Using CrossBridge/FlasCC for Code Obfuscation

One advantage of using CrossBridge is that, because your source code is written in C/C++, it's very hard to decompile.Although some decompilers can give you the decompiled ActionScript code from the swf file, it is impossible to recover the original C/C++ source code. What's more, the decompiled ActionScript code is almost unreadable.

See what the official CrossBridge document says：

FlasCC is not designed to be an obfuscator for either ActionScript or C/C++ code. Although the generated ActionScript bytecode should be no easier to reverse engineer than natively compiled machine code the FlasCC engineering team makes no strong claims about this, nor do they test whether this is true.
By default the mangled C++ name of every source function will be trivially visible in both the decompiled output and also in ActionScript debugger and profilers. To hide the names of any generated C/C++ functions you can pass -fllvm-opt-opt=-strip to gcc so that any function names not listed in your exports.txt file will be renamed to a symbol of the form __unnamed_N. Functions that need to be called from ActionScript, which you must protect by listing in exports.txt, will not be renamed.

So to ensure the encryption strength of CrossBridge, you can just pass the option "-fllvm-opt-opt=-strip" to gcc when compiling, this will obfuscate all the function names. By the way, it's possible to use some C/C++ source code obfuscators first before compiling with CrossBridge.

Links: 
https://forums.adobe.com/message/5121420
http://hecool108.blogspot.com/2013/08/hide-your-key-with-alchemyflascccrossbr.html