https is likely the most widely used cryptographic protocol. It's based on X.509 certificates. There's a living debate how useful this concept is at all, mainly through the interesting findings of the EFF SSL Observatory. But that won't be my point today.
Pretty much all webpage certificates use RSA and sadly, the vast majority still use insecure hash algorithms. But it is rarely known that the X.509 standards support a whole bunch of other public key algorithms.
I'd be very interested to get some feedback. If you happen to have some interesting OS/Browser combination, please import the root certificate and send me a screenshot where I can see how many green ticks there are (post a link to the screenshot in the commends or send it via email).
At the moment, I'm especially looking for people to test:
Internet Explorer 9 on Windows 7
Safari on latest MacOS X
Internal browser on iPhone (I don't know if it's possible to install a new certificate authority there)