CSteg: Talking in C code

Abstract

Cryptographic software has suffered in many ocassions from export restrictions. Governments might claim that cryptographic algorithms are equivalent to military equipment to justify and maintain these restrictions. Sometimes, these laws are approved under dictatorial rules or even by democratric goverments which exploit and overstimate a terrorist menace to restrict civil rights. Citizens have evaded these restrictions in many ways: handwriting the program's source code and then typing it again, printing the source code in a t-shirt, using some kind of steganographic technique, etc. In this paper, we present a system called CSteg that hides source code into plain text by using context-free grammars. This presents the additional advantage that under some laws plain text is protected (and its exportation allowed) by free-speech and/or intellectual property legislation.