instruction encryption unit is replaced with a dummy key by the key disguise unit. In addition, the key restoration processing insertion means inserts the key restoration processing into the protection target program. Here, the key restoration process is a process of replacing the dummy key replaced by the key disguising unit with the original key. Further, the instruction decoding process insertion means inserts the instruction decoding process into the protection target program. Here, the instruction decryption process is a process of decrypting the instruction encrypted by the instruction encryption unit using the original key replaced by the execution of the key recovery process. Further, the key impersonation process insertion means inserts the key impersonation process into the protection target program. Here, the key impersonation process is a process of replacing the original key replaced by the execution of the key restoration process with a dummy key. Further, the instruction disguised means replaces the instruction selected by the selecting means with a dummy instruction. Further, the instruction restoration processing insertion means inserts the instruction restoration processing into the protection target program. Here, the instruction restoration process is a process of replacing the dummy instruction replaced by the instruction disguising unit with the original instruction decoded by executing the instruction decoding process. Further, the instruction impersonation process insertion means inserts the instruction impersonation process into the protection target program. Here, the instruction disguise process is a process of replacing the original instruction replaced by the execution of the instruction restoration process with a dummy instruction.

  For this reason, the self-rewrite processing device replaces the instruction described in the protection target program with a dummy instruction by the instruction disguise means, and encrypts the original instruction by the instruction encryption means. According to this, the original instruction of the instruction disguised as a dummy is in an encrypted state.

  Further, the self-rewriting processing apparatus pre-disguises the key used when encrypting the instruction by the instruction encrypting means into a dummy key by the key disguising means by the key disguise process.

  According to the above, the self-rewriting processing device encrypts the original instruction of the dummy disguised instruction and impersonates the key used for encryption, thereby improving the difficulty of analyzing and falsifying the protection target program Can do.

  (2) The present invention relates to the self-rewriting processing device according to (1), wherein the instruction decoding process inserting means replaces the instruction decoding process with a dummy instruction (replaced by the instruction impersonating means in the protection target program). For example, the instruction restoration processing insertion means inserts the instruction restoration processing into the instruction decoding processing (for example, FIG. 5) of the protection target program. 5 and the dummy instruction replaced by the instruction disguising means (for example, equivalent to the dummy first instruction set 51A of FIG. 5), and the instruction disguising process The inserting unit replaces the instruction impersonation process with a dummy instruction (for example, the dummy first instruction set 51 of FIG. 5) replaced by the instruction impersonating unit in the protection target program. The key restoration processing inserting means inserts the key restoration processing ahead of the instruction decoding processing (for example, equivalent to the instruction decoding processing 52A in FIG. 5) in the protection target program. The key impersonation process insertion means inserts the key impersonation process behind the instruction decryption process (for example, equivalent to the instruction decryption process 52A in FIG. 5) in the protection target program. A rewrite processing device is proposed.

  According to the present invention, in the self-rewriting processing device of (1), the instruction decoding process inserting means inserts the instruction decoding process ahead of the dummy instruction replaced by the instruction disguise means in the protection target program. It was. Further, the instruction restoration processing insertion means inserts the instruction restoration processing between the instruction decoding process and the dummy instruction replaced by the instruction disguise means in the protection target program. Further, the instruction impersonation process insertion means inserts the instruction impersonation process behind the dummy instruction replaced by the instruction impersonation means in the protection target program. Further, the key restoration processing insertion means inserts the key restoration processing ahead of the instruction decryption processing in the protection target program. Further, the key impersonation process insertion means inserts the key impersonation process behind the instruction decryption process in the protection target program.

  For this reason, when the protection target program after the above-described processing is performed by the self-rewriting processing device is executed, first, the key restoration processing is executed, and the forged key is restored. Next, an instruction decryption process is executed, and the instruction is decrypted using the restored key. Next, the key impersonation process is executed, the key used for decryption is impersonated again, and the instruction restoration process is executed, so that the instruction that has been impersonated returns to the decrypted instruction. Next, after this instruction is executed, an instruction impersonation process is executed, and this instruction is impersonated again. According to this, an effect similar to the effect mentioned above can be produced.

  (3) The present invention relates to the self-rewriting processing device of (1) or (2), selection by the selection means, encryption by the instruction encryption means, replacement by the key impersonation means, and the key restoration processing. Insertion by insertion means, insertion by the instruction decryption processing insertion means, insertion by the key impersonation processing insertion means, replacement by the instruction impersonation means, insertion by the instruction restoration processing insertion means, and instruction impersonation processing insertion means The self-rewrite processing device is characterized by repeating the insertion by the predetermined number of times (for example, corresponding to the number of repetitions N in FIGS. 2 and 3).

