During March 2019 updates, Microsoft will be improving security for its Windows Update (Patch Tuesday) process by adding SHA-2 encryption as shared below  

https://www.pcmag.com/news/366610/still-using-windows-7-microsofts-next-update-is-critical

If you want to continue receiving Windows updates, then the next Windows 7 and Windows Server 2008 update is critical as it adds support for SHA-2 encryption. Without it, future updates can’t be downloaded.

As MSPoweruser reports, Microsoft needs to ensure that the operating system updates end users receive haven’t been tampered with. It does this using SHA-1 and SHA-2 hash algorithms to authenticate the updates. The problem is, the SHA-1 algorithm has a weakness and can no longer be relied upon.

As Windows 7 SP1, Windows 2008 SP1, and SP2 all rely on SHA-1 encryption, they need updating with support for SHA-2 as future Windows updates will require it. So next month Microsoft is rolling out an update to add support for SHA-2 encryption for its oldest supported operating systems. If you’re a Windows 7 user and don’t install this critical update, wave goodbye to any future Windows patches