Warn me when a certificate for a website I visited earlier changed.

Warn me when a certificate for a website I visited earlier changed.

Good day,

there are obviously scenarios where an attacker can provide a perfectly valid certificate for a given website, either by means of abusing a CA I trusted or by forcing that CA to sign his certificate and therefor the only mean to detect this attacker is by saving certificates formerly presented by this website and warning the user if these certificates changed.

Obviously, this will produce a false positive when the certificate is renewed once a year or so, but Opera could detect this “problem” and make the warning look nicer.

This feature would require Opera to save all previously seen certificates. Since these are not too many and certificates are not that big (typically around 2 KB) and there aren't too many websites you trust (maybe 1000? maybe 10'000? Surely not more than 100'000) the disk space required for this is not too big (between 2 and 100 MB, probably). Since this might be a problem for some users, there should also be a possibilty to turn off this feature.

The feature request you're currently reading is based on an idea by Felix von Leitner (Website) which also made it into the Mozilla Bugtracker a while ago.

Thank you very much for your attention,

x2017