Maybe it's late and my brain is starting to fade out, but Mozilla's documentation for the keygen tag is giving me a headache:

"The KEYGEN tag facilitates the generation of key material and submission of the public key as part of an HTML form. This mechanism is designed for use in web-based certificate management systems. It displays a menu of key-size choices from which the user must choose one. Then, when the submit button is clicked, a key pair of the selected size is generated. The private key is encrypted and stored in the local key database. The public key and challenge string are DER encoded as PublicKeyAndChallenge and then digitally signed with the private key to produce a SignedPublicKeyAndChallenge. The SignedPublicKeyAndChallenge is base64 encoded, and the ASCII data is finally submitted to the server as the value of a name-value pair, where the name is specified by the NAME attribute of the KEYGEN tag."

Check out what it does:

It works in Firefox, anyway...

Has anyone actually used this? Can you provide an example? Drop by our forums if you can shed some light on how this might be appropriate on a page.