Encrypting large files using a public key
I need to encrypt a 100KB file using a public key. I've been reading some posts claiming that it is not practical to directly encrypt large files using a public key, and that the preferred method is to encrypt the file using a symmetric key and then encrypt this symmetric key using the public key. It seems that a naive solution would be to break the large file to pieces and encrypt each one of them using the same public key. My question is whether and why this solution is wrong?
Answer
The hybrid approach you mention (generate a random symmetric key, use this to encrypt the data, and encrypt only the key asymmetrically) has a massive performance advantage.
You could "break the large file to pieces and encrypt each one of them using the same public key" as well, there is nothing wrong with that, but it is much slower.