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Reverse engineering, also called back engineering, is the process by which a man-made object is deconstructed to reveal its designs, architecture, or to extract knowledge from the object; similar to scientific research, the only difference being that scientific research is about a natural phenomenon. 3:
Reverse engineering is applicable in the fields of mechanical engineering, electronic engineering, software engineering, chemical engineering,and systems biology.
There are many reasons for performing reverse engineering in various fields. Reverse engineering has its origins in the analysis of hardware for commercial or military advantage. 13 However, the reverse engineering process, as such, is not concerned with creating a copy or changing the artifact in some way; it is only an analysis in order to deduce design features from products with little or no additional knowledge about the procedures involved in their original production. :15 In some cases, the goal of the reverse engineering process can simply be a redocumentation of legacy systems. :15 Even when the reverse-engineered product is that of a competitor, the goal may not be to copy them, but to perform competitor analysis. Reverse engineering may also be used to create interoperable products and despite some narrowly tailored United States and European Union legislation, the legality of using specific reverse engineering techniques for this purpose has been hotly contested in courts worldwide for more than two decades.:
Software reverse engineering can help to improve the understanding of the underlying source code for the maintenance and improvement of the software, relevant information can be extracted in order to make a decision for software development and graphical representations of the code can provide alternate views regarding the source code, which can help to detect and fix a software bug or vulnerability. Frequently, as some software develops, its design information and improvements are often lost over time, but this lost information can usually be recovered with reverse engineering. This process can also help to cut down the time required to understand the source code, reducing the overall cost of the software development. 7 or to create a (possibly improved) copy or even a knockoff, which is usually the goal of a competitor or a hacker. :8 Malware developers often use reverse engineering techniques to find vulnerabilities in an operating system (OS), in order build a computer virus that can exploit the system vulnerabilities. :5 Reverse engineering is also being used in cryptanalysis in order to find vulnerabilities in substitution cipher, symmetric-key algorithm or public-key cryptography. :6Reverse engineering can also help to detect and eliminate a malicious code written to the software with better code detectors. Reversing a source code can be used to find alternate uses of the source code, such as to detect unauthorized replication of the source code where it wasn't intended to be used, or to reveal how a competitors product was built. This process is commonly used for "cracking" software and media to remove their copy protection, :
In addition to these purposes there are other uses to reverse engineering:
As computer-aided design (CAD) 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 or 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 industrial CT scanning (computed tomography). The measured data alone, usually represented as a point cloud, lacks topological information and design intent. The former may be recovered by converting the point cloud to a triangular-faced mesh. Reverse engineering aims to go beyond producing such a mesh, and to recover the design intent in terms of simple analytical surfaces where appropriate (planes, cylinders, etc.), as well as possibly NURBS surfaces, to produce a boundary-representation CAD model. Recovery of such a model allows a design to be modified to meet new requirements, a manufacturing plan to be generated, etc.
Hybrid modeling is a commonly used term when NURBS and parametric modeling are implemented together. Using a combination of geometric and freeform surfaces can provide a powerful method of 3D modeling. Areas of freeform data can be combined with exact geometric surfaces to create a hybrid model. A typical example of this would be the reverse engineering of a cylinder head, which includes freeform cast features, such as water jackets and high tolerance machined areas.
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 to assess competitors' products. It is used to analyze, for instance, how a product works, what it does, and what components it consists of, estimate costs, and identify potential patent infringement, etc.
Value engineering is a related activity also used by businesses. It involves de-constructing and analyzing products, but the objective is to find opportunities for cost-cutting.
In 1990, the Institute of Electrical and Electronics Engineers (IEEE) defined reverse engineering as "the process of analyzing a subject system to identify the system's components and their interrelationships and to create representations of the system in another form or at a higher level of abstraction", where the "subject system" is the end product of software development. Reverse engineering is a process of examination only: the software system under consideration is not modified (which would make it re-engineering or restructuring). Reverse engineering can be performed from any stage of the product cycle, not necessarily from the functional end product.
There are two components in reverse engineering: redocumentation and design recovery. Redocumentation is the creation of new representation of the computer code so that it is easier to understand. Meanwhile, design recovery is the use of deduction or reasoning from general knowledge or personal experience of the product in order to fully understand the product functionality.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. Another term for this technique is program comprehension. The Working Conference on Reverse Engineering (WCRE) has been held yearly to explore and expand the techniques of reverse engineering. Computer-aided software engineering (CASE) and automated code generation have contributed greatly in the field of reverse engineering.
