The big issue now is that there is a 9.8 scored vulnerability in DotNetZip (in the latest 1.16.0) and DotNetZip.Semverd itself is not longer maintained and thus archived by the dev.

As someone stated in the comments System.IO.Compression does not support encryption. And the only other "big" OSS library SharpZipLib seems to be unmaintained as well. So I think we have a serious problem now...

Does anyone know suitable alternatives? 7zip could be a candidate but using command line tool is not really convenient.