Question

In the DES algorithm the Round Input is 32 bits, which is expanded to 48 bits via ______________

(a) Scaling of the existing bits

(b) Duplication of the existing bits

(c) Addition of zeros

(d) Addition of ones

I got this question in exam.

The doubt is from Overview in division Cryptography Overview, TCP/IP and Communication Networks of Cryptograph & Network Security

Answer 1

The correct answer is (a) Scaling of the existing bits

For explanation I would say: The round key is 48 bits. The input is 32 bits. This input is first expanded to 48 bits (permutation plus an expansion), that involves duplication of 16 of the bits.