Computer Networks Suppose Alice and Bob want to play poker o

(Computer Networks) Suppose Alice and Bob want to play poker over the network.

Suppose Alice and Bob want to play poker over the network. To deal the cards they need a mechanism for fairly choosing a random number x between them; each party loses the game if the other party can unfairly influence the choice of x. Hence they will do the following. (a) Alice and Bob generate random numbers x_1 and x_2, respectively. (b) Alice first sends x_1 to Bob. (c) Bob then sends x_2 to Alice. (d) Both Alice and Bob calculate x = x_1 x_2, and use x as the agreed random number. In the last step, we use the assumption that, if either of two bit strings x_l and x_2 are random, then the exclusive x = x_1 x_2 is random. But there is a problem in this procedure. In Step (c), Bob may become dishonest; he may first look at x_1 received from Alice, and try to generate x\'_2 based on x_1 in his favor, and send that x\'_2 to Alice instead of x_2. So we need a mechanism to prevent such situation. Describe such a mechanism.

Solution

Here we need to implement an mechanism such that while exchanging the random numbers between two users must be reliable. Follow the below steps to achieve the reliability of random number exchange

example:

x1 =1001

x2=1010

then x3 =1111

compute x4= x2 XOR x3 = 0101

Now send x1 to Bob

Recieve some x2\' =1011 from Bob this is to be verified

such x5= x2\' XOR x4

= 1011 XOR 0101

=1110

since x3 Not Equal to x5 then the value x2\' send from the Bob is incorrect

By this mechanism we can ensure that the Bob will send the correct x2 value to the Alice