I study chaos-based communication systems and one of their main advantages stated in the literature is that they are "secure". But I haven't found any proof of this affirmation in any sense so far.
Hi Marcio, I responded to a similar question in another post. Did you see this article yet? I've attached the link in the file below. Read the comments at the end of the article too. They are informative.
As I replied to the other post, I think that ultimately the vulnerability of these schemes will be in guessing the key, or the initial conditions. Chaos makes no difference, really, because if the process is not reversible, the encryption becomes useless. If chaos theory tells us that the intermediate steps are determinstic, then I'm not sure what that adds in terms of security!