How to hide download links by recaptcha?

How can I hide a download link by recaptcha ?

I mean that if someone visits my blog post, He should solve a captcha to see the div containing download link.

I've searched but I couldn't find anything.

There's a tutorial here :

http://ift.tt/1BSa9jQ

But that's for login & comment forms. How can I do that for a custom div in my theme ?

via Chebli Mohamed