  According to the present invention, selection by the selection means, encryption by the instruction encryption means, replacement by the key impersonation means, insertion by the key restoration processing insertion means, insertion by the instruction decryption processing insertion means, and key impersonation processing insertion The insertion by the means, the replacement by the instruction impersonation means, the insertion by the instruction restoration processing insertion means, and the insertion by the instruction impersonation processing insertion means are repeated a predetermined number of times.

  For this reason, by setting a value of 1 or more as the above-mentioned predetermined number of times, encryption of the original instruction of the dummy disguised instruction and disguise of the key used for encryption are performed a plurality of times. It is possible to further improve the difficulty of analyzing and falsifying the program to be protected.

(4) The present invention includes selection means (for example, equivalent to the CPU 10 in FIG. 1), instruction encryption means (for example, equivalent to the CPU 10 in FIG. 1), key impersonation means (for example, equivalent to the CPU 10 in FIG. 1), key Restoration processing insertion means (for example, equivalent to CPU 10 in FIG. 1), instruction decryption processing insertion means (for example, equivalent to CPU 10 in FIG. 1), key impersonation processing insertion means (for example, equivalent to CPU 10 in FIG. 1), instruction impersonation means (For example, equivalent to the CPU 10 in FIG. 1), instruction restoration processing insertion means (for example, equivalent to the CPU 10 in FIG. 1), and instruction impersonation processing insertion means (for example, equivalent to the CPU 10 in FIG. 1). A self-rewriting processing method, wherein the selection means selects at least one instruction described in the protection target program (for example, step S in FIG. 2). 6 and corresponding to step S22 in FIG. 3) and a second step in which the instruction encryption means encrypts the instruction selected in the first step using a key (for example, corresponding to step S23 in FIG. 3). When the key disguise means, the key used in the second step, a third step of replacing the dummy key (e.g., corresponding to step S30 of FIG. 3) and, said key recovery process inserting means, said first A fourth step (for example, the step in FIG. 3) for inserting a key restoration process (for example, equivalent to the key restoration process 55 in FIG. 5) into which the dummy key replaced in the three steps is replaced with the original key. and equivalent) in S31, the instruction decoding insertion means, the instruction that was encrypted in the second step, the instruction decoding processing for decoding using the original key, which is substituted by the execution of the key recovery process (E.g., corresponding to the instruction decoding process 52A of FIG. 5), a fifth step of inserting into the protected program (e.g., corresponding to step S26 in step S7 and 3 in FIG. 2), the key disguise process inserting means A sixth step of inserting into the protection target program a key impersonation process (for example, equivalent to the key impersonation process 56 of FIG. 5) for replacing the original key replaced by the execution of the key restoration process with a dummy key. (For example, corresponding to step S32 in FIG. 3), and a seventh step (for example, corresponding to step S25 in FIG. 3) in which the instruction disguise means replaces the instruction selected in the first step with a dummy instruction; the instruction restoring process insertion means, the dummy instruction has been substituted in the seventh step, the instruction restoration process of replacing the instruction decoding original instruction decoded by the execution of the ( Eg to the corresponding) to the instruction recovery process 53 of Figure 5, the eighth step of inserting into the protected program (e.g., corresponding to step S27 in FIG. 3), said instruction disguise process insertion means, of the instruction restoration process Ninth step (for example, step of FIG. 3) of inserting into the protection target program an instruction forgery process (for example, equivalent to the instruction forgery process 54 of FIG. 5) that replaces the original instruction replaced by execution with a dummy instruction. Equivalent to S28) is proposed.

  According to the present invention, at least one instruction described in the protection target program is selected. Then, the selected instruction is encrypted using a key, and this key is replaced with a dummy key. Then, a key restoration process that replaces the dummy key with the original key, an instruction decryption process that decrypts the encrypted instruction using the original key replaced by the execution of the key restoration process, and an execution of the key restoration process A key impersonation process for replacing the replaced original key with a dummy key is inserted into the protection target program. Further, the instruction selected above is replaced with a dummy instruction, the instruction restoration process for replacing the dummy instruction with the original instruction decoded by execution of the instruction decoding process, and the original instruction replaced by execution of the instruction restoration process Instruction impersonation processing for replacing an instruction with a dummy instruction is inserted into the protection target program. According to the above, an effect similar to the effect described above can be achieved.

