I want to backup folders to encrypted split files of a certain size. And periodically I'd do incremental or differential updates to that, with new split files with a different name (date). Ideally I'd like a common format (zip, 7z, rar...) and/or something open source that I can use in the long run, but I'm not ruling out a proprietary solution. The closest I've found so far is 7-zip. It does almost everything I want, the only problem is that it can't make differential backups from split archives. So I need to have a single 7z file as a base. Another one that comes close is "BackUp Maker", it produces .zip files. But the zip headers (file names) aren't encrypted. And also when restoring the differential backups it doesn't remove the deleted files. I read somewhere that WinRAR can make differentials from split archives, but I couldn't find a way to do it. What would I enter in the command line to set the *part* files as the base?