[NoKnowledge]

Yes, otherwise how would you know you are indeed communicating with that party?

Otherwise the standard Person-in-the-Middle attack would apply: Eve (claiming to be Bob) first runs a full protocol session (quantum + classical communication) with Alice, resulting in a shared key X. Then she does the same to Bob, resulting in a key Y. When Alice wants to encrypt a message to Bob, she encrypts with X. Eve can decrypt (and optionally re-encrypt with Y and forward the message to Bob).

[mikeiz404]

So the part I’m getting hung up on is if Eve attempts to MitM the quantum key exchange wouldn’t the probability of winning drop below the acceptable threshold since Eve does not posses the entangled particles? If that’s the case then wouldn’t Alice invalidate the exchange and same for Bob?