  (5) The present invention selects a first step (for example, corresponding to step S6 in FIG. 2 and step S22 in FIG. 3) for selecting at least one instruction described in the protection target program, and selection in the first step. A second step (for example, corresponding to step S23 in FIG. 3) of encrypting the instruction using a key, and a third step (for example, FIG. 3) replacing the key used in the second step with a dummy key. 3) and a key restoration process (for example, equivalent to the key restoration process 55 in FIG. 5) for replacing the dummy key replaced in the third step with the original key is inserted into the protection target program. The fourth step (e.g., corresponding to step S31 in FIG. 3) and the original key replaced by executing the key recovery process with the instruction encrypted in the second step. And a fifth step (for example, corresponding to step S7 in FIG. 2 and step S26 in FIG. 3) for inserting an instruction decoding process (for example, corresponding to the instruction decoding process 52A in FIG. 5) into the protection target program; A sixth step (for example, inserting a key impersonation process (for example, equivalent to the key impersonation process 56 in FIG. 5) into the protection target program, which replaces the original key replaced by the execution of the key restoration process with a dummy key. , Corresponding to step S32 in FIG. 3), a seventh step (for example, corresponding to step S25 in FIG. 3) replacing the instruction selected in the first step with a dummy instruction, and a dummy replacing in the seventh step Is replaced with the original instruction decoded by the execution of the instruction decoding process (for example, equivalent to the instruction restoration process 53 of FIG. 5). An eighth step (for example, corresponding to step S27 in FIG. 3) to be inserted into the elephant program, and an instruction impersonation process (for example, in FIG. 5) that replaces the original instruction replaced by execution of the instruction restoration process with a dummy instruction. A program for causing a computer to execute a ninth step (for example, corresponding to step S28 in FIG. 3) of inserting a command forgery process 54 into the protection target program is proposed.

  According to the present invention, at least one instruction described in the protection target program is selected by causing the computer to execute the program. Then, the selected instruction is encrypted using a key, and this key is replaced with a dummy key. Then, a key restoration process that replaces the dummy key with the original key, an instruction decryption process that decrypts the encrypted instruction using the original key replaced by the execution of the key restoration process, and an execution of the key restoration process A key impersonation process for replacing the replaced original key with a dummy key is inserted into the protection target program. Further, the instruction selected above is replaced with a dummy instruction, the instruction restoration process for replacing the dummy instruction with the original instruction decoded by execution of the instruction decoding process, and the original instruction replaced by execution of the instruction restoration process Instruction impersonation processing for replacing an instruction with a dummy instruction is inserted into the protection target program. According to the above, an effect similar to the effect described above can be achieved.

  According to the present invention, since the original instruction of the dummy disguised instruction is encrypted and the key used for encryption is disguised, it is possible to improve the difficulty of analyzing and falsifying the protection target program.

It is a block diagram which shows the structure of the self-rewriting processing apparatus which concerns on one Embodiment of this invention. It is a flowchart of the 1st process in the said self-rewriting processing apparatus. It is a flowchart of the 2nd process in the said self-rewriting processing apparatus. It is a figure for demonstrating a said 1st process and a said 2nd process. It is a figure for demonstrating a said 1st process and a said 2nd process. It is a figure for demonstrating a said 1st process and a said 2nd process. It is a figure for demonstrating a said 1st process and a said 2nd process. It is a figure for demonstrating a said 1st process and a said 2nd process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the constituent elements in the following embodiments can be appropriately replaced with existing constituent elements, and various variations including combinations with other existing constituent elements are possible. Accordingly, the description of the following embodiments does not limit the contents of the invention described in the claims.

[Configuration of Self-Rewriting Processing Device 1]
FIG. 1 is a block diagram showing a configuration of a self-rewriting processing device 1 according to an embodiment of the present invention. The self-rewriting processing device 1 includes a CPU (Central Processing Unit) 10 that performs various arithmetic processes, and a cache 20 that stores a protection target program.

  The self-rewrite processing device 1 executes the first process described later (see FIG. 2) and then executes the second process described later (see FIG. 3), thereby making it difficult to analyze and falsify the protection target program. To improve.

[First processing]
FIG. 2 is a flowchart of the first process described above.

