Question

A symmetric cipher system has an IC of 0.041. What is the length of the key ‘m’?

(a) 1

(b) 3

(c) 2

(d) 5

The question was posed to me during an interview.

Question is taken from Substitution and Transposition Techniques in division Classical Encryption Techniques of Cryptograph & Network Security

Answer 1

Correct choice is (d) 5

For explanation I would say: Using the formula for calculating ‘m’ we get m=5, where

m≈0.027n/(I_c (n-1)-0.038n+0.065).