Ran into a speedbump while configuring a new Office Online Server for a SharePoint 2016 farm and wanted to share the solution I found from a colleague: https://blogs.technet.microsoft.com/dodeitte/2012/07/20/issue-when-installing-windows-identity-foundation-on-windows-server-2012/
If you are running Windows Server 2012 R2, you will find that this is a feature you enable, not an download from a KB article.
When you kick off the install for Office Online Server, you'll get a failure that Windows Identity is not installed and a handy reference to the KB Article (https://www.microsoft.com/en-us/download/details.aspx?id=17331) But there's no version there for Server 2012. And if you try t0 install one of the versions there, you'll get an unhelpful message about the signing of the package.
So hopefully I'll save you some head-scratching and confusion: Enable the feature, and you'll be all set.
And if you're wondering why this has changed, if you think about the differences in Identity products -- like FIM/MIM/ADFS -- you may remember from your training that Server 2012 has much of this "built-in", not as an additional download.