I predict this post will receive between 2-6 votes and never see the front page, but for what it's worth: this is the most important thing happening in Internet security this year.

One of the biggest problems we have in security right now is that nobody knows how many SSL CA's there are. The SSL PKI has failed. Browser vendors allowed top-level CAs to delegate, often for money, their signing authority to third-parties. Those third parties have in turn done predictably horrible things with that privilege. One of them sold a CA=YES certificate to a Fortune 500 company to help them monitor their employees (and also the whole Internet). Several others were hacked.

The problem with untrustworthy CAs is that the browser depends on CA trust to "break ties" between competing certificate assertions; is this Bank of America certificate BofA, or is it a European organized crime group? The only signal the browser has is which CA the signature on the cert rolls up to.

Google ameliorated that problem for its own properties using "certificate pinning". Pinning simply means that Google knows what their legit certificates are, and ships a browser, and sure as shit isn't going to let its browser trust some dinky delegated CA's certificate for GMail over the certificate it knows it owns. It sure would be nice if everyone could pin their certificates into browsers instead of just Google and the giant sites Google pins.

TACK allows that to happen. TACK is a small cryptosystem that accomplishes for certificate pins what HSTS (a widely supported browser security standard) does for defeating SSL stripping: it provides a way for browsers to see a legit SSL/TLS certificate and then remember that certificate going forward, so even if Iranian hackers (or the NSA) manage to cut a valid-looking CA-signed certificate for that site later on, it won't matter because your browser will only honor the cert it first saw. The technique, which is called "key continuity" and forms the entire security model for SSH, relies on the fact that the overwhelming majority of first-contact hits to sites will get their legitimate key; if you're an attacker with an evil certificate, your odds of intercepting a first-touch connection from a browser to BofA is very low.

You very much want TACK to get as much attention as it can. Trevor Perrin and Moxie Marlinspike are extraordinarily competent and well-regarded crypto protocol people and TACK is both simple and well- thought- out. TACK takes some of the control maintained by browser vendors back and returns it to site operators. This kind of decentralization is badly needed. Read the TACK draft, please.