Windows – How to generate MD5 hash value for multiple files in a folder using cmd

You could recursively generate all the hashes, concatenate the hashes into a single file, then generate a hash of that file.

Hash algorithms read the input and process it, no matter if there's data at all. This is a valid and wanted behaviour and is even used to verify if a certain implementation is correct. This leads to "null-hashes" for all major algorithms.

To sum it up: da39a3ee5e6b4b0d3255bfef95601890afd80709 is the sha1-hash for an empty file everywhere, the same is true with the null-hashes of other alrogrithms.