  In step S1, the CPU 10 sets the bit size L to be encrypted (L is an integer satisfying L> 0) by the CPU 10, and moves the process to step S2. Specifically, the bit size L is obtained by multiplying the number of instructions to be encrypted and the number of bits per instruction. For example, when four instructions are encrypted in an environment where one instruction is 32 bits, the bit size L is 128 bits. Note that the number of instructions to be encrypted is determined, for example, by the user of the self-rewrite processing device 1.

  In step S2, the self-rewrite processing device 1 sets the number of iterations N (N is an integer satisfying N ≧ 0) by the CPU 10, and moves the process to step S3.

  In step S3, the self-rewrite processing device 1 initializes the variable P by substituting “0” for the variable P by the CPU 10, and moves the process to step S4.

  In step S4, the self-rewrite processing device 1 uses the CPU 10 to secure a data area for storing the encrypted instruction in the cache 20, and moves the process to step S5. Since the instruction is encrypted in step S23 of FIG. 3 described later, the encrypted instruction does not exist at the stage where step S4 is executed. For this reason, at the stage of executing step S4, null is stored in the data area secured in the cache 20 for storing the encrypted instruction.

  In step S5, the self-rewrite processing device 1 uses the CPU 10 to generate a key used when encrypting the instruction, secures a data area for storing the key in the cache 20, and uses the generated key as described above. Are stored in the secured data area, and the process proceeds to step S6. For the key generation, a pseudo random number for generating an encryption key is used. The pseudo random number for generating the encryption key may be generated by the CPU 10, or separately from the CPU 10, a random number generator that generates a random number and a sampling unit that samples the random number generated by the random number generator are provided. It may be generated by a random number generator and a sampling unit.

  In step S6, the self-rewriting processing device 1 selects an area to be protected from the protection target programs stored in the cache 20 by the CPU 10, and the process proceeds to step S7. It is assumed that the area to be protected is determined from the protection target program by the user of the self-rewrite processing device 1, for example. The protection target program stored in the cache 20 is described in a high-level language such as C language or Java (registered trademark).

  In step S7, the self-rewrite processing device 1 inserts the instruction decryption process into the protection target program that has undergone the process of step S6 by the CPU 10, and moves the process to step S8. The instruction decryption process is a process for decrypting an encrypted instruction. This instruction decoding process is inserted in front of the area selected in step S6 in the protection target program subjected to the process in step S6. Note that which instruction described in the protection target program is to be encrypted is determined in step S22 of FIG. 3 to be described later, so it is not known at the stage when step S7 is executed. For this reason, a temporary argument is assigned to the instruction decoding process at the stage of executing step S7.

  In step S8, the self-rewriting processing device 1 adds 1 to the variable P by the CPU 10, and proceeds to step S9.

  In step S <b> 9, the self-rewrite processing device 1 determines whether the variable P is equal to or less than the number of iterations N by the CPU 10. If the variable P is less than or equal to the number of iterations N, that is, if the number of times the processes in steps S7 and S8 are performed is less than or equal to the number of iterations N, the process returns to step S7. On the other hand, if the variable P is larger than the number of iterations N, that is, if the number of times the processes in steps S7 and S8 are performed is larger than the number of iterations N, the process proceeds to step S10.

  In step S10, the self-rewrite processing device 1 acquires an assembler description for the protection target program that has undergone the process of step S7 by the CPU 10, and ends the first process. Specifically, the protection target program that has undergone the process of step S7 is compiled and converted into an assembly program.

[Second processing]
FIG. 3 is a flowchart of the second process described above.

  In step S21, the self-rewrite processing device 1 initializes the variable Q by substituting “0” into the variable Q by the CPU 10, and moves the process to step S22.

  In step S22, the self-rewrite processing device 1 selects the first instruction set from the area corresponding to the area to be protected selected in step S6 among the protection target programs in the assembler description acquired in step S10 by the CPU 10. The process moves to step S23. The first instruction set is a set of instructions to be encrypted, and is composed of a number of instructions corresponding to the bit size L set in step S1. For example, in an environment where one instruction is 32 bits, when 128 bits is set as the bit size L, the first instruction set is composed of four instructions.

  In step S23, the self-rewrite processing device 1 encrypts the first instruction set by the CPU 10 using the key generated in step S5, and moves the process to step S24.

  In step S24, the self-rewrite processing device 1 stores the first instruction set encrypted in step S23 by the CPU 10 in the data area secured in step S4, and moves the process to step S25.

