Quiz 1

Question 1

What should a symmetric encryption scheme satisfy to be secure?

Answer 1

1. The relationship between the plaintext and the ciphertext should be complex.
2. It has a large key space.

Question 2

What is the “The Kasiski Examination”? What cypher is it relevant to?

Answer 2

A technique used to attack the Vignere cypher.

Analyzes the distances between repeating sequences of characters in the ciphertext to determine the likely length of the key. These distances often have common factors which are candidates for the length of the key.

For example, 5, 10 and 2 would all be valid guesses for a distance of 10 as they are all factors. 3 on the other hand, would not.