Say I have four files. Two are completely unencrypted, while the other two are the exact same files other than that they have been encrypted with (apparently) the same public key (via a ransomware virus). Is it possible to deduce the key from these files, so I can apply it to other files also encrypted with the same key?
Sorry, after searching through the questions related to my tags, I see the simple answer is no, because although the public key is easily discovered, it's probably a private key I'm looking for, which would be hosted elsewhere.
But to modify the question:
- Does the length of the public key imply the length of the private key, or can they be unrelated?
- Also, wouldn't more plaintext information provide a brute-force program a starting point to speed the process?
I don't understand why, given that all the files would be decrypted using the same key, we can't deduce said key by comparing encrypted files to unencrypted ones.