Mozilla has proposed a new method for signing into websites that avoids both site-specific passwords and existing cross-site sign-in services from corporate behemoths such as Google and Facebook.

Known as BrowserID, Mozilla's prototype is built atop a new "Verified Email Protocol", which uses public-key cryptography to prove that a particular user owns a particular email address. In essence, BrowserID lets you log into a website simply by clicking on a button and choosing an email address you wish to sign in with. Behind the scenes, the website, your browser, and a separate verification service use crypto keys to verify your identity.

"For a Web developer, creating a new application always involves an annoying hurdle: how do users sign in? An email address with a confirmation step is the classic method, but it demands a user’s time and requires the user to take an extra step and remember another password. Outsourcing login and identity management to large providers like Facebook, Twitter, or Google is an option, but these products also come with lock-in, reliability issues, and data privacy concerns," Mozilla says in a blog post, referring to services based on OpenID and similar protocols.

"With BrowserID, there is a better way to sign in. ... A user can prove their ownership of an email address with fewer confirmation messages and without site-specific passwords."

To set up BrowserID, the user supplies an email address and a password. This is then sent to the verification service, which returns an email to your inbox so you can verify that you indeed own that email address. (The process is similar to the email-based password-reset services so many websites use today). The service then creates a cryptographic key pair, keeping the public key and storing the private key with your browser.

When you later visit a website that's set up for BrowserID, you simply click on a "sign-in" button and select your registered email address (you can register more than one). The site then retrieves the keys to verify your identity.

The ultimate idea, however, is to convince mail providers to adopt the system, so that a separate verification service isn't needed. "Anyone with an email address can sign in with BrowserID, and email providers can implement BrowserID support to make the system even easier for their users," Mozilla says. But even with the verification service, the setup is quite simple.

The service does collect a list of sites you share your email with, and if mail providers enter ithe mix, they will have access to such data as well. But Mozilla argues that unlike other cross-site sign-in services, BrowserID doesn't leak data back to any other servers.

The open source outfit also says the system is superior to OpenID and other identity token–based protocols because it puts so little between the user and the site they're visiting. "A number of web-scale identity proposals start by creating a new identity token – for example a user ID or personal URL – and go on to describe how to use that token to authenticate the user," Mozilla says on a wiki describing the Verified Email Protocol. "What we've learned from several years of experience with OpenID (and related protocols) is that this isn't quite good enough: establishing an identity token, in isolation from the rest of the web, doesn't actually help a site engage with its users."

Developers can go here for the JavaScript needed to add BrowserID to their sites, and browsers uses can sign into a test site here. The prototype is built with HTML and JavaScript, so it runs on all newer browsers, including mobile browsers. ®