You were recently hired as a Cryptography Engineer at SecureIoT, a start$-$up company that

specialises in building solutions to secure IoT devices. You are asked to secure the wireless

communication between two devices which already share a private key. The deployed solution

needs to ensure that messages between the devices remain confidential and that the devices

can verify that the messages they receive are from the other device sharing the private key with

it$.$ The devices are deployed in an uncontrolled environment and hence the communications

between them may be observed, blocked, or modified by third parties.