Patent Publication Number: US-9891862-B2

Title: Forensic data acquisition apparatus and method for guaranteeing integrity of flash memory in smart device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2015-0103239, filed Jul. 21, 2015, which is hereby incorporated by reference in its entirety into this application. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention generally relates to technology for acquiring forensic data stored in flash memory in a smart device and, more particularly, to technology for acquiring forensic data in the state in which only a boot loader and a Universal Serial Bus (USB) module are activated in order to guarantee the integrity of data. 
     2. Description of the Related Art 
     Recently, with the advent of various smart devices such as smart phones, smart TVs, and wearable devices, various technologies that are used for business purposes as well as personal purposes have appeared. As a result, the incidence of mobile crime, involving for example various malicious code and smishing, which are intended for smart devices, has rapidly increased, and thus the importance of mobile forensics has gradually increased. Therefore, research into methods for acquiring the entire contents of flash memory in order to restore deleted files and analyze details is required. 
     Conventional methods for acquiring data from smart devices have acquired data using a rooting method based on the vulnerability of a kernel. However, such methods do not support data acquisition for the latest Operating System (OS) until a new vulnerability is discovered because vulnerability to rooting is patched with the upgrade of an OS version. Further, with the application of security technology such as secure boot and Samsung&#39;s Knox, it has become more and more difficult to acquire data. Such a method is configured such that, after rooting, a data acquisition procedure is performed. During the rooting procedure, a system and data falsification procedure occurs, and thus a problem arises in that the integrity of the acquired flash memory data is not maintained. 
     As another data acquisition method, there is a method for acquiring data by replacing a custom recovery image. This method is a method of accessing a user data area by replacing only a recovery area, and relates to research into the guarantee of the integrity of the user data area. However, this method is problematic in that, since a custom recovery image is flashed, it is impossible to guarantee the integrity of dump images of the entire contents of flash memory. 
     Hardware-based acquisition methods may include a method utilizing a Joint Test Action Group (JTAG) port on a Printed Circuit Board (PCB). However, recently, for reasons of security, manufactures have a tendency to remove or deactivate a JTAG port on a PCB. As another hardware-based method for acquiring data, there is a method of removing flash memory from a given device (chip-off) and then acquiring data, but it is limited in that data may be acquired only when a power failure occurs or a fault occurs due to a problem such as damage to the smart device that contains evidence. 
     Korean Patent No. 1046025 discloses technology for extracting data from an embedded system. In particular, there is disclosed technology for extracting data from flash memory in the form of binary code using a JTAG interface on a PCB in an embedded system. However, Korean Patent No. 1046025 cannot acquire data in the state in which a JTAG port is connected to a JTAG emulator. In other words, when the JTAG port is deactivated, the disclosed technology cannot be used. In light of the recent tendency to deactivate the JTAG port on PCBs in smart devices in order to realize information protection, Korean Patent No. 1046025 has a fatal disadvantage in that the JTAG port must be essentially used. 
     Therefore, in response to the increased popularity of smart devices and the necessity to collect evidentiary data for evidence in solving crimes, technology that acquires forensic data without damaging a smart device containing evidentiary data is required. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to acquire forensic data without damaging a smart device that contains evidence. 
     Another object of the present invention is to acquire forensic data while guaranteeing the integrity of flash memory in a smart device that contains evidence. 
     In accordance with an aspect of the present invention to accomplish the above objects, there is provided a forensic data acquisition apparatus, including a command analysis unit for activating a boot loader and a Universal Serial Bus (USB) module of a smart device and analyzing a format of a flash memory read command using the boot loader, a partition information analysis unit for analyzing partition information of flash memory in compliance with the flash memory read command; and a data acquisition unit for generating a dump image by dumping data stored in the flash memory based on the flash memory read command and the partition information, and for acquiring forensic data based on the dump image. 
     The command analysis unit may cause the smart device to enter a firmware update mode and then enable only the boot loader and the USB module to be activated. 
     The command analysis unit may analyze the smart device, determine resistance between pins 4 and 5 of a USB cable for connecting the smart device that is intended to enter the firmware update mode to the forensic data acquisition apparatus, and control the USB cable based on the resistance, thus causing the smart device to enter the firmware update mode. 
