If I'm feeling paranoid about the CCDP (UK) - requiring ISPs to intercept communications across the internet - then what would be the most secure approach to a webmail system?
Obviously, there's some legal/political stuff (can I rely on the people running it, can I rely on the legal jurisdiction that it's located in, etc) but on a technical level, what would be a strong approach to running a webmail service that can't be cracked by an MITM attack run by my users' ISPs?
It strikes me that there are several things that will make a difference compared to a typical commercial service like Gmail:
- HTTPS, using TLS v.1.2 with well-selected cyphersuite choices (I'm not sure which cyphersuites would be right). Now that OpenSSL 1.0.1 is out, requiring TLS 1.2 is possible, though you'd lock out NSS-dependent browsers (Firefox and Chrome - which means Opera only on non-Windows OS; Safari/Win supports TLS 1.2 but not Safari/Mac).
- Deliver all content from a single domain name / IP address (no "static" domain, no ads, no Google Analytics, etc).
I'm not intending to actually implement such a service (I'm not in a suitable legal jurisdiction, for a start) but I'm sure there are other things that could be done.
Any suggestions, thoughts?