Re: Citation needed
Encryption to specific recipients and groups, and serving files off one's own machine are perhaps going to get more interesting.
It's easier than that. Use a public hosting firm that lets you configure TLS. Run your own CA (it can be a toy/demo CA like OpenSSL's) and issue client certificates to anyone you want to grant access. Leave index pages and their resources unrestricted, but require a client certificate for anything you don't want visible to hoi polloi, Google, the IP bottom-feeders, etc.
In other words, "encryption to specific recipients" is already provided for in existing web standards and infrastructure. Browsers and servers will handle it automatically; in fact, many TLS stacks will handle it automatically for all the applications that use them.
Biting the hand that feeds IT
