## 2 Related Works and State of the Art Review
### Tools and Software for Smartphone Repairing
#### 2.3.1 In-System Programming  
In-System Programming (ISP) is a technique already used for forensic analysis of mobile devices. However, in this article, we will discuss its use not only for reading data from the device's main memory, but also for writing data, changing partitions of the device's main memory, it is considered that--to the best of the authors' knowledge and until the elaboration of this work--it is a possibility not yet explored. Its use will not be as a main tool, but as a component of a methodology that combines the use of other tools for the successful acquisition of data. According to [PERSON] and [PERSON] [PERSON] and [PERSON] (2018), The forensic analysis using the ISP technique is a less invasive or destructive variation than the Chip-Off technique. The ISP technique involves an advanced acquisition process between the Joint Test Action Group (JTAG) and the Chip-Off. According to [PERSON] (2018), ISP is an acquisition technique similar to JTAG, but faster because its connection is made directly to flash memory, bypassing the processor, through Test Access Points (TAPs), and can be used when the device is not compatible with JTAG. ISP acquisition applies to an eMMC or eMCP flash memory, not limited to smartphones only, and can be used on any device that uses these types of memories, such as SD cards. In ISP, it is necessary to know the TAPs that connect to the flash memory. It is necessary to use the Box to connect the computer, where the software will run, with the device board. There are several Box models on the market with the ability to run ISP, the most well known being Easy JTAG Plus and Z3X Pro. For the ISP technique, during the acquisition process, the contents of the internal memory are copied without removing the chip. To the best of the authors' knowledge, to date, ISP acquisition is only available for devices that use flash memory as Embedded Multimedia Card (eMMC) or Embedded Multi-Chip Package (eMCP) with Ball Grid Array (BGA) encapsulation type. In more detail, running the ISP is a process that requires several steps. First, connect the flash memory access taps to an adapter. Second, weld one end of a metallic conductor to the TAP and the other end to the adapter. Third, the TAPs are connected to the Box. The software of the Box provides the TAPs diagram for most smartphones. There are also specialized sites that make these images available. Figure 4 shows the solders on the adapter and the TAPs on the board. The use of the ISP technique allows another analyst to reproduce or repeat all steps of the process for data acquisition since the device remains functional and with all the components on the board. However, even when the Chip-Off technique is applied is possible to return the component to its original location and made to device run again, doing the component soldering process, known as reballing. It is also possible to make use of an interface called VR-TABLE, which has articulated arms, equipped with high-precision metal probes, which dispense the welding of the conductors on the mobile device board, eliminating the possibility of damage caused by overheating. Figure 5 demonstrates the use of a VR-Table. The software of the Box is capable of performing reading/writing operations directly on the eMMC. After soldering all the necessary conductors, the Box is connected to the computer using a USB cable. After completing this step, it is necessary to select the correct software to be used and  
Figure 4: Board ready to run ISP. to configure the necessary parameters. When everything is connected and the software with the parameters correctly configured, the Box can then access or manipulate the content of the memory. Running the ISP, it is possible to manipulate the data using 1 or 4-bit bandwidths. The most common is the use of the value \"1 bit\" because it is less susceptible to errors during copying and because it reduces the exposure of the board to heat since for execution with \"4-bit\" bandwidth, it is necessary to weld 3 more conductors.