1suppose alice, bob, and carol want to use secret key technology to authenticate each other. if they all used the same secret key k, then bob could impersonate carol to alice (actually any of the three can impersonate the other to the third). suppose instead that each had their own secret key, so alice uses ka, bob uses kb and carol uses kc. this means that each one to prove his or her identity responds to a challenge with a function of his or her secret key and the challenge. is this more secure than having them all use the same secret key k?

Agas contained within a piston-cylinder assembly e end nation about same energy states, 1 and 2, where pi 10 bar, v undergoes two processes, a and b, between the sam 0.1 m3, ui-400 kj and p2 1 bar, v2 1.0 m2, u2 200 kj: process a: process from 1 to 2 during which the pressure- volume relation is pv constant process b: constant-volume process from state 1 to a pressure of 2 bar, followed by a linear pressure-volume process to +20 0 state 2 kinetic and potential energy effects can be ignored. for each of the processes a and b, (a) sketch the process on p-v coordinates, (b) evaluate the work, in kj, and (c) evaluate process the heat transfer, in kj