Question

The substitution cipher uses a key domain of 20 keys and the alphabet of 20 characters. Assume the redundancy is 0.5. What is the unicity distance?

(a) 1
(b) 10
(c) 20
(d) 2​

Answer 1

Answer:

CORRECT ANSWER IS (d)

Explanation:

U= H(k)/D

D= Redundancy  

D=R-r

R=8 or approximate 7, r=1.5,

H(k)= 20

so,

U= 20/5.5

we get unicity distance (U) approximate = 2