     The command analysis unit may analyze the flash memory read command based on results of analysis of a firmware update protocol for firmware in a Secondary Boot Loader (SBL) and in an Android boot loader (Aboot) provided in the boot loader. 
     The flash memory read command may include a read command signature field, a flash memory start address field, a dump size field, and a read command end field. 
     The command analysis unit may be configured to, when the smart device is powered on, terminate the smart device and enter the firmware update mode. 
     The partition information analysis unit may include a partition type analysis unit for analyzing types of partitions based on a partition signature of the flash memory; and an information analysis unit for parsing partition table values corresponding to the partitions and analyzing one or more of a size of the flash memory, names of the partitions, start addresses of the partitions, and end addresses of the partitions. 
     The data acquisition unit may include a mode selection unit for selecting any one of a whole flash memory dump mode and a partition dump mode for the partitions in the flash memory; a whole dump performance unit for, when the whole flash memory dump mode is selected, performing a dump at a selected dump image selection location in units of sectors; and a partition dump performance unit for, when the partition dump mode is selected, performing a dump at a dump image generation location corresponding to each selected partition in units of sectors of the partition. 
     The forensic data acquisition apparatus may further include an integrity verification unit for generating a hash value using the data and a hash function and verifying integrity of the data using the hash value. 
     The forensic data acquisition apparatus may further include an output unit for outputting a procedure for generating the hash value and the dump image. 
     In accordance with another aspect of the present invention to accomplish the above objects, there is provided a forensic data acquisition method, including activating a boot loader and a Universal Serial Bus (USB) module of a smart device and analyzing a format of a flash memory read command based on results of analysis of the boot loader, analyzing partition information of flash memory in compliance with the flash memory read command; and generating a dump image by dumping data stored in the flash memory based on the flash memory read command and the partition information, and acquiring forensic data based on the dump image. 
     Analyzing the format of the flash memory read command format may be configured to cause the smart device to enter a firmware update mode and then enable only the boot loader and the USB module to be activated. 
     Analyzing the format of the flash memory read command may be configured to analyze the smart device, determine resistance between pins 4 and 5 of a USB cable for connecting the smart device that is intended to enter the firmware update mode to the forensic data acquisition apparatus, and control the USB cable based on the resistance, thus causing the smart device to enter the firmware update mode. 
     Analyzing the format of the flash memory read command may be configured to analyze the flash memory read command based on results of analysis of a firmware update protocol for firmware in a Secondary Boot Loader (SBL) and an Android boot loader (Aboot) provided in the boot loader. 
     The flash memory read command may include a read command signature field, a flash memory start address field, a dump size field, and a read command end field. 
     Analyzing the format of the flash memory read command may be configured to, when the smart device is powered on, terminate the smart device and enter the firmware update mode. 
     Analyzing the partition information may include analyzing types of partitions based on a partition signature of the flash memory; and parsing partition table values corresponding to the partitions and analyzing one or more of a size of the flash memory, names of the partitions, start addresses of the partitions, and end addresses of the partitions. 
     Acquiring the forensic data may include selecting any one of a whole flash memory dump mode and a partition dump mode for the partitions in the flash memory; when the whole flash memory dump mode is selected, performing a dump at a selected dump image selection location in units of sectors; and when the partition dump mode is selected, performing a dump at a dump image generation location corresponding to each selected partition in units of sectors of the partition. 
     The forensic data acquisition method may further include generating a hash value using the data and a hash function and verifying integrity of the data using the hash value. 
