The GPLv2 is not perfectly happy with DRM. It is very much possible to read the GPLv2 as requiring *all* material needed to install an executable, which would include keys:
“For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable.”
The GPLv2 was very much intended to allow end-users to be able to *install* modified works. The incident which motivated RMS to start this whole free software thing and come up with the GPL was a printer whose software he wanted to fix but couldn't. The freedom to modify software on hardware you own is what the GPL was intended to provide.
The GPLv2 is *not* "happy" with DRM. At best, this is an untested grey area simply because the GPLv2 predates the notion of DRM and so could not use the language we use today. However, it clearly intended to cover installation. The GPLv3 unambiguously fixes this wording issue. That does not mean the GPLv2 allows it though.