Consider a variant of DES algorithm in which the S-box S1 is changed as follows:

For every six bit input a, the following property holds: Sl(a) = S1(a 001100) e 1111. All other S-boxes and operations remain the same. Design an algorithm to break four rounds of this variant. In order to get any credit, your algorithm must make use of the changed behavior of S1. For every six bit input a, the following property holds: Sl(a) = S1(a 001100) e 1111. All other S-boxes and operations remain the same. Design an algorithm to break four rounds of this variant. In order to get any credit, your algorithm must make use of the changed behavior of S1