     The forensic data acquisition method may further include outputting a procedure for generating the hash value and the dump image. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram showing a forensic data acquisition apparatus according to an embodiment of the present invention; 
         FIG. 2  is a block diagram showing the partition information analysis unit shown in  FIG. 1 ; 
         FIG. 3  is a block diagram showing the data acquisition unit shown in  FIG. 1 ; 
         FIG. 4  is a diagram showing the state in which a smart device enters a firmware update mode in the forensic data acquisition apparatus according to an embodiment of the present invention; 
         FIG. 5  is a diagram showing a screen output after the smart device enters a firmware update mode in the forensic data acquisition apparatus according to an embodiment of the present invention; 
         FIG. 6  is a diagram showing the procedure in which the smart device is booted in the forensic data acquisition apparatus according to an embodiment of the present invention; 
         FIG. 7  is a diagram showing a screen on which the forensic data acquisition apparatus acquires and outputs partition information according to an embodiment of the present invention; 
         FIGS. 8 and 9  are diagrams showing a command format for reading flash memory in the forensic data acquisition apparatus according to an embodiment of the present invention; 
         FIG. 10  is an operation flowchart showing a forensic data acquisition method according to an embodiment of the present invention; 
         FIG. 11  is an operation flowchart showing the state in which a smart device enters a firmware update mode in the forensic data acquisition method according to an embodiment of the present invention; 
         FIG. 12  is an operation flowchart showing the procedure for analyzing partition information in the forensic data acquisition method according to an embodiment of the present invention; and 
         FIG. 13  is an operation flowchart showing the procedure for dumping flash memory in the forensic data acquisition method according to an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be described in detail below with reference to the accompanying drawings. Repeated descriptions and descriptions of known functions and configurations which have been deemed to make the gist of the present invention unnecessarily obscure will be omitted below. The embodiments of the present invention are intended to fully describe the present invention to a person having ordinary knowledge in the art to which the present invention pertains. Accordingly, the shapes, sizes, etc. of components in the drawings may be exaggerated to make the description clearer. 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. 
       FIG. 1  is a block diagram showing a forensic data acquisition apparatus according to an embodiment of the present invention. 
     Referring to  FIG. 1 , the forensic data acquisition apparatus according to the embodiment of the present invention includes a command analysis unit  110 , a partition information analysis unit  120 , and a data acquisition unit  130 . 
     The command analysis unit  110  enters a firmware update mode for firmware in the boot loader of a smart device to activate a boot loader and a USB module, and analyze the format of the flash memory read command corresponding to the firmware update mode. 
     Since the firmware update mode corresponds to the state in which only the boot loader and the USB module are activated, the integrity of data may be guaranteed even if a physical dump is performed multiple times. Existing data acquisition technologies use kernel vulnerability-based rooting, a method of replacing custom recovery, or a method of acquiring hardware data via JTAG and chip-off techniques. However, such conventional technology is problematic in that the system and user data areas in flash memory may be falsified, the recovery area may be compromised, or the integrity of evidentiary data may be damaged due to the disassembly and reassembly of hardware. However, in the firmware update mode, since only the boot loader and the USB module are activated, the integrity of data may be guaranteed. 
     The smart device denotes an embedded system-equipped device, such as a smart phone, a smart TV, a wearable smart watch, or an Internet of Things (IoT) smart device. 
     Here, methods of entering the firmware update mode for respective system manufacturers differ from each other. However, such a firmware update mode is necessarily present in all smart devices in order to release new OS versions and patch software. 
     Each smart device may enter the firmware update mode via the manipulation of a button key in the state in which the system is powered off. 
     To enter the firmware update mode, the command analysis unit  110  may enter the firmware update mode using resistance between pins 4 and 5 of a USB cable for connecting the smart device to the forensic data acquisition apparatus. 
     In the case of the USB cable, the access mode may differ depending on the resistance between pins 4 and 5. That is, the smart device may enter the firmware update mode depending on the resistance between pins 4 and 5. For example, when the resistance between pins 4 and 5 is 300 KΩ, a specific smart phone may enter the firmware update mode. When the resistance between pins 4 and 5 is 910 KΩ, another smart phone may enter the firmware update mode. That is, the command analysis unit  110  may determine the resistance between pins 4 and 5 of the USB cable for connecting the smart device that desires to enter the firmware update mode to the forensic data acquisition apparatus, and may control the USB cable based on the determined resistance, thus entering the firmware update mode. 
     The scheme for entering the firmware update mode may differ for each smart device. Referring to  FIG. 4 , the scheme for entering the firmware update mode may differ for each model. For example, to enter the firmware update mode in High-Tech Computer (HTC)&#39;s model, shown in  FIG. 4 , a method of simultaneously pressing a volume-down key and a power key may be used. However, to enter the firmware update mode in Samsung&#39;s Galaxy, a method of simultaneously pressing a volume-down key, a home key, and a power key or of utilizing a USB cable having 300 KΩ may be used. 
