This is a cryptography question from the book Introduction to Modern Cryptography by Katz and Lindell. If needed, please refer to the textbook's online pdf (http://www.cs.sfu.ca/CourseCentral/404/abulatov/exercises/sol4-15.pdf (Exercise 9.2) to answer the question.

9.2 Consider the following key exchange protocol that is based on the one- time pad and perfect secrecy: (a) Alice chooses a random key k and a random string r both of length n, and sends s k r to Bob. (b) Bob chooses a random string t of length n and sends u 3s t to Alice (c) Alice computes w u T and sends w to Bob. (d) Alice outputs k and Bob computes w 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 bre