  In step S25, the CPU 10 replaces the first instruction set with a dummy first instruction set by the CPU 10, and moves the process to step S26. According to this, the first instruction set is camouflaged.

  In step S26, the self-rewrite processing device 1 causes the CPU 10 to specify the address of the first instruction set selected in step S22 and the address of the first instruction set stored in step S24 as arguments of the instruction decoding process inserted in step S7. And the process proceeds to step S27. According to this, when the instruction decryption process is executed after preparing the key, the first instruction set encrypted in step S23 is decrypted.

  In step S27, the self-rewrite processing device 1 uses the CPU 10 to insert an instruction restoration process into the protection target program that has undergone the process of step S26, and moves the process to step S28. The instruction restoration process is a process for replacing the dummy first instruction set with the original first instruction set. This instruction restoration process is performed between the instruction decoding process in which the argument is substituted in step S26 and the dummy first instruction set replaced in step S25 among the protection target programs subjected to the process of step S26. Inserted. According to this, after the instruction decoding process and the instruction restoration process are executed in this order, the first instruction set is executed.

  As described above, the first instruction set is encrypted in step S23. For this reason, if the instruction restoration process is executed without executing the instruction decryption process, the instruction restoration process is executed while the original first instruction set is encrypted. Therefore, the dummy first instruction set cannot be correctly replaced with the original first instruction set. However, in this embodiment, since the instruction restoration process is executed after the instruction decoding process is executed, the dummy first instruction set can be correctly replaced with the original first instruction set.

  In step S28, the self-rewrite processing device 1 uses the CPU 10 to insert the instruction disguise process into the protection target program that has undergone the process of step S27, and moves the process to step S29. The instruction disguise process is a process of replacing the original first instruction set with a dummy first instruction set. This instruction impersonation process is inserted behind the dummy first instruction set replaced in step S25 in the protection target program subjected to the process of step S27. According to this, after the first instruction set is executed, the instruction disguise process is executed. For this reason, after the first instruction set is executed, the first instruction set is camouflaged again.

  In step S29, the self-rewrite processing device 1 causes the CPU 10 to select the instruction set corresponding to the key used in step S23 as the second instruction set, and the process proceeds to step S30.

  In step S30, the self-rewrite processing device 1 uses the CPU 10 to replace the second instruction set with a dummy second instruction set, and the process proceeds to step S31. According to this, the second instruction set is camouflaged.

  In step S31, the self-rewrite processing device 1 inserts the key recovery process into the protection target program that has been processed in step S30 by the CPU 10, and moves the process to step S32. The key recovery process is a process of replacing the dummy second instruction set with the original second instruction set. This key recovery process is inserted in front of the instruction decryption process in which the argument is substituted in step S26 among the protection target programs subjected to the process of step S30. According to this, the instruction decryption process is executed after the key restoration process is executed. For this reason, when the instruction decryption process is executed, the forged key is returned to the original state.

  In step S32, the self-rewrite processing device 1 inserts the key disguise process into the protection target program that has performed the process of step S31 by the CPU 10, and moves the process to step S33. The key disguise process is a process for replacing the original second instruction set with a dummy second instruction set. This key impersonation process is inserted behind the instruction decryption process in which the argument is substituted in step S26 among the protection target programs subjected to the process of step S31. According to this, the key impersonation process is executed after the instruction decryption process is executed. For this reason, after the key is used in the instruction decryption process, the key is forged again.

  In step S33, the self-rewrite processing device 1 adds 1 to the variable Q by the CPU 10, and moves the process to step S34.

  In step S <b> 34, the self-rewrite processing device 1 determines whether the variable Q is equal to or less than the number of iterations N by the CPU 10. If the variable Q is less than or equal to the number of iterations N, that is, if the number of times the processes in steps S22 to S33 are performed is less than or equal to the number of iterations N, the process returns to step S22. On the other hand, if the variable Q is larger than the number of iterations N, that is, if the number of times the processes in steps S22 to S33 are performed is larger than the number of iterations N, the second process is terminated.

[Protected program after the first process and the second process]
First, the case where the number of iterations N is “1” and the above-described first process and the above-described second process are performed will be described below with reference to FIGS. 4 and 5.

  FIG. 4 is a diagram showing the protection target program 50 when the first process described above is performed with the iteration count N set to “1”.

