Is it possible to decompile an Android .apk file?

Are the users able to convert the apk file of my application back to the actual code?

yes.

People can use various tools to:

  • analysis: your apk
  • decode/hack your apk
    • using FDex2 to dump out dex file
      • then using dex2jar to convert to jar
        • then using jadx to conver to java source code

If they do - is there any way to prevent this?

yes. Several (can combined) ways to prevent (certain degree) this:

  • low level: code obfuscation
    • using Android ProGuard
  • high level: use android harden scenario
    • such as
    • Tecent Legu=腾讯乐固
    • qihoo 360=360加固宝

More details can refer my Chinese tutorial: 安卓应用的安全和破解


First, an apk file is just a modified jar file. So the real question is can they decompile the dex files inside. The answer is sort of. There are already disassemblers, such as dedexer and smali. You can expect these to only get better, and theoretically it should eventually be possible to decompile to actual Java source (at least sometimes). See the previous question decompiling DEX into Java sourcecode.

What you should remember is obfuscation never works. Choose a good license and do your best to enforce it through the law. Don't waste time with unreliable technical measures.


Decompilation of APK file is possible. But it might be difficult to understand the code if it is obfuscated.

Use Aapt (part of the Android SDK) or AXMLParser (from AndroGuard) to analyse and view info of an APK File

  • Retrieves the content of the AndroidManifest.xml file

  • Shows various information (e.g. permissions, activities, services, broadcast receivers, ...)

  • Command:

    Aapt

     aapt dump badging sampleApp.apk
 aapt dump permissions sampleApp.apk
 aapt dump xmltree sampleApp.apk

    AXMLParser

     apkinfo sampleApp.apk

Use ApkTool or NinjaDroid to disassemble and view the resources of an APK File

  • Disassembles the bytecode to smali/assembly

  • Extracts the AndroidManifest.xml, the CERT.RSA file and everything in res folder (layout xml files, images, htmls used on webview etc..)

  • Command:

    ApkTool

    apktool.bat d sampleApp.apk

java -jar apktool.jar -q decode -f sampleApp.apk -o myOutputDir

    NinjaDroid

    ninjadroid MyApk.apk --all --extract myOutputDir/

  • NOTE: You can achieve something similar by using zip utility like 7-zip. But, these tools also extract the .smali files of all .class files.

Use dex2jar to decompile the DEX files of an APK File into Java code

  • Generates the .jar file from a .apk file (note that the Java code of Android apps is usually obfuscated)

  • Needs JD-GUI to view the source code from the output .jar file

  • Command:

    dex2jar sampleApp.apk

d2j-dex2jar.sh -f sampleApp.apk -o myOutputDir/sampleApp.jar

Use JD-GUI to view the .jar file

  • Decompiles the .class files (obfuscated in a case of Android apps, but not in a case of other .jar files) and shows the corresponding Java code

I may also add, that nowadays it is possible to decompile Android application online, no software needed!

Here are 2 options for you:

  • http://www.decompileandroid.com/
  • http://www.javadecompilers.com/apk

Tags:

Obfuscation

Android

Decompiling

Dex

Apk

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