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Home > Obfuscated code

2.1 Uses for obfuscation

2.1.1 Makes reverse engineering more difficult

Even when a language is compiled to an executable or bytecode file, someone may choose to run a decompiler which converts these files back into human-readable form (generally without comments).

This could help them understand whatever lies hidden within the source code, against the wishes of the code's creator.

Obfuscation serves to increase the difficulty of decompilation, usually forcing someone who wants that information to use more costly forms of reverse engineering.

2.1.2 Minimizes code size

Obfuscation usually breaks down structures which make programs modular and maintainable. This has the pleasant side-effect of reducing code size in many cases. For example, in dynamic languages that incorporate a symbol table with the executable code, simple variable renaming can save a great deal of space in the resulting code footprint. This is a crucial consideration if code size must be kept to a minimum, as with code that must be sent over a network or embedded into a small device.

2.1.3 Concealment of evidence

Dealers in spamming software have sold JavaScript obfuscators for the purpose of confounding investigators. Some of the techniques use JavaScript's dynamic nature -- a piece of code is stored as an encrypted string, which is decrypted and evaluated. This may be done several times. Other techniques include insertion of dummy code, as well as dummy HTML links to legitimate pages.

2.2 Disadvantages of obfuscation

2.2.1 Debugging

Obfuscated code is extremely difficult to debug. Variable names will no longer make sense, and the structure of the code itself will likely be modified into unrecognizability. This fact generally forces developers to maintain two builds: One that can be easily debugged, and another for release. Both builds should be tested to make sure they act identically.

2.2.2 Portability

Obfuscated code often depends on the particular characteristics of the platform and compiler making it difficult to manage if either change.

2.2.3 Defective obfuscators

Occasionally an obfuscator may be buggy, in a difficult to reproduce way. There is little one can do except find or create a newer version or fiddle with any inputs to the obfuscator until it magically works.

2.2.4 Conflicts with Reflection APIs

Many obfuscators allow specified classes to be exempt from renaming; and it is also possible to let a class be renamed and call it by its new name. However, the former option places limits on the dynamism of code, while the latter adds a great deal of complexity and inconvenience to the system.

3 External links

• IBM's Java Obfuscator
• Analysis of the 12 days program
• Analysis of the obfuscated maze generating program
• Obfuscated Perl program with explanation

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Obfuscated codeObfuscated code is source code that is (perhaps intentionally) very hard to read and understand. Some languages are more prone to obfuscation than others. C, C++ and Perl are most often cited as easily obfuscatable languages. Macro preprocessors are often Obfuscated Perl contestThe Obfuscated Perl contest is a competition for programmers of Perl which has been held annually since 1996. Entrants to the competition aim to write "devious, inhuman, disgusting, amusing, amazing, and bizarre Perl code" . The competition is divided int