     Once the firmware update mode has been entered, the screen output of the smart device is as illustrated in  FIG. 5 . Referring to  FIG. 5 , it can be seen that the screen output of the smart device at ordinary times is different from the screen output of the smart device in the firmware update mode. 
     Here, the command analysis unit  110  may analyze a flash memory read command. In the case of the flash memory read command, the command analysis unit  110  may analyze a firmware update protocol, and then analyze a flash memory access command format and a flash memory read command format. 
     Here, the firmware update protocol may be independently implemented by each existing manufacturer, and does not follow an open standard format. Therefore, a new model that does not use the existing firmware update protocol requires a task of analyzing the firmware update protocol, in which both a flash memory access command format and a flash memory read command format are stored. The firmware update protocol is implemented in a Secondary Boot Loader (SBL) or an Android boot loader (Aboot) provided in a boot loader, and thus the SBL or Aboot is analyzed, thus enabling the new flash memory access command and the new flash memory read command to be analyzed. A detailed description thereof will be made later with reference to  FIG. 6 . 
     In this case, the command analysis unit  110  sends a model information identification command to the system corresponding to the smart device, and determines whether the system is a model in which a dump function is supported. If the system is a new model in which a dump function is not supported, the command analysis unit  110  may analyze a firmware update protocol in the boot loader and then analyze a flash memory access command format and a flash memory read command format. 
     The partition information analysis unit  120  analyzes the partition information of the flash memory in compliance with the flash memory read command. 
     Recent smart devices mainly use a package structure in which NAND flash memory, called an Embedded Multi Media Card (Emmc), and a controller are integrated, and efficiently manage stored data using a file system, such as Yet Another Flash File System (YAFFS) or External File system (EXT) 3/4. Further, partitions such as BOOT, RECOVERY, SYSTEM, and USERDATA are mounted and used in smart devices using a partition function. To acquire data from such flash memory, information about the partitions of the flash memory is required. 
     Each smart device may access the partition signature of the flash memory using a flash memory read command, and may analyze the types of partitions using the partition signature. 
     Here, the types of partitions may include a Master Boot Record (MBR), a GUID Partition Table (GPT), etc. 
     The partition table values corresponding to the partitions are parsed, so that the size of the flash memory, the names of the partitions, the address at which each partition starts, and the address at which each partition ends may be analyzed. 
     The results of analysis may be output via an output unit, and are illustrated in  FIG. 7 . Referring to  FIG. 7 , the total number of partitions, the names of the partitions, and the start addresses and end addresses of the partitions are illustrated. 
     The data acquisition unit  130  dumps the data stored in the flash memory based on the flash memory read command and the partition information, generates a dump image, and acquires forensic data based on the dump image. 
     Here, the data acquisition unit  130  may select any one of a whole flash memory dump mode, in which the entire contents of flash memory are dumped, and a partition dump mode, in which the contents of partitions in the flash memory are dumped. When the whole flash memory dump mode is selected, a dump may be performed at the selected dump image generation location in units of sectors of the flash memory. Meanwhile, when the partition dump mode is selected, a dump is performed at the dump image generation location corresponding to each partition in units of sectors in the partition, and then a dump image may be generated. In the present invention, in the firmware update mode in which only the boot loader and the USB module are activated, an image may be physically dumped. As a result, even if data is repeatedly acquired multiple times, the integrity of the data may be maintained without falsifying original evidentiary data. 
     Here, when the whole flash memory dump mode is selected, the data acquisition unit  130  may calculate the size and dump time of the whole flash memory and select the location at which a dump image is to be generated. The dumping size implemented by one flash memory read command may be set to the form of a multiple of 512 bytes, which is the sector size of the flash memory. When the dump is completed up to the last sector, a hash value for the acquired dump image may be generated. 
     Here, when the partition dump mode is selected, the data acquisition unit  130  may calculate the size and dump time of each partition and select the location at which a partition dump image is to be generated. A data acquisition procedure is performed for each selected partition. When the dump is completed up to the last sector of each partition, hash values for the acquired partition dump images may be generated. 
