Understanding Adobe ACSM
As I understand it, the idea of the acsm file is to give information to ADE so that it can pass your public key to Adobe (or whoever is hosting the ebook) which will take the key, encrypt the book, then download it to ADE.
The acsm file is an XML file, and contains the url of the ebook. I purchased a book looked at the acsm file (which never went near ADE as it is not installed), and downloaded the epub file mentioned in the acsm from the site I bought the book from. I was expecting that the book wouldn't have been at the download location until the key was sent, but it was.
So this epub book isn't encrypted with my key, as I don't have one. It is encrypted of course, but with what?