  First, after each process of steps S1 to S4 is performed, a process of step S5 is performed, and a key used for encryption is generated and stored in a data area secured in the cache 20. For this reason, the key used for encryption is not described in the protection target program 50.

  Next, the process of step S6 is performed and the area to be protected is selected. In the selected area, an instruction set that is a set of instructions to be protected is described.

  Next, the process of step S7 is performed, and the instruction decoding process is inserted in front of the area selected in step S6, that is, in front of the instruction set to be protected. Note that when the instruction decoding process is inserted in step S7, the above-described process of step S26 is not performed, and therefore a temporary argument is assigned to the instruction decoding process.

  Next, after the processes of steps S8 and S9 are performed, the process of step S10 is performed, and the assembler description of the protection target program subjected to the process of step S7 is acquired. According to this, the instruction set to be protected is converted into the instruction set 51 to be protected described in the assembler, and the instruction decoding process is converted into the instruction decoding process 52 described in the assembler. It becomes.

  FIG. 5 is a diagram showing the protection target program 50A. The protection target program 50A is obtained by performing the above-described second process on the protection target program 50 shown in FIG.

  First, after the process of step S21 is performed, the process of step S22 is performed and the first instruction set is selected. Here, it is assumed that the instruction set 51 to be protected shown in FIG. 4 is selected as the first instruction set.

  Next, the process of step S23 is performed, and the instruction set 51 to be protected as the first instruction set is encrypted. Since the encrypted first instruction set is stored in the data area secured in step S4 in step S24, it is not described in the protection target program 50A.

  Next, the process of step S25 is performed, and the instruction set 51 to be protected as the first instruction set is replaced with a dummy first instruction set 51A and is camouflaged.

  Next, the process of step S26 is performed, and the dummy argument of the instruction decoding process 52 shown in FIG. 4 is replaced with each address described above. Here, the instruction decoding process 52A is obtained by performing the process of step S26 on the instruction decoding process 52 shown in FIG.

  Next, the process of step S27 is performed, and the instruction restoration process 53 is inserted between the instruction decoding process 52A and the dummy first instruction set 51A.

  Next, the process of step S28 is performed, and the instruction disguise process 54 is inserted behind the dummy first instruction set 51A.

  Next, after the process of step S29 is performed, the process of step S30 is performed, and the key used when encrypting the instruction set 51 to be protected in step S23 is replaced with a dummy key and impersonated. The

  Next, the process of step S31 is performed, and the key recovery process 55 is inserted in front of the instruction decryption process 52A.

  Next, the process of step S32 is performed, and the key impersonation process 56 is inserted behind the instruction decryption process 52A.

  Next, the case where the number of iterations N is “2” and the above-described first process and the above-described second process are performed will be described below with reference to FIGS. 6 to 8.

  FIG. 6 is a diagram showing the protection target program 60 when the above-described first processing is performed with the iteration count N being “2”.

  The protection target program 60 differs from the protection target program 50 shown in FIG. 4 in the number of instruction decoding processes to be inserted. Specifically, instruction decoding processes 621 and 622 are inserted into the protection target program 60 in front of the instruction set 61 to be protected.

  FIG. 7 is a diagram showing the protection target program 60A. The protection target program 60A is obtained by performing each of the processes of steps S22 to S33 once after performing the process of step S21 on the protection target program 60 shown in FIG.

  In the protection target program 60A, as in the protection target program 50A, in step S22, the instruction set 61 to be protected is selected as the first instruction set, and the processes in steps S23 to S33 are performed on the instruction set 61 to be protected. For this reason, the protection target program 60A includes a key restoration process 55, an instruction decryption process 52A, a key impersonation process 56, an instruction restoration process 53, a dummy first instruction set 51A, and an instruction of the protection target program 50A shown in FIG. As corresponding to each of the impersonation processes 54, a key restoration process 65, an instruction decryption process 621A, a key impersonation process 66, an instruction restoration process 63, a dummy first instruction set 61A, and an instruction impersonation process 64 are described. It becomes. In the protection target program 60A, the instruction decryption process 622 shown in FIG.

  FIG. 8 is a diagram showing the protection target program 60B. The protection target program 60B is obtained by performing each process of steps S22 to S33 once for the protection target program 60A shown in FIG.

  First, after the process of step S21 is performed, the process of step S22 is performed and the first instruction set is selected. Here, it is assumed that the key recovery process 65 shown in FIG. 7 is selected as the first instruction set.