Software anti-tamper technology like obfuscation is used to deter both reverse engineering and re-engineering 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 copyright infringement.
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 chip-sets), or even mere satisfaction of curiosity.
Binary reverse engineering is performed if source code for a software is unavailable.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. 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 free software (GPL) counterpart. WindowsSCOPE allows for reverse-engineering the full contents of a Windows system's live memory including a binary-level, graphical reverse engineering of all running processes.
Another classic, if not well-known, example is that in 1987 Bell Laboratories reverse-engineered the Mac OS System 4.1, originally running on the Apple Macintosh SE, so they could run it on RISC machines of their own.
Reverse engineering of software can be accomplished by various methods. The three main groups of software reverse engineering are
Software classification is the process of identifying similarities between different software binaries (for example, two different versions of the same binary) used to detect code relations between software samples. This task was traditionally done manually for several reasons (such as patch analysis for vulnerability detection and copyright infringement) but nowadays can be done somewhat automatically for large numbers of samples.
This method is being used mostly for long and thorough reverse engineering tasks (complete analysis of a complex algorithm or big piece of software). In general, statistical classification is considered to be a hard problem and this is also true for software classification, therefore there aren't many solutions/tools that handle this task well.
A number of UML tools refer to the process of importing and analysing source code to generate UML diagrams as "reverse engineering". See List of UML tools.
Although UML is one approach to providing "reverse engineering" more recent advances in international standards activities have resulted in the development of the Knowledge Discovery Metamodel (KDM). This standard delivers an ontology for the intermediate (or abstracted) representation of programming language constructs and their interrelationships. An Object Management Group standard (on its way to becoming an ISO standard as well), KDM has started to take hold in industry with the development of tools and analysis environments which can deliver the extraction and analysis of source, binary, and byte code. For source code analysis, KDM's granular standards' architecture enables the extraction of software system flows (data, control, & call maps), architectures, and business layer knowledge (rules, terms, process). The standard enables the use of a common data format (XMI) enabling the correlation of the various layers of system knowledge for either detailed analysis (e.g. root cause, impact) or derived analysis (e.g. business process extraction). Although efforts to represent language constructs can be never-ending given the number of languages, the continuous evolution of software languages and the development of new languages, the standard does allow for the use of extensions to support the broad language set as well as evolution. KDM is compatible with UML, BPMN, RDF and other standards enabling migration into other environments and thus leverage system knowledge for efforts such as software system transformation and enterprise business layer analysis.
Protocols are sets of rules that describe message formats and how messages are exchanged (i.e., the protocol state machine). Accordingly, the problem of protocol reverse-engineering can be partitioned into two subproblems; message format and state-machine reverse-engineering.
The message formats have traditionally been reverse-engineered through a tedious manual process, which involved analysis of how protocol implementations process messages, but recent research proposed a number of automatic solutions.Typically, these automatic approaches either group observed messages into clusters using various clustering analyses, or emulate the protocol implementation tracing the message processing.
There has been less work on reverse-engineering of state-machines of protocols. In general, the protocol state-machines can be learned either through a process of offline learning, which passively observes communication and attempts to build the most general state-machine accepting all observed sequences of messages, and online learning, which allows interactive generation of probing sequences of messages and listening to responses to those probing sequences. In general, offline learning of small state-machines is known to be NP-complete,while online learning can be done in polynomial time. An automatic offline approach has been demonstrated by Comparetti et al. and an online approach by Cho et al.
Other components of typical protocols, like encryption and hash functions, can be reverse-engineered automatically as well. Typically, the automatic approaches trace the execution of protocol implementations and try to detect buffers in memory holding unencrypted packets.
Reverse engineering is an invasive and destructive form of analyzing a smart card. The attacker uses chemicals to etch away layer after layer of the smart card and takes pictures with a scanning electron microscope (SEM). 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. The makers of the card try to hide keys and operations by mixing up memory positions, for example, bus scrambling.
In some cases, it is even possible to attach a probe to measure voltages while the smart card is still operational. The makers of the card employ sensors to detect and prevent this attack.This attack is not very common because it requires a large investment in effort and special equipment that is generally only available to large chip manufacturers. Furthermore, the payoff from this attack is low since other security techniques are often employed such as shadow accounts. It is uncertain at this time whether attacks against CHIP/PIN cards to replicate encryption data and consequentially crack PINS would provide a cost-effective attack on multifactor authentication.
