On corefx repo, we started using an Open key to fully sign some of our libraries. This key contains both public and private keys, and can be located here. This worked fine in Windows with the Full MSBuild and x-plat with Mono MSBuild, but it started failing x-plat once we moved to .Net Core MSBuild and the portable compilers. The exception we get is:

CSC : error CS7027: Error signing output with public key from file '.../corefx/Tools/Open.snk' -- Cannot marshal 'return value': Invalid managed [.../corefx/src/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj]

We would really like this issue to get addressed so that we are able to fully sign this libraries in non-Windows builds.