Reverse engineering (RE) is the process of discovering the technological principles of a device, object or system through analysis of its structure, function, and operation. It often involves taking something (for example a mechanical device, electronic component, or software program) apart and analyzing its workings in detail, usually to try to make a new device or program that does the same thing without copying anything from the original.
Reasons for reverse-engineering:
As computer-aided design has become more popular, reverse engineering has become a viable method to create a 3D virtual model of an existing physical part for use in 3D CAD, CAM, CAE and other software. The reverse engineering process involves measuring an object and then reconstructing it as a 3D model. The physical object can be measured using 3D scanning technologies like CMMs, laser scanners, structured light digitizers, or computed tomography. The measured data alone, usually represented as a point cloud, lacks topological information and is therefore often processed and modeled into a more usable format such as a triangular faced mesh, a set of NURBS surfaces or a CAD model. Applications like Imageware, PolyWorks, Rapidform, or Geomagic are used to process the point clouds themselves into formats usable in other applications such as 3D CAD, CAM, CAE or visualization.
Reverse engineering is also used by businesses to bring existing physical geometry into digital product development environments, to make a digital 3D record of their own products or assess competitors' products. It is used to analyze, for instance, how a product works, what it does, what components it consists of, estimate costs, identify potential patent infringement, etc.
Value engineering is a related activity also used by business. It involves deconstructing and analyzing products, but the objective is to find opportunities for cost cutting.
The term "reverse engineering" as applied to software means different things to different people, prompting Chikofsky and Cross to write a paper researching the various uses and defining a taxonomy. According to them, Reverse engineering is the process of analyzing a subject system to create representations of the system at a higher level of abstraction. It can also be seen as "going backwards through the development cycle". In this model, the output of the implementation phase (in source code form) is reverse engineered back to the analysis phase, in an inversion of the traditional waterfall model. Reverse engineering is a process of examination only: the software system under consideration is not modified (which would make it reengineering). Software anti-tamper technology is used to deter both reverse engineering and reengineering of proprietary software and software-powered systems. In practice, two main types of reverse engineering emerge. In the first case, source code is already available for the software, but higher level aspects of the program, perhaps poorly documented or documented but no longer valid, are discovered. In the second case, there is no source code available for the software, and any efforts towards discovering one possible source code for the software are regarded as reverse engineering. This second usage of the term is the one most people are familiar with. Reverse engineering of software can make use of the clean room design technique to avoid infringing copyrights.
On a related note, black box testing in software engineering has a lot in common with reverse-engineering. The tester usually has the API, but their goals are to find bugs and undocumented features by bashing the product from outside.
Other purposes of reverse engineering include security auditing, removal of copy protection ("cracking"), circumvention of access restrictions often present in consumer electronics, customization of embedded systems (such as engine management systems), in-house repairs or retrofits, enabling of additional features on low-cost "crippled" hardware (such as some graphics card chipsets), or even mere satisfaction of curiosity.
This process is sometimes termed Reverse Code Engineering or RCE. As an example, decompilation of binaries for the Java platform can be accomplished using Jad. One famous case of reverse engineering was the first non-IBM implementation of the PC BIOS which launched the historic IBM PC compatible industry that has been the overwhelmingly dominant computer hardware platform for many years. An example of a group that reverse engineers software for enjoyment is CORE, which stands for "Challenge Of Reverse Engineering." In the United States, the Digital Millennium Copyright Act exempts from the circumvention ban some acts of reverse engineering aimed at interoperability of file formats and protocols, but judges in key cases have ignored this law, since it is acceptable to circumvent restrictions for use, but not for access. Aside from restrictions on circumvention, reverse engineering of software is protected in the U.S. by the fair use exception in copyright law. The Samba software, which allows systems that are not running Microsoft Windows systems to share files with systems that are, is a classic example of software reverse engineering, since the Samba project had to reverse-engineer unpublished information about how Windows file sharing worked, so that non-Windows computers could emulate it. The Wine project does the same thing for the Windows API, and OpenOffice.org is one party doing this for the Microsoft Office file formats. The ReactOS project is even more ambitious in its goals as it strives to provide binary (ABI and API) compatibility with the current Windows OSes of the NT branch, allowing software and drivers written for Windows to run on a clean room reverse engineered GPL open source counterpart.
Reverse engineering of software can be accomplished by various methods. The three main groups of software reverse engineering are
A number of UML tools refer to the process of importing source code in order to generate UML diagrams, as "reverse engineering."
Reverse Engineering is an invasive and destructive form of analyzing a smart card. The attacker grinds away layer by layer of the smart card and takes pictures with an electron-microscope. With this technique it is possible to reveal the complete hardware and software part of the smart card. The major problem for the attacker is to bring everything into the right order to find out how everything works. Engineers try to hide keys and operations by mixing up memory positions, for example busscrambling
In some cases it is even possible to attach a probe to direct measure voltages while the smart card is still operational. Engineers employ sensors to detect and prevent this attack. It takes very high effort to break a smart card used for payment, for example, and the technical equipment is only available to large chip-producers. Additionally the gain is low due to other security mechanisms like shadow accounts.
Reverse engineering is often used by military in order to copy other nations' technology, devices or information, or parts of which, have been obtained by regular troops in the fields or by intelligence operations. It was often used during the Second World War and the Cold War. Well-known examples from World War II and later include:
In the United States and many other countries, even if an artifact or process is protected by trade secrets, reverse-engineering the artifact or process is often lawful as long as it is obtained legitimately. Patents, on the other hand, need a public disclosure of an invention, and therefore patented items do not necessarily have to be reverse engineered to be studied. One common motivation of reverse engineers is to determine whether a competitor's product contains patent infringements or copyright infringements.
Reverse engineering software or hardware systems which is done for the purposes of interoperability (for example, to support undocumented file formats or undocumented hardware peripherals), is mostly believed to be legal, though patent owners often contest this and attempt to stifle any reverse engineering of their products for any reason.
"…[W]here disassembly is the only way to gain access to the ideas and functional elements embodied in a copyrighted computer program and where there is a legitimate reason for seeking such access, disassembly is a fair use of the copyrighted work, as a matter of law."
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