Reverse engineering
Reverse engineering (RE) is the process of discovering the technological principles of a mechanical application through analysis of its structure, function and operation. It often involves taking something (e.g., a mechanical
device, an
electronic component, a
software program) apart and analyzing its workings in detail, usually with the intention to construct a new device or program that does the same thing without actually copying anything from the original. The
verb form is
to reverse-engineer.
A telling analogy of RE is that the research of
physical laws can be seen as reverse-engineering the world itself.
Under United States law, reverse engineering a
patented item can be
infringement; however, if the artifact or process is protected by
trade secrets instead of by a patent, then reverse-engineering the artifact or process is lawful as long as the artifact or process is obtained legitimately. In fact, one common motivation of reverse engineering is to determine whether a competitor's product infringes on your patents.
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,
white 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 usuable format such as a triangular faced mesh, a set of NURBS surfaces or a CAD model. Applications like Imageware, Rapidform or Geomagic are used to process point the point clouds themselves into formats usable in other applications such as 3D CAD, CAM, CAE or visualization.
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 WWII include:
*
Jerry can: British and American forces noticed that the Germans had gasoline cans with an excellent design. They reverse engineered copies of those cans. The cans were popularly known as
Jerry cans.
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Tupolev Tu-4: A number of American
B-29 bombers on missions over
Japan were forced to land in the
USSR. The Soviets, who did not have a similar strategic bomber, decided to copy the B-29. Within a few years they had developed the Tu-4, a near perfect copy.
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.
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 his 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.
Reverse engineering is also used by businesses to bring existing physical geometry into digital product development environments, to make a digital 3D record 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 analysing products, but the objective is to find opportunities for cost cutting.
Finally, reverse engineering often is done because the documentation of a particular device has been lost (or was never written), and the person who built the thing is no longer working at the company. Integrated circuits often seem to have been designed on obsolete, proprietary systems, which means that the only way to incorporate the functionality into new technology is to reverse-engineer the existing chip and then re-design it.
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. From their paper:
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).
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.
Binary software
This process is sometimes termed
Reverse Code Engineering or RCE.
As an example, decompilation of binaries for the
Java platform can be accomplished using
ArgoUML. One famous case of reverse engineering was the first non-
IBM implementation of
BIOS which launched the historic
PC clone industry.
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.
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.
Binary software techniques
Reverse engineering of software can be accomplished by various methods. The three main groups of software reverse engineering are:
#Analysis through observation of information exchange, most prevalent in protocol reverse engineering, which involve using
bus analyzers and
packet sniffers for example for listening into a
computer bus or
computer network connection, revealing the traffic data underneath. Behaviour on the bus or network can then be analyzed for producing a stand-alone implementation that mimics the same behaviour. This is especially good for reverse engineering of
device drivers. Sometimes reverse-engineering on
embedded systems is greatly helped by tools deliberately introduced by the manufacturer, such as
JTAG ports or other debugging means. In
Microsoft Windows low-level debuggers such as
SoftICE are popular.#
Disassembly using a
disassembler, meaning the raw
machine language of the program is read and understood in its own terms, only with the aid of machine language
mnemonics. This works on any computer program but can take quite some time, especially for someone not used to machine code.#Decompilation using a
decompiler, a process that tries, with varying result, to recreate the source code in some high level language for a program only available in machine code or bytecode.
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Antikythera mechanism: a famous example of Reverse engineering.
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Clean room design*
Decompiler*
Digital Millennium Copyright Act*
Interactive Disassembler*
Value engineering*
List of production topics*
Forensic engineering*
Program transformation wiki on Reverse Engineering*
Reverse Code Engineering, as entry point for Reverse Code Engineering
*
Introduction to Reverse Engineering Software, preprint of a book by
Mike Perry and
Nasko Oskov.
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Reverse Engineering Shapes, article by
Tamás Várady*
Online Resource for Reverse Engineering Software*
Article on legal considerations by
David C. Musker*
CNN: How Soviets copied America's best bomber during WWII