     Here, although not shown in  FIG. 1 , the forensic data acquisition apparatus may further include an integrity verification unit (not shown) for generating a hash value using data and a hash function and verifying the integrity of the data using the hash value, in order to verify the integrity of the acquired data. Since a hash function is generally used to verify the integrity of data, the present invention may use a hash function to verify the integrity of the acquired data (forensic data). 
     The forensic data acquisition apparatus according to the embodiment of the present invention may further include an output unit (or display unit) (not shown) for visualizing and outputting the hash value, generated by the integrity verification unit (not shown), and the data acquisition procedure. 
       FIG. 2  is a block diagram showing the partition information analysis unit shown in  FIG. 1 . 
     Referring to  FIG. 2 , the partition information analysis unit  120  includes a partition type analysis unit  210  and an information analysis unit  220 . 
     In recent smart devices, a package structure in which NAND flash memory, called an Embedded Multi Media Card (Emmc), and a controller are integrated is mainly used. The stored data is efficiently managed using a file system such as Yet Another Flash File System (YAFFS) or EXT 3/4. Further, partitions, such as BOOT, RECOVERY, SYSTEM, and USERDATA, are mounted and used using a partition function. To acquire data from such flash memory, information about the partitions of the flash memory is required. 
     The partition type analysis unit  210  analyzes the types of partitions based on the partition signature of the flash memory. 
     The partition signature is data indicating the types of partitions. The types of partitions may include an MBR, a GPT, etc. To access the partition signature, the partition signature may be accessed using the flash memory read command analyzed by the command analysis unit  110 . 
     The information analysis unit  220  parses partition table values corresponding to partitions, and analyzes the size of flash memory, the names of partitions, and the start addresses and end addresses of the partitions. 
     The results of analysis are transmitted to the data acquisition unit  130 , and the data acquisition unit  130  dumps data stored in the flash memory using the partition information. 
     In this case, the results of analysis may be output via the output unit, and are illustrated in  FIG. 7 . Referring to  FIG. 7 , the total number of partitions, the names of partitions, and the start and end addresses of the partitions are illustrated. 
       FIG. 3  is a block diagram showing the data acquisition unit shown in  FIG. 1 . 
     A mode selection unit  310  selects any one of a whole flash memory dump mode and a partition dump mode for partitions in the flash memory. 
     The whole flash memory dump mode denotes a mode in which all of the data stored in the flash memory is dumped. 
     The partition dump mode denotes a mode in which the data in partitions in the flash memory is dumped. 
     A whole dump performance unit  320  is configured to, when the whole flash memory dump mode is selected, perform a dump at a selected dump image generation location in units of sectors of the flash memory. 
     Here, the whole dump performance unit  320  is configured to, when the whole flash memory dump mode is selected, calculate the size and dump time of the whole flash memory, and select the location at which a dump image is to be generated. The dumping size implemented by one flash memory read command may be set to the form of a multiple of 512 bytes, which is the sector size of the flash memory. When the dump is completed up to the last sector, a hash value for the acquired dump image may be generated. 
     The partition dump performance unit  330  is configured to, when the partition dump mode is selected, perform a dump at the dump image generation location corresponding to each partition in units of sectors of the partition. 
     Here, the partition dump performance unit  330  is configured to, when the partition dump mode is selected, calculate the size and dump time of each partition and select the location where the partition dump image is to be generated. During the data acquisition procedure for each selected partition, when the dump has been completed up to the last sector of the selected partition, hash values for the acquired partition dump images may be generated. 
       FIG. 6  is a diagram showing the procedure in which a smart device is booted in the forensic data acquisition apparatus according to an embodiment of the present invention. 
     The procedure in which the smart device is booted is performed such that, when the system is powered on, the Read Only Memory (ROM) of the smart device is executed from address 0, and required initialization such as Central Processing Unit (CPU) configuration is performed. Thereafter, while a boot loader is loaded into the memory, tasks of initializing and configuring hardware, such as NAND or USB memory, are performed. This boot loader execution procedure is subjected to several stages, such as an Initial Boot Loader (IBL), Primary Boot Loader (PBL), and Secondary Boot Loader (SBL). A typical firmware update protocol is implemented in the SBL or Aboot. Therefore, when the SBL or Aboot is analyzed, a flash memory access command and a flash memory read command may be analyzed. 
