Yeah, from 2008 R2 and up you need to install .Net Framework 3.5 as a Feature.
It gets enabled by certain Roles as dependency.
.Net Framework 3.5 is a funny thing, it's not really 3.5.
3.5 is a collection of 2.0 and 3.0, 3.5 itself doesn't exist as a framework.
.Net 4.0 is a separate framework, different sandbox altogether.
Apparently they didn't include the cryptography in 4.