HonzaZ
26
It is the same with real signature, really. If you personally sign 100 different papers, someone (for example I) can still prove the signature is the same.
And it is the same with files - one signature can sign unlimited number of files, and still the signature is the same.
More info for example here: https://en.wikipedia.org/wiki/Digital_signature but I am sure there are many more explanations on the Internet 