     Referring to  FIG. 6 , after ROM has been operated, booting is performed in the sequence of SBL 1 , SBL 2 , SBL 3 , Aboot, and BOOT/RECOVERY. In  FIG. 6 , since the firmware update protocol is implemented in SBL 3 , both a flash memory access command and a flash memory read command may be analyzed if the SBL 3  boot loader is analyzed. 
       FIGS. 8 and 9  are diagrams showing the command format used to read flash memory in the forensic data acquisition apparatus according to an embodiment of the present invention. 
     First, the flash memory read command uses each manufacturer&#39;s own packet format in the firmware update protocol of the manufacturer. Therefore, in the case of a new model that does not use an existing firmware update protocol, the procedure for reversely analyzing the boot loader, analyzing the firmware update protocol, and then identifying the flash memory read command is required. 
     The whole flash memory read command is illustrated in  FIG. 8 . The format of the whole flash memory read command may be configured in such a way that a read command signature field, a flash memory start address field, a dump size field, and a read command end field are sequentially arranged. In the lower portion of  FIG. 8 , the screen on which acquired data is visually output is illustrated. 
     In  FIG. 9 , the partition read command is illustrated. The format of the partition read command may be configured in such a way that a read command signature field, a partition name or ID field, a partition start address field, a dump size field, and a read command end field are sequentially arranged. In the lower portion of  FIG. 9 , the screen on which the acquired data is visually output is illustrated. 
       FIG. 10  is an operation flowchart showing a forensic data acquisition method according to an embodiment of the present invention. 
     Referring to  FIG. 10 , the smart device enters a firmware update mode for firmware in the boot loader thereof at step S 1010 . 
     Here, when the smart device enters the firmware update mode, only the boot loader and the USB module of the smart device are activated, and remaining programs may be deactivated. 
     Since the firmware update mode corresponds to the state in which only the boot loader and the USB module are activated, the integrity of data may be guaranteed even if a physical dump is performed multiple times. Conventional data acquisition technologies use kernel vulnerability-based rooting, a method of replacing custom recovery, and a method of acquiring hardware data via JTAG and chip-off techniques. However, such conventional technology is problematic in that the system and user data areas in the flash memory may be falsified, the recovery area may be compromised, or the integrity of evidentiary data may be damaged due to the disassembly and reassembly of hardware. However, since, in the firmware update mode, only the boot loader and the USB module are activated and the remaining programs are deactivated, the integrity of data may be guaranteed. 
     The smart device denotes an embedded system-equipped device, such as a smart phone, a smart TV, a wearable smart watch, or an Internet of Things (IoT) smart device. 
     Here, methods of entering the firmware update mode for respective system manufacturers differ from each other. However, such a firmware update mode is necessarily present in all smart devices in order to release new OS versions and patch software. 
     Each smart device may enter the firmware update mode via the manipulation of a button key in the state in which the system is powered off. 
     To enter the firmware update mode, the command analysis unit  110  may enter the firmware update mode using resistance between pins 4 and 5 of a USB cable for connecting the smart device to the forensic data acquisition apparatus. 
     In the case of the USB cable, the access mode may differ depending on the resistance between pins 4 and 5. That is, the smart device may enter the firmware update mode depending on the resistance between pins 4 and 5. For example, when the resistance between pins 4 and 5 is 300 KΩ, a specific smart phone may enter the firmware update mode. When the resistance between pins 4 and 5 is 910 KΩ, another smart phone may enter the firmware update mode. That is, the command analysis unit  110  may determine the resistance between pins 4 and 5 of the USB cable for connecting the smart device that desires to enter the firmware update mode to the forensic data acquisition apparatus, and may control the USB cable based on the determined resistance, thus entering the firmware update mode. 
     The scheme for entering the firmware update mode may differ for each smart device. Referring to  FIG. 4 , the scheme for entering the firmware update mode may differ for each model. For example, to enter the firmware update mode in High-Tech Computer (HTC)&#39;s model, shown in  FIG. 4 , a method of simultaneously pressing a volume-down key and a power key may be used. However, to enter the firmware update mode in Samsung&#39;s Galaxy, a method of simultaneously pressing a volume-down key, a home key, and a power key or of utilizing a USB cable having 300 KΩ may be used. 
