Symmetric