Compressing a huge paper for a double blind review process
The real problem with such a paper is that conferences have deadlines. Therefore the review process needs to be expeditious. Journals can in most cases handle long papers since they don't need to promise when the paper will appear and try to have a big enough backlog that they can fill an issue with interesting work. But if the call asks for 10 page papers that is what they really are depending on. 

I don't think the "method" by which you make the longer work available is the issue. You can probably find a way to make it blind. But the length isn't copacetic for purposes of their very hard deadlines. 

For the conference, write something else. Or write some small excerpt of the longer work that fits the expectations of the committee. 

But if you prove a long standing and important theorem, a short, even one page, announcement is probably enough for a conference, ending with "Proof will follow." You will want to include some information about why you think your proof stands up  - vetting by some other folks. If you want to get bold, mention the key element of the proof (the crux) that made it come together. Now you are up to around, say, 10 pages. All is good. The full proof can appear later in a more appropriate journal.