     Once the firmware update mode has been entered, the screen output of the smart device is as illustrated in  FIG. 5 . Referring to  FIG. 5 , it can be seen that the screen output of the smart device at ordinary times is different from the screen output of the smart device in the firmware update mode. 
     Further, a read command for flash memory is analyzed at step S 1020 . 
     Here, the command analysis unit  110  may analyze a flash memory read command. In the case of the flash memory read command, the command analysis unit  110  may analyze a firmware update protocol, and then analyze a flash memory access command format and a flash memory read command format. 
     The firmware update protocol may be independently implemented by each existing manufacturer, and does not follow an open standard format. Therefore, a new model that does not use the existing firmware update protocol requires a task of analyzing the firmware update protocol, in which both a flash memory access command format and a flash memory read command format are stored. The firmware update protocol is implemented in a Secondary Boot Loader (SBL) or an Android boot loader (Aboot) provided in a boot loader, and thus the SBL or Aboot is analyzed, thus enabling the new flash memory access command and the new flash memory read command to be analyzed. 
     Further, partition information is analyzed in compliance with the flash memory read command at step S 1030 . 
     Recent smart devices mainly use a package structure in which NAND flash memory, called an Embedded Multi Media Card (Emmc), and a controller are integrated, and efficiently manage stored data using a file system, such as Yet Another Flash File System (YAFFS) or External File system (EXT)  3 / 4 . Further, partitions such as BOOT, RECOVERY, SYSTEM, and USERDATA are mounted and used in smart devices using a partition function. To acquire data from such flash memory, information about the partitions of the flash memory is required. 
     Each smart device may access the partition signature of the flash memory using a flash memory read command, and may analyze the types of partitions using the partition signature. 
     Here, the types of partitions may include a Master Boot Record (MBR), a GUID Partition Table (GPT), etc. 
     The partition table values corresponding to the partitions are parsed, so that the size of the flash memory, the names of the partitions, the address at which each partition starts, and the address at which each partition ends may be analyzed. 
     The results of analysis may be output via an output unit, and are illustrated in  FIG. 7 . Referring to  FIG. 7 , the total number of partitions, the names of the partitions, and the start addresses and end addresses of the partitions are illustrated. 
     Further, the dump of the flash memory is performed and the forensic data is acquired based on the flash memory read command and the analyzed partition information at step S 1040 . 
       FIG. 11  is an operation flowchart showing the procedure in which the smart device enters a firmware update mode in the forensic data acquisition method according to an embodiment of the present invention. 
     Referring to  FIG. 11 , whether the system of the smart device is powered on is determined at step S 1011 . If it is determined that the system is powered on, the system is terminated at step S 1012 . 
     Further, after the system has been terminated or when the system is powered off, the smart device is booted in a firmware update mode at step S 1013 . 
     Here, the smart device may enter the firmware update mode via the manipulation of a button key in the state in which the system is powered off. 
     To enter the firmware update mode, the smart device may enter the firmware update mode using resistance between pins 4 and 5 of a USB cable for connecting the smart device to the forensic data acquisition apparatus. 
     In the case of the USB cable, the access mode may differ depending on the resistance between pins 4 and 5. That is, the smart device may enter the firmware update mode depending on the resistance between pins 4 and 5. For example, when the resistance between pins 4 and 5 is 300 KΩ, a specific smart phone may enter the firmware update mode. When the resistance between pins 4 and 5 is 910 KΩ, another smart phone may enter the firmware update mode. That is, the command analysis unit  110  may determine the resistance between pins 4 and 5 of the USB cable for connecting the smart device that desires to enter the firmware update mode to the forensic data acquisition apparatus, and may control the USB cable based on the determined resistance, thus entering the firmware update mode. 
     The scheme for entering the firmware update mode may differ for each smart device. Referring to  FIG. 4 , the scheme for entering the firmware update mode may differ for each model. For example, to enter the firmware update mode in High-Tech Computer (HTC)&#39;s model, shown in  FIG. 4 , a method of simultaneously pressing a volume-down key and a power key may be used. However, to enter the firmware update mode in Samsung&#39;s Galaxy, a method of simultaneously pressing a volume-down key, a home key, and a power key or of utilizing a USB cable having 300 KΩ may be used. 
