CS472

Assignment #5

Due Midnight, Thursday Nov. 19, 2009

Q1:

 

Assume each individual digit of a message M= 1020304  is encrypted with K=3.

What is the value of the resulting  cipher assume we are using:

 

A.    Mod 5 addition

B.    Mod 5 multiplication

C.    Mod 5 exponentiation

Q2:

A.     Verify that d=<65, 133> is the corresponding private key of   e=<5, 133>.

B.     Use the efficient exponentiation scheme described in RSA to encrypt a message M = 100.

 

NOTE:

To make sure that your answers are correct, encrypt the message M and make sure that you get back C.

Q3: 

Assume that A and B, and C are using Diffie-Hellman with  p=19 and g = 7.

Let  SA = 11 and SB = 13, and SC = 17. 

In order to avoid the man-in-the-middle attack, they deposit their public values PA , PB  and PC with a trusted authority (TA).

1.     Compute the public values PA , PB  and  PC 

2.     Compute the shared secret between each pair of these individuals based on the values deposited with the TA