San Francisco-based security firm Qualys is throwing its support behind an experimental project designed to improve the security and privacy of website authentication by reducing reliance on certificate authorities that issue secure sockets layer credentials.
The Convergence project was devised by Moxie Marlinspike, a security researcher who has exposed repeated flaws in the SSL system that serves as the internet's foundation of trust. At the Qualys Security Conference in San Francisco on Thursday, the company said it was financing and running two new notary servers that Convergence users query to make sure the SSL certificate being offered by a given site is legitimate.
Most of the weaknesses Marlinspike has documented stem from the unwieldy number of organizations – about 650 by his count – authorized to cryptographically sign the certificates that PayPal, Gmail, and millions of other services use to prove their https-appended websites are authentic rather than easily forged counterfeits. With so many digital stamps, there are too many single points of trust. All it takes to subvert the system is for one of them to suffer a security breach like the one that hit Netherlands-based DigiNotar.
In stark contrast to the public key infrastructure at the heart of the SSL system, Convergence relies on a loose confederation of notaries that independently vouch for the authenticity of a given SSL certificate. Thursday's announcement by Qualys that it will run two of the servers is an important endorsement of the alternative project.
“Qualys running the notaries is a huge help and a step in the right direction,” Marlinspike said.
The move comes three weeks after Google developer Adam Langley said his team had no plans to fortify their Chrome browser with the crowd-sourcing technology. He cited a variety of practical considerations, including the technical strain Convergence would put on notaries, and the risk of Chrome breaking if they failed to keep up with the demand.
Qualys Director of Engineering Ivan Ristic said Langley's concerns were “perfectly valid,” but added that alternative approaches could easily break the potential bottlenecks the Google researcher envisioned. One possibility, he said, is to set up thousands of notaries that operate in a peer-to-peer fashion to balance the load.
“The challenge with Convergence is to get it into a state where you can use it without knowing it,” he said. “We need to figure out the mechanisms so it just works.”
A peer-to-peer design that distributes the load among huge numbers of notaries wasn't the precise blueprint Marlinspike envisioned when he proposed Convergence in April. One of the key benefits of the system was a “trust agility” that allows users to query specific notaries they trust.
Another advantage of Convergence is its use of two separate notaries that, for privacy reasons, are intentionally kept in the dark when vouching for a certificate. One notary gets to see the IP address of the Convergence user but not the SSL certificate she wants validated. The other one sees the certificate but not the IP address.
The design is intended to remedy a fundamental weakness of the current system, which allows certificate authorities to track huge numbers of individual requests for SSL-protected websites. This shortcoming was brought home in the aftermath of the DigiNotar breach, when it was revealed the CA logged the time and IP address for more than 300,000 IP addresses exposed to a counterfeit Google.com certificate.
So far, Convergence is made up of about 50 notaries. It works only on the Firefox browser running an add-on. Ristic has more about the new notaries here. ®