     Further, whether the smart device is a model in which a dump function is supported is determined at step S 1014 . If the smart device is found to be a model in which a dump function is not supported, the firmware update protocol is analyzed at step S 1015 . 
       FIG. 12  is an operation flowchart showing the procedure for analyzing partition information in the forensic data acquisition method according to an embodiment of the present invention. 
     Referring to  FIG. 12 , partition information to be analyzed is acquired at step S 1031 , and partition types are analyzed using a flash memory read command and a partition signature at step S 1032 . 
     Further, partition table values are parsed at step S 1033 , and the size of the flash memory, the names of partitions, and the start and end addresses of the partitions are analyzed at step S 1034 . 
     Here, the results of analysis may be output via the output unit, and are shown in  FIG. 7 . Referring to  FIG. 7 , the total number of partitions, the names of the partitions, and the start and end addresses of the partitions are illustrated. 
       FIG. 13  is an operation flowchart showing the procedure for dumping flash memory in the forensic data acquisition method according to an embodiment of the present invention. 
     Referring to  FIG. 13 , whether to dump the whole flash memory (entire contents of the flash memory) is selected at step S 1041 . 
     Here, it is possible to select any one of a whole flash memory dump mode, in which the entire contents of flash memory are dumped, and a partition dump mode, in which the contents of partitions in the flash memory are dumped. When the whole flash memory dump mode is selected, a dump may be performed at the selected dump image generation location in units of sectors of the flash memory. Meanwhile, when the partition dump mode is selected, a dump is performed at the dump image generation location corresponding to each partition in units of sectors in the partition, and then a dump image may be generated. In the present invention, in the firmware update mode in which only the boot loader and the USB module are activated, an image may be physically dumped. As a result, even if data is repeatedly acquired multiple times, the integrity of the data may be maintained without falsifying original evidentiary data. 
     Here, if the whole flash memory is to be selected, the size and dump time of the whole flash memory are calculated at step S 1042 . 
     Next, the location at which a dump image is to be generated is selected at step S 1043 , and a dump procedure is performed in units of sectors at step S 1044 . The dump procedure is performed until the entire contents of flash memory have been dumped. 
     Further, when the entire contents of flash memory have been dumped at step S 1045 , a hash value for the acquired dump image is generated at step S 1051 , and the results of the dump and the hash value are output at step S 1052 . 
     In this case, to verify the integrity of the acquired data, the forensic data acquisition apparatus may further include an integrity verification unit (not shown) for generating a hash value using data and a hash function and verifying the integrity of data using the hash value. Since the hash function may be generally used to verify the integrity of data, the present invention uses a hash function to verify the integrity of the acquired data (forensic data). 
     Here, if it is determined that the whole flash memory is not selected, the partitions to be dumped are selected at step S 1046 , and the size and dump time of each partition are calculated at step S 1047 . 
     Further, the locations at which dump images are to be generated for respective partitions are selected at step S 1048 , and a dump procedure is performed in units of sectors at step S 1049 . The dump procedure continues to be performed until the all of the selected partitions have been dumped. 
     Furthermore, when all of the selected partitions have been dumped at step S 1050 , hash values for the acquired dump images are generated at step S 1051 , and dump results and hash values are output at step S 1052 . 
     In this case, to verify the integrity of the acquired data, the forensic data acquisition apparatus may further include an integrity verification unit (not shown) for generating a hash value using data and a hash function and verifying the integrity of data using the hash value. Since the hash function may be generally used to verify the integrity of data, the present invention uses a hash function to verify the integrity of the acquired data (forensic data). 
     As described above, the present invention acquires forensic data by activating only a boot loader and a USB module in a smart device that contains evidence, thus enabling evidentiary data to be acquired without damaging the smart device that contains the evidence. 
     Further, the present invention performs an operation in a firmware update mode so as to activate only a boot loader and a USB module in the smart device, thus acquiring forensic data while guaranteeing the integrity of flash memory. 
     As described above, in the forensic data acquisition apparatus and method according to the present invention, the configurations and schemes in the above-described embodiments are not limitedly applied, and some or all of the above embodiments can be selectively combined and configured so that various modifications are possible.