If your company would like to use VPN to create the secure communication with all customers. Your company applies AES$-128$bits $($Advanced Encryption Standard$)$ to provide VPN services for the communication between you and the company. There must be a safe symmetric key exchange for AES in VPN before a secured communication channel can be created. There is an algorithm which allows two parties to share a common secret withoug a third party involved. This common secret can help AES's symmetric key exchange process.

$1)$ Which algorithm is this?

$2)$ Undertake a cryptanalysis on if a middle person can figure out what this shared key is$.$