Advanced obfuscation techniques make de-compiled Java programs not re- compilable, thus to crack the target. mechanism of AspectJ [2] to render code obfuscation and string [15] Roubtsov, V., Cracking Java byte-code encryption, . Difficult to implement. – Of little benefit: The bytecode has to run! • No public/ private crypto offered. – Can it be implemented? • String encryption uses XOR type. string encryption. The latest version was released June 23, [14]. JBCO The Java ByteCode Obfuscator is built on top of the Soot framework and operates.

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Their findings are summarized in two articles:. This cacking for every single usage of strings, only with different methods, which means that we just figured out where strings get deobfuscated.

Protect Your Java Code — Through Obfuscators And Beyond

Name obfuscation is the process of replacing the identifiers you have carefully chosen to your company’s coding standards, such as com. You are commenting using your Twitter account.

I wonder if they hold an internal “obfuscate-decompile” tournament. As the title suggestes, this post will feature a practical example of cracking obfuscated Java code, namely Allatori 4.

Class EncryptionJava. Now, enabling string encryption makes the decompiled code a little bit more, well, cryptic:. That is, until the system administrator account gets hacked. For the signing scheme to be hard to break, the key needs to be inaccessible.

cryptography – Why not encrypt the Java bytecode instead of obfuscate it? – Stack Overflow

Fortunately, there exist a class of tools originally developed with the goal of improving performance of Java applications. Of course, the classes would have been encrypted using the public key of this “unique oracle certificate”.

Standard Posted by boredliner. Dependencies are resolved at run time, when classes are loaded. Thomborson, or the more recent Revisiting Software Protection by P. It measures the performance of numerical computations typically found in scientific and engineering applications. Compiling this class with the standard javac compiler and decompiling the resulting class file using one of the freely available decompilers yields: A higher score is better.


On the other hand, if flow obfuscation has little or no impact on performance, it may be an indicator of obfuscation weakness. A nice side effect of name obfuscation is the substantial reduction of class file size, which results in somewhat smaller downloads and faster cold starts of desktop Java applications, and enables your Android smartphone to hold more apps games.

As long as someone has both the encrypted application and the decryption key, they can obtain the original classes fairly easily regardless of how they were encrypted. But it will make the classloader reaaaally slow. You should really pay attention at this point since zip-archives support case-sensitive filenames for example cG. How about the text of the button shown to the user?

Reverse engineering of your proprietary applications by unfair competition or malicious hackers may result in highly undesirable exposure of your algorithms and ideas, proprietary data formats, licensing and security mechanisms, and, most importantly, your customers’ data. Running the application under a debugger with a breakpoint set on MessageDigest. Email Required, but never shown. An application is delivered as a monolithic executable maybe with a few dynamic librariesso it is not easy to identify all member functions of a given class or reconstruct the class hierarchy.

This, and the fact that Allatori 4. Debug info obfuscation By default, the javac compiler writes source file names and, optionally, line number information with -g option to the resulting class files. But any code designed to run on third-party systems has to include or be accompanied with the respective decryption key and hence may not be protected through encryption.

However, as Java is now open source, one may simply download the OpenJDK source code, patch it to dump loaded classes to disk and force the -XX: If you employ obfuscation to hide them, it becomes less trivial, but it etring still be done. Numerous code optimizations are performed at compile time. Names of serializable classes may not be obfuscated.

Protect Your Java Code – Through Obfuscators and Beyond

Indeed, it is possible to make the result of decompilation much less readable with JBCO. Any person of ordinary skills in programming can download a Java decompilerrun your application through it and read the source code almost as if it was open source.

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Indeed, the obfuscator I was using could only make one change after I enabled code obfuscation: Moreover, in most tools string encryption is so straightforward that the hacker does not even need to reverse-engineer that code! Apache Tomcat in Amazon EC2. The slowdown ranges from 1. What else would you have expected to find at the end of an article on a vendor site, anyway?

If you want to learn more about code and data flow obfuscation techniques and how they rank against each other in terms of potency, resilience and cost, the three-part series by Sonali Gupta, appeared in the Palisade Magazine in Aug-Octwould make a good start:. Relies on dynamic Just-In-Time compilation for performance improvement. Entities accessed via reflection or JNI at run time may not be renamed.

Of course, it would be applicable to concrete cases not eclipse and only sensible classes would be encrypted election of the developer, of course. An application is typically delivered as a set of jar files, which are just non-encrypted archives containing individual class files.

As you may see, the only major differences in the decompiled source code are automatically generated names of parameters and local variables.

The actual obfuscation is more or less the same, but the key used in it is not simply pushed to the stack but calculated using different stack operations. Ramachandran had studied commercial Java Obfuscators. But before I move on, a word of caution:.

So a hacker would still have little doubt over where to look for sensitive code, ij they don’t even need to reverse the encryption algorithm. Class hierarchy, high-level statements, names of classes, methods and fields – all this can be retrieved from class files emitted by the standard javac compiler.