Cryptograhpy2

Question 1

What is confusion in cryptography?

Answer 1

Confusion adds an unknown key value to confuse an

attacker about the true value of a plaintext symbol

Question 2

What is diffusion in cryptography?

Answer 2

Diffusion spreads the plaintext information through the

ciphertext?

Question 3

What are substitution-permutation

networks?

Answer 3

Early (modern) block ciphers used simple networks
combining substitution and permutation circuits
These networks are called substitution-permutation
networks (or SP networks)

Question 4

what is the basic concept of a substitution box (sbox) operating on 16-bit blocks

Answer 4

A substitution box (S-box) is basically a look-up table

containing some permutation of the numbers 0 to 15

Question 5

How does a SP network work?

Answer 5

The mapping used for the S-boxes needs to be one-to-one
(so decryption is possible)
The output of S-boxes is shuffled with a permutation
network before being fed into the next layer of S-boxes
Each layer is also called a round