difference is accurately the same as the language suggest.
“Shared key” means that the same
key is used by several party. It doesn’t tell you how the key was distributed
“pre-shared key” means the key has been shared
before the current operational context.
See these examples:-
you perform a Diffie-Hellman key exchange in an SSL connection, you actually
generate a new key that is shared by both client and server without any of them
having a previous knowledge of that key. That key is shared but not pre-shared.
you protect a ZIP file with a password, this password becomes the shared key
and it must be shared between all parties. That key is both shared (everyone
uses the same) and pre-shared (its distribution isn’t covered by the ZIP
protocol and must be performed through a different secure channel before usage)
are only two examples, there are many more. I hope this is helpful for you.
Thanks & Regards