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Perhaps in childhood you sorted out all sorts of things to find out how they were made – for which you probably flew. For adult uncles, such entertainment is also not alien, and it is called "reverse engineering", or "reverse engineering." We at Hacker periodically write about software reverse, but hardware reverse is no less interesting. In this article, you will learn about current methods of reversing printed circuit boards and how developers counteract it.
The formal definition of reverse engineering is as follows: this is the process of restoring the circuit and identifying components in the absence of a complete set of documentation. Why is this necessary if you are not eight years old and you have a disassembled father’s laptop in front of you? As a rule, to steal the circuitry of an attractive device and sell it to some manufacturer or pass it off as your own. Less often – to improve and establish the release of an analogue.
Reverse engineering also allows you to identify key circuit elements that will allow access, for example, to JTAG circuits, boot ROM or RAM. Or the goal may be to introduce hardware trojans that change the device’s functions, for example, to turn an external drive into a killer flash drive, and an HDMI cable into a means of analyzing the contents displayed on the screen.
Techniques similar to those used for printed circuit boards can be used to restore the structure of microassemblies or even microcircuits.
Hardware reversing has come a long way from direct copying to automated high-tech circuit board circuitry recovery. Many companies are ready to help anyone with this, it is worth paying them with a minted coin.
Fundamentals of hardware reverse engineering
So, a printed circuit board is usually a multi-layer sandwich of electrically conductive and insulating layers, a solder mask and a finish coat on which electronic components are mounted. Most often, the goal of the reverser is to restore the circuit board. But the process does not begin with this, but with opening and disassembling the case, identification of components and connections between them. At each of these stages, there are difficulties.
Reverse engineering is divided into destructive (after which the printed circuit board ceases to work, but you become the owner of exhaustive information about its structure) and non-destructive – when no one knows about the attempts of reverse engineering.
An autopsy will show
To work with the printed circuit board itself, you do not need as much equipment as it might seem. At first, a camera or smartphone with a good camera and a multimeter will come in handy.
But when parsing, there can be many different obstacles – from ingenious latches and screws with non-standard slots (for example, Torx) to very bad factory dirty things like filling boards and components with glues and compounds. It also happens that you have to deal with the results of ultrasonic welding.
Specialists usually have a solid set of tools at hand. As an example, you can see iFixit products, and "Aliexpress" is littered with cheaper counterparts. In extreme cases, special tools are made using 3D printing.
If glue is encountered during parsing, then this is not a reason for a big frustration: as a rule, you can heat it and disconnect everything that has been glued. And ultrasonic welding is not a sentence. It usually does not give great strength, so the seams can be tried locally to cool or try to disconnect mechanically.
And of course, don’t forget to look at YouTube to see if someone has taken apart such a device before you. This will save a lot of effort and time, as well as seriously reduce the likelihood of something to be damaged.
On the left is the opening of the Xbox One, in the center is a set of bits for opening the electronic equipment, on the right is the use of a hot air gun for dismantling.
Oddly enough, despite the huge variety of components produced by modern industry, understanding their purpose is not the most difficult task. If there is a marking on the board, you can determine the type of component (chip resistor, chip capacitor, chip inductance, diode, etc.) by name and try to evaluate its rating.
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