iTunes - Authorization is needed to access ....

The link you give gets a 'file not found' error.

The iTunes Store expects to be able to access and play the media file without issues - the test is that if you paste the URL into a browser it will play in the browser. And of course when people subscribe they download the file: you are not allowed to password protect it. If you've got any sort of security setup iaccess it's not going to work in iTunes.

It's not really possible to comment further than that unless you would like to publish the URLs of both your feed and the Store page - if you've got that far; this can be found by control-clicking on the podcast image - or where it should be - and choosing 'Copy link'. Please include the http:// in both cases to make the links clickable.

As you haven't explained 'with some extra parameters so that my CDN can protect the file from illegal downloads' nor provided any other information I can't really add anything to what I've already said - except to notice that your demonstration URL doesn't include the .mp3 extension - iTunes requires this in the feed to know what sort of file it's dealing with.

(If you don't want to post the feed that's entirely your decision, of course: but if you have a podcast in the iTunes Store anyone can get the feed URL in 5 seconds, so it's hardly a secret.)

A further look shows the .mp3 extension buried in the middle - apparently you're using PHP or similar to serve up the file. This won't work; you need a direct link to the file itself.