Full reverse engineering proceeds in 5 major steps. The first step after images have been taken with a SEM is stitching the images together. This is necessary because each layer can't be captured by a single shot. A SEM needs to sweep across the area of the circuit and take several hundred images to cover the entire layer. Image stitching takes as input these several hundred pictures and outputs a single, properly overlapped picture of the complete layer. Next, the stitched layers need to be aligned. This is because the sample, after etching, cannot be put into the exact same position relative to the SEM each time. Therefore the stitched versions won't overlap in the correct fashion as on the real circuit. Usually three corresponding points are selected and a transformation applied on the basis of this. To extract the circuit structure, the aligned, stitched images need to be segmented. Segmentation highlights the important circuitry and separates it from the uninteresting background and insulating materials. Now, the wires can be traced from one layer to the next and the netlist of the circuit can be reconstructed which contains all information of the circuit.
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Reverse engineering is often used by people in order to copy other nations' technologies, devices, or information that 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 and later include:
Reverse engineering concepts have been applied to Biology as well, and specifically to the task of understanding the structure and function of gene regulatory networks. Gene regulatory networks regulate almost every aspect of biological behavior and allow cells to carry out physiological processes as well as responses to perturbations. Understanding the structure and dynamic behavior of gene networks is therefore one of the paramount challenges of Systems Biology, with immediate, practical repercussions in several applications beyond basic research.There are several methods for reverse engineering gene regulatory networks using molecular biology and data science methods, and these have been generally divided into six classes:
Often, gene network reliability is tested by genetic perturbation experiments followed by dynamic modelling, based on the principle that removing one network node will have predictable effects on the functioning of the remaining nodes of the network.Applications of Reverse engineering gene networks range from understanding mechanisms of plant physiology to highlighting new targets for anticancer therapy.
Reverse engineering applies primarily to gaining understanding of a process or artifact, where the manner of its construction, use, or internal processes is not made clear by its creator.
Patented items do not of themselves have to be reverse-engineered to be studied, since the essence of a patent is that the inventor provides detailed public disclosure themselves, and in return receives legal protection of the invention involved. However, an item produced under one or more patents could also include other technology that is not patented and not disclosed. Indeed, one common motivation of reverse engineering is to determine whether a competitor's product contains patent infringements or copyright infringements.
In the United States even if an artifact or process is protected by trade secrets, reverse-engineering the artifact or process is often lawful as long as it has been legitimately obtained.
Reverse engineering of computer software in the US often falls under both contract law as a breach of contract as well as any other relevant laws. This is because most end user license agreements specifically prohibit it, and U.S. courts have ruled that if such terms are present, they override the copyright law which expressly permits it (see Bowers v. Baystate Technologies). Sec. 103(f) of the DMCA (17 U.S.C. § 1201 (f)) says that a person who is in legal possession of a program, is permitted to reverse-engineer and circumvent its protection if this is necessary in order to achieve "interoperability" — a term broadly covering other devices and programs being able to interact with it, make use of it, and to use and transfer data to and from it, in useful ways. A limited exemption exists that allows the knowledge thus gained to be shared and used for interoperability purposes.
EU Directive 2009/24 on the legal protection of computer programs, which superseded an earlier (1991) directive,governs reverse engineering in the European Union.
Computing is any activity that uses computers to manage, process, and communicate information. It includes development of both hardware and software. Computing is a critical, integral component of modern industrial technology. Major computing disciplines include computer engineering, software engineering, computer science, information systems, and information technology.
Software cracking is the modification of software to remove or disable features which are considered undesirable by the person cracking the software, especially copy protection features or software annoyances like nag screens and adware.
Interoperability is a characteristic of a product or system, whose interfaces are completely understood, to work with other products or systems, at present or in the future, in either implementation or access, without any restrictions.
Computer science is the study of the theoretical foundations of information and computation and their implementation and application in computer systems. One well known subject classification system for computer science is the ACM Computing Classification System devised by the Association for Computing Machinery.
In computer security, a covert channel is a type of attack that creates a capability to transfer information objects between processes that are not supposed to be allowed to communicate by the computer security policy. The term, originated in 1973 by Lampson, is defined as channels "not intended for information transfer at all, such as the service program's effect on system load," to distinguish it from legitimate channels that are subjected to access controls by COMPUSEC.
