I'm pretty sure Blitz Media Linker encrypts the data, while it compresses it. I don't think it will be an easy job for anyone to get your media if you use BML.
There are a few other options available here: http://www.blitzbasic.com/toolbox/toolbox.php?cat=10
There are a few other options available here: http://www.blitzbasic.com/toolbox/toolbox.php?cat=10