4b Encryption

Question 1

What is meant by perfectly secure?

Answer 1

Code will never be broken no matter how much time someone has

Question 2

What 3 conditions must be met for a cipher to be perfectly secure?

Answer 2

1. Key must only be used once
2. Key must be truly random
3. The key must be only be know to the user

Question 3

Why is the Caesar cipher?

Answer 3

A cipher where each letter is substituted/shifted to another letter
E.g. with a shift of 1 a would be replaced by b and so on

Question 4

What is the vernam cipher?

Answer 4

A cipher that uses a one time pad that generates a long sequence of random letters that are combined with the plain text to encrypt it.
In theory it is perfectly secure.

Question 5

How do you encipher a message?

Answer 5

Take the ascii of the letter in the message and xor it with the ciphers letter.