Things that use OpenPGP or libOTR. At the level of an organization where you can run your own CA, X509 might be easier (it's integrated into outlook IIRC).
I don't know what the accessible frontends are and no doubt there's work to be done there, but the basic primitives are a solved problem, and I'm pretty sure a better frontend on top of either would be very welcome.
Comments
Things that use OpenPGP or libOTR. At the level of an organization where you can run your own CA, X509 might be easier (it's integrated into outlook IIRC).
I don't know what the accessible frontends are and no doubt there's work to be done there, but the basic primitives are a solved problem, and I'm pretty sure a better frontend on top of either would be very welcome.