I had the privilege to address the annual Chaos Communication Congress (36C3) in Leipzig last week about the state and remaining issues in private communications.
The TL;DR for me is that many of the trade-offs are balancing the stability of user experience with privacy mechanisms – and finding more ergonomic user experience interactions will be as important as new systems schemes are to improving the ecosystem.
I am particularly excited by the number of ongoing effort reducing trust in central servers. Many of the mechanistic trade-offs we face are due to the topology of our systems. With systems designed for fully anonymous interaction, like mixnets, PIR, and oblivious messaging, we can model and mitigate threats from much more realistic adversaries than we do with popular channels today. (For instance, consider an office which has received a whistle blowing message. If the receiving investigation wants to identify the source, they likely control both the local network, and have the ability to send messages to the account that initiated the conversation. Our current designs will find it quite difficult to protect a user from this scenario)