4.5.6.8 Encryption

Question 1

What is encryption?

Answer 1

Using an algorithm to convert a message into an unreadable form or ciphertext so only the intended receiver can use their key to decrypt the message.

Question 2

How is the two-key system used to encrypt and decrypt?

Answer 2

The data is encrypted with the receiver’s public key, and the receiver uses their private key to decrypt the data

Question 3

Why is caesar cipher easy to crack?

Answer 3

Because it uses symmetric encryption, the same key is used to encrypt and decrypt

Question 4

How does a caesar cipher work?

Answer 4

Replace each plaintext letter with a different one a fixed number of places down the alphabet, using a key.

Question 5

How does the vernam cipher / one time pad work?

Answer 5

The key is a set of letters at least as long as the plaintext (so it may be repeated).
In order to cipher a text, take the first letter of the message and the first letter of the key, add their value and find the corresponding letter.
The key must be used once only. The key is known as a one-time pad

Question 6

Explain why Vernam cipher is considered as a

cypher with perfect security

Answer 6

Vernam cipher is the only one to have been
mathematically proved to be completely secure. In theory, every cryptographic algorithm except for Vernam cipher can be broken, given enough ciphertext and time.