Cryptography

Question 1

What are the rules for one-time pads? <4>

Answer 1

• The key is at least as long as the plaintext
• The key is truly random
• Each key is used only once
• There should only be two copies of the key:
one for the sender and one for the receiver

Question 2

Define Asymmetric encryption

Answer 2

Public Key encryption

• Uses a different key for encryption and
decryption
• Depends on really hard maths problems..
• Need to generate key pairs
– Then choose one as private, the other as public

Question 3

Name 3 types of one-way functions

Answer 3

Modular Arithmetic
Prime Factorisation
Factorising Large Numbers