Module 4

Question 1

What is substitution cipher? give examples ?

Answer 1

• only change the content of the PT not the position

- Ceaser, vigenere, playfair.

Question 2

What is transposition cipher? give examples ?

Answer 2

• only change the position of the PT not the content

- rail fence, matrix transposition

Question 3

what is mono-alphabetic substitution cipher ? give example ?

Answer 3

fixed substitution for each letter

teaser cipher

Question 4

what is poly-alphabetic substitution cipher ? give example ?

Answer 4

variable substitution, substitution can be different depending on the position of the PT

vigenere cipher, playfair cipher

Question 5

limitations of traditional key crypto systems ?

Answer 5

• frequency analysis
• educated guess
• reverse engineering use known plaintext attack, chosen plaintext and cipher text attacks.