I’ve been trying to get my head around this and I’ve watched a few videos but they don’t seem to specifically answer my question.
According to what I’ve found online, messages encrypted with a public key can only be decrypted with a private key. But in practice, how is that possible?
Surely a public key contains a set of instructions, and anyone could just run those instructions in reverse to decrypt a message? If everything you need to encrypt a message is stored within a public key, then how is it a one-way process?
It’s likely that I’m misunderstanding a core element of this!
Not exactly. But that is not the point.
No, you can’t, and that’s exactly the great thing about the invention of public key crypto (or asymmetric encryption in general).
You can encrypt something with a private key, and then you need the public key to decrypt it. That is used for a digital signature.
You can encrypt something with a public key, and then you need the private key to decrypt it. That is used for a private message to one person.