In this question h$$ is a cryptographic hash function that has the

following properties:

$1.$ Given h$($x$)$ and y where x and y are integers, it is possible to quickly compute h$($x$$y$)$

$($where $$ denotes multiplication$).$

$2.$ Given h$($x$)$ and h$($y$)$ where x and y are integers, it is impractical to compute h$($x $$ y$).$

Assume A and B have been participating in an ongoing non$-$confidential online exchange

$($hence not using any form of encryption$).$ Suddenly A tells B that the rest of their online

interaction is confidential and should be encrypted using a session key that they must

somehow agree on$.$ They do not have a shared secret, and neither of them has a public

key, therefore the information they exchange in any protocol they use for agreeing on a

session key k$,$ will be visible to adversaries like Eve or Mallory. This question is about the

suitability of the following protocol for A and B to agree on a session key k and using it to

communicate confidentially.

$1.$ A

h$($rA$)$

$->$ B

where rA is a large integer randomly selected by A

$2.$ A

h$($rB$)$ B

where rB is a large integer randomly selected by B