Isn't that exactly what Usenet does? Multiple randomly named rar files (usually just numbered, sent over strong SSL). Besides, don't forget that downloading is a CIVIL infringement, it's uploading/sharing that attracts the criminal charges.
The way the CIVIL bodies prove you're sharing is to catch your IP on public torrent/p2p nodes. To actually intercept my SSL certificate from a download server, in order to break any encryption I'm using, they'd need a court order based on criminal allegations.
RIPA (Regulation of Investigatory Powers Act) et al. strongly prevents them from intercepting any of my traffic for such uses - especially for a simple civil infringement! Actually to wiretap my connection like that (sniffing SSL certs, breaking encryption) without said court order and criminal juristiction (police etc) would cause a multitude of criminal acts (Computer Misuse Act, Wireless Telegraphy Act...).
They can't just say "Hey we think Mr X is downloading pr0n from Usenet" and decide to sniff, capture and decode your traffic like that. Not in the UK anyway lol