Software development is the process of conceiving, specifying, designing, programming, documenting, testing, and bug fixing involved in creating and maintaining applications, frameworks, or other software components. Software development is a process of writing and maintaining the source code, but in a broader sense, it includes all that is involved between the conception of the desired software through to the final manifestation of the software, sometimes in a planned and structured process. Therefore, software development may include research, new development, prototyping, modification, reuse, re-engineering, maintenance, or any other activities that result in software products.
In computer networking, Server Message Block (SMB), one version of which was also known as Common Internet File System, is a network communication protocol for providing shared access to files, printers, and serial ports between nodes on a network. It also provides an authenticated inter-process communication mechanism. Most usage of SMB involves computers running Microsoft Windows, where it was known as "Microsoft Windows Network" before the introduction of Active Directory. Corresponding Windows services are LAN Manager Server for the server component, and LAN Manager Workstation for the client component.
The following outline is provided as an overview of and topical guide to software engineering:
Health Level Seven or HL7 refers to a set of international standards for transfer of clinical and administrative data between software applications used by various healthcare providers. These standards focus on the application layer, which is "layer 7" in the OSI model. The HL7 standards are produced by Health Level Seven International, an international standards organization, and are adopted by other standards issuing bodies such as American National Standards Institute and International Organization for Standardization.
Internet security is a branch of computer security specifically related to not only Internet, often involving browser security and the World Wide Web, but also network security as it applies to other applications or operating systems as a whole. Its objective is to establish rules and measures to use against attacks over the Internet. The Internet represents an insecure channel for exchanging information, which leads to a high risk of intrusion or fraud, such as phishing, online viruses, trojans, worms and more.
In computing, syslog is a standard for message logging. It allows separation of the software that generates messages, the system that stores them, and the software that reports and analyzes them. Each message is labeled with a facility code, indicating the software type generating the message, and assigned a severity level.
The Skype protocol is a proprietary Internet telephony network used by Skype. The protocol's specifications have not been made publicly available by Skype and official applications using the protocol are closed-source.
Fault injection is a testing technique which aids in understanding how [virtual/real] system behaves when stressed in unusual ways. This technique is based on simulation's or experiment's result, thus it may be more valid compared to statistical methods.
A decompiler is a computer program that takes an executable file as input, and attempts to create a high level source file which can be recompiled successfully. It is therefore the opposite of a compiler, which takes a source file and makes an executable. Decompilers are usually unable to perfectly reconstruct the original source code, and as such, will frequently produce obfuscated code. Nonetheless, decompilers remain an important tool in the reverse engineering of computer software.
In telecommunications, a proprietary protocol is a communications protocol owned by a single organization or individual.
Sega Enterprises Ltd. v. Accolade, Inc., 977 F.2d 1510, is a case in which the United States Court of Appeals for the Ninth Circuit applied American intellectual property law to the reverse engineering of computer software. Stemming from the publishing of several Sega Genesis games by video game publisher Accolade, which had disassembled Genesis software in order to publish games without being licensed by Sega, the case involved several overlapping issues, including the scope of copyright, permissible uses for trademarks, and the scope of the fair use doctrine for computer code.
A communication protocol is a system of rules that allow two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware, software, or a combination of both.
The following outline is provided as an overview of and topical guide to software development:
Malware analysis is the study or process of determining the functionality, origin and potential impact of a given malware sample such as a virus, worm, trojan horse, rootkit, or backdoor. Malware or malicious software is any computer software intended to harm the host operating system or to steal sensitive data from users, organizations or companies. Malware may include software that gathers user information without permission.
The unauthorised reproduction, translation, adaptation or transformation of the form of the code in which a copy of a computer program has been made available constitutes an infringement of the exclusive rights of the author. Nevertheless, circumstances may exist when such a reproduction of the code and translation of its form are indispensable to obtain the necessary information to achieve the interoperability of an independently created program with other programs. It has therefore to be considered that, in these limited circumstances only, performance of the acts of reproduction and translation by or on behalf of a person having a right to use a copy of the program is legitimate and compatible with fair practice and must therefore be deemed not to require the authorisation of the rightholder. An objective of this exception is to make it possible to connect all components of a computer system, including those of different manufacturers, so that they can work together. Such an exception to the author's exclusive rights may not be used in a way which prejudices the legitimate interests of the rightholder or which conflicts with a normal exploitation of the program.