Is the following authentication protocol insecure? I am a student taking cryptography this semester. I was just wondering why can't we use this simple protocol? 

Alice → Open Connection → Bob
Alice ← Cert$_b$ ← Bob
Alice → {K$_{AB}$}$_{Bob}$ → Bob

Assume bob is the server and we're only interested in one way authentication.
Is there anything wrong with it in terms of security and performance?
Bob needs proof that Alice is authentic: 
A-Open Connection-Cert partial random key->B Both keys combine to form an access key.

Standard one-way authentication protocol only requires submitting a correct password once, in order to gain access and control. By randomizing part of Alice's password, significantly reduces the likelihood of her password becoming victim of replay attacks and man-in-the-middle-attacks, just to name a few. [Random Assymetric] Bob's server has been preset for random variations of Alice's hash value


Is there anything wrong with it in terms of security and performance?


Technically speaking, there is nothing wrong with your suggested one-way authentication protocol. However, the security function of your protocol can be increased by preconfiguring Bob's server with random hash variations of Alice's password for added security. Best of luck with your protocol