  Next, the process of step S23 is performed, and the key restoration process 65 as the first instruction set is encrypted. Since the encrypted first instruction set is stored in the data area secured in step S4 in step S24, it is not described in the protection target program 60B.

  Next, the process of step S25 is performed, and the key restoration process 65 as the first instruction set is replaced with a dummy first instruction set 65A and is camouflaged.

  Next, the process of step S26 is performed, and the dummy argument of the instruction decoding process 622 shown in FIG. 7 is replaced with each address described above. Here, the instruction decoding process 622A is obtained by performing the process of step S26 on the instruction decoding process 622 shown in FIG.

  Next, the process of step S27 is performed, and the instruction restoration process 653 is inserted between the instruction decoding process 622A and the dummy first instruction set 65A.

  Next, the process of step S28 is performed, and an instruction forgery process 654 is inserted behind the dummy first instruction set 65A.

  Next, after the process of step S29 is performed, the process of step S30 is performed, and the key used when encrypting the key recovery process 65 in step S23 is replaced with a dummy key and impersonated. .

  Next, the process of step S31 is performed, and the key recovery process 655 is inserted in front of the instruction decryption process 622A.

  Next, the process of step S32 is performed, and the key impersonation process 656 is inserted behind the instruction decryption process 622A.

  According to the self-rewriting processing device 1 described above, the following effects can be obtained.

  The self-rewriting processing device 1 performs the process of step S25, replaces the instruction described in the protection target program with a dummy instruction, and performs the process of step S23 to encrypt the original instruction. According to this, the original instruction of the instruction disguised as a dummy is in an encrypted state.

  Further, the self-rewriting processing device 1 performs the process of step S30, and pretend to be a dummy key the key used when encrypting the instruction in step S23.

  According to the above, since the self-rewrite processing device 1 encrypts the original instruction of the dummy disguised instruction and disguises the key used for encryption, it improves the difficulty of analyzing and falsifying the protection target program. be able to.

  Further, the self-rewriting processing device 1 repeats the processes of steps S7 and S8 and the processes of steps S22 to S33 for the number of repetitions N set in step S2. For this reason, since it is possible to perform the impersonation of the instruction described in the protection target program, the encryption of this instruction, and the impersonation of the key used for the encryption multiple times, the analysis and alteration of the protection target program can be performed. The difficulty can be further improved.

  The embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments, and includes designs and the like that do not depart from the gist of the present invention.

  For example, in the above-described embodiment, the key is generated in step S5. However, the present invention is not limited to this. For example, the key may be generated in advance by a device different from the self-rewriting processing device 1.

  In the above-described embodiment, the instruction impersonation process is inserted in step S28. For this reason, when the instruction disguise process is executed, the original instruction is replaced with a dummy instruction. Here, the dummy instruction replaced by the execution of the instruction impersonation process may be the same as or different from the dummy instruction replaced in step S25. Also, with respect to the key used when encrypting the instruction, the dummy key replaced by executing the key impersonation process inserted in step S32 may be the same as the dummy key replaced in step S30. , May be different.

  In the above-described embodiment, after the instruction restoration process is inserted in step S27, the instruction impersonation process is inserted in step S28. However, the present invention is not limited to this, and the instruction restoration process is inserted after the instruction impersonation process is inserted. It is good to do. Also, with regard to the key restoration process and the key impersonation process, the key restoration process may be inserted after the key impersonation process is inserted.

  In the above-described embodiment, the number of iterations N is set in step S2. Here, as the number of iterations N is increased, it is possible to improve the difficulty of analyzing and falsifying the protection target program. On the other hand, when executing the protection target program processed by the self-rewrite processing device 1 Performance is degraded. For this reason, the number of iterations N is determined in consideration of the degree of difficulty in analyzing and falsifying the protection target program and the performance when the protection target program processed by the self-rewrite processing device 1 is executed. Is preferred.

DESCRIPTION OF SYMBOLS 1 ... Self-rewriting processing apparatus 10 ... CPU
20 ... cache 50, 50A, 60, 60A, 60B ... protection target program

Claims (5)

Storage means for storing the protection target program;
Selecting means for selecting at least one instruction described in the protection target program;
An instruction encryption means for encrypting the instruction selected by the selection means using a key;
A key disguise means for replacing the key used by the instruction encryption means with a dummy key;
A key restoration process insertion means for inserting a key restoration process for replacing the dummy key replaced by the key impersonation means with the original key into the protection target program;
Instruction decryption processing insertion means for inserting into the protection target program instruction decryption processing for decrypting the instruction encrypted by the instruction encryption means using the original key replaced by execution of the key recovery processing;
A key impersonation process insertion means for inserting a key impersonation process in which the original key replaced by the execution of the key restoration process is replaced with a dummy key into the protection target program;
Instruction disguise means for replacing the instruction selected by the selection means with a dummy instruction;
Instruction restoration processing insertion means for inserting, into the protection target program, instruction restoration processing for replacing the dummy instruction replaced by the instruction disguise means with the original instruction decoded by execution of the instruction decoding processing;
A self-rewrite processing device comprising: an instruction disguise process insertion means for inserting an instruction disguise process for replacing an original instruction replaced by execution of the instruction restore process with a dummy instruction into the protection target program; . The instruction decoding process insertion means inserts the instruction decoding process ahead of a dummy instruction replaced by the instruction disguise means in the protection target program,
The instruction restoration process insertion means inserts the instruction restoration process between the instruction decoding process and the dummy instruction replaced by the instruction impersonation means in the protection target program,
The instruction impersonation process insertion means inserts the instruction impersonation process behind the dummy instruction replaced by the instruction impersonation means in the protection target program,
The key recovery process insertion means inserts the key recovery process ahead of the instruction decryption process in the protection target program,
The self-rewriting processing device according to claim 1, wherein the key impersonation processing insertion unit inserts the key impersonation processing behind the instruction decryption processing in the protection target program.   Selection by the selection means, encryption by the instruction encryption means, replacement by the key impersonation means, insertion by the key restoration processing insertion means, insertion by the instruction decryption processing insertion means, and insertion of the key impersonation processing The insertion by the means, the replacement by the instruction impersonation means, the insertion by the instruction restoration processing insertion means, and the insertion by the instruction impersonation processing insertion means are repeated a predetermined number of times. 2. The self-rewriting processing device according to 2. Self-rewriting comprising selection means, instruction encryption means, key impersonation means, key restoration processing insertion means, instruction decryption processing insertion means, key impersonation processing insertion means, instruction impersonation means, instruction restoration processing insertion means, and instruction impersonation processing insertion means A self-rewriting processing method in a processing device,
A first step in which the selection means selects at least one instruction described in the protection target program;
A second step in which the instruction encryption means encrypts the instruction selected in the first step using a key;
A third step in which the key disguise means replaces the key used in the second step with a dummy key;
A fourth step in which the key restoration processing inserting means inserts a key restoration processing in which the dummy key replaced in the third step is replaced with the original key into the protection target program;
The instruction decryption process inserting means inserts an instruction decryption process for decrypting the instruction encrypted in the second step using the original key replaced by the execution of the key restoration process into the protection target program. 5 steps,
A sixth step in which the key impersonation process insertion means inserts into the protection target program a key impersonation process that replaces the original key replaced by the execution of the key restoration process with a dummy key;
A seventh step in which the instruction disguise means replaces the instruction selected in the first step with a dummy instruction;
The instruction restoring process inserting means inserts into the protected program an instruction restoring process that replaces the dummy instruction replaced in the seventh step with the original instruction decoded by executing the instruction decoding process. Steps,
The instruction spoofing process inserting means includes a ninth step of inserting into the protection target program an instruction spoofing process that replaces the original instruction replaced by the execution of the instruction restoration process with a dummy instruction. Self-rewriting processing method. A first step of selecting at least one instruction described in the protection target program;
A second step of encrypting the instruction selected in the first step using a key;
A third step of replacing the key used in the second step with a dummy key;
A fourth step of inserting, into the protection target program, a key restoration process for replacing the dummy key replaced in the third step with the original key;
A fifth step of inserting, into the protection target program, an instruction decryption process for decrypting the instruction encrypted in the second step using the original key replaced by the execution of the key recovery process;
A sixth step of inserting, into the protection target program, a key impersonation process for replacing the original key replaced by the execution of the key restoration process with a dummy key;
A seventh step of replacing the instruction selected in the first step with a dummy instruction;
An eighth step of inserting into the protection target program an instruction restoration process that replaces the dummy instruction replaced in the seventh step with the original instruction decoded by executing the instruction decoding process;
A program for causing a computer to execute a ninth step of inserting, into the protection target program, an instruction disguise process for replacing an original instruction replaced by execution of the instruction restoration process with a dummy instruction.

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