The Mozilla Foundation has stepped up its efforts to improve browser security with the launch of Firefox 32, adding public key pinning to try and protect users from man-in-the-middle and other attacks.

The change is among a bunch of enhancements offered in the new version, now available for Windows, Mac, Linux and Android users.

Public key pinning is designed to relieve users of some of the burden of keeping track of certificates, since the trusted sites – at the moment addons.mozilla.org and Twitter, with Google to come soon – can instruct the user agent to remember the host's cryptographic identity for a specified amount of time (the IETF spec is here).

Pinning, Mozilla says, improves the security of implementations such as TLS. It “allows site operators to specify which CAs issue valid certificates for them, rather than accepting any one of the hundreds of built-in root certificates that ship with Firefox.

“If any certificate in the verified certificate chain corresponds to one of the known good (pinned) certificates, Firefox displays the lock icon as normal. When the root cert for a pinned site does not match one of the known good CAs, Firefox will reject the connection with a pinning error.”

In addition, a bunch of 1024-bit trust certificates have been removed from the list that Firefox trusts.

Other key changes in the new version include a revamped cache, which first made it into the code base in May, designed to provide better crash recovery and improved performance; and easy language switching in Android, regardless of which language the user originally downloaded the browser in.

The full changelog is here.

There's also a bunch of security advisories addressed in the new version. ®