Encryption

Question 1

What is encryption

Answer 1

A way of making sure data cannot be understood if you don’t possess the means to decrypt it

Question 2

Lowest and highest level of security

Answer 2

Lowest - Caesar
Highest - vernam

Question 3

How does encryption happen

Answer 3

Plaintext of a message sent is encrypted using a cipher algorithm and key into equivalent ciphertext
When received, the ciphertext is decrypted back to plaintext using the same or different key

Question 4

Caesar cipher

Answer 4

The Caesar cipher is most basic type of encryption and the most insecure
Letters of the alphabet are shifted by a consistent amount

Question 5

Brute force attack

Answer 5

A brute force attack attempts to apply every possible key to decrypt ciphertext until one works

Question 6

Vernam cipher

Answer 6

The encryption key, also known as the one-time pad, is the only cipher proven to be unbreakable
The key must be:
- a truly random sequence greater or equal in length than the plaintext and only ever used once
- Shared with the recipient by hand, independently of the message and destroyed immediately after use

Question 7

Decoding

Answer 7

Encryption and decryption of the message is performed bit by bit using an exclusive or (XOR) operation with the shared key

Question 8

The one-time pad

Answer 8

The one-time pad must be truly random, generated from a physical and unpredictable phenomenon

Question 9

Algorithmic security

Answer 9

Ciphers are based on computational security
- The keys are determined using a computer algorithm
- A key derived from an algorithm, can also be unpicked
- Given enough ciphertext, computer power and time, any key (except the one-time pad) can be determined and the message cracked