There's this web proxy called SilverTrash.com Its unblockable! If you look at the source its encrypted. What type of encryption is it?
Maybe it's unblockable because it uses a secure connect (https) though my Firefox won't let me access it due to the security certificate not being trustable (it's self-signed and expired). I don't feel like adding an exception so I can't check out their encryption but I thought I'd post anyways to say that usually by using https, it can avoid being blocked.
More advanced web filters can block IP addresses and SSL ports. I'm actually wondering if there is a way to make it so that if a filtering program comes around and tried to view/categorize your website, you either redirect it to a "safe" website or somehow "block it"
Well, since you said its source is encrypted, it's possible that those programs/filters don't know to block it because they can't see the keywords in the source that they're looking for to know it's a proxy.