Consider the following key-exchange protocol that is based on the one time pad and perfect secrecy

Consider the following key-exchange protocol that is based on the one time pad and perfect Secrecy Alice chooses a random key k and a random string r both of length n, and sends s = Circular plus r to Bob Bob chooses a random string t of length n and sends u = s Circular plus t to Alice. Alice computes w = u Circularplus r and sends w to Bob. Alice outputs k and Bob computes w Circularplus t. Show that Alice and Bob output the same key. Analyze the security of the scheme (i.e., either prove its security or show a concrete break)