Obsfuscate strings in the executable file

marozsas · 07-18-2019, 08:39 PM

I'm writing a C code with sensitive text information on it, that can easily revealed through the Unix util "strings".

How can I obfuscate theses texts in the code?

I thought in a reversible cypher like rot13 but I would like to hear the more experienced fellows.

Cheers,

dugan · 07-18-2019, 09:57 PM

From what I'm seeing on my google search: your idea is actually how it's done.

ntubski · 07-22-2019, 10:12 PM

Quote:

Originally Posted by marozsas

I'm writing a C code with sensitive text information on it

Code should not contain sensitive information. But if you do persist with this anyway,

Quote:

I thought in a reversible cypher like rot13 but I would like to hear the more experienced fellows.

The problem with rot13 is that the result will still be recognized as a string by the "strings" program. It would be better to use a transformation that changes the text into arbitrary bytes.

rnturn · 08-06-2019, 11:38 AM

Quote:

Originally Posted by marozsas

I'm writing a C code with sensitive text information on it, that can easily revealed through the Unix util "strings".

How can I obfuscate theses texts in the code?

I thought in a reversible cypher like rot13 but I would like to hear the more experienced fellows.

Cheers,

You could invert the bits in each character: "A" = 0x41 -> 0xBE == "some odd line drawing character (probably) when displayed". You'd have to define all of your "sensitive" text strings as arrays of hex values that are run through the inversion function before display. Seems like you'll want to write a standalone program to read the strings you wish to be shrouded in your program and returns the C-code needed to define the strings in your source code.

HTH...

bigearsbilly · 08-30-2019, 06:00 AM

You could compress them, overkill maybe but quick and simple enough.
(I think zlib is used in the kernel?)

https://www.zlib.net/manual.html#Utility