Re: stupid question
Fortunately (though not for ransomware cases), encryption algorithms are not usually vulnerable to what you describe as a "known plaintext" attack.
As an example for why this would be really bad for any serious use, think about encrypting a filesystem. If it's a Windows system, you can probably take a guess that it's NTFS, and try to break the algorithm based on likely locations for header structures and the like, or common document formats (docx, jpg, zip) or known executable images (ntoskrnl.exe, kernel32.dll might be good things to go hunting for.)
It's only particularly broken algorithms where known plaintext attacks work, and even then it usually only gives you a few bits more information that you don't have to crack (known plaintext was one of the attacks used against Enigma.)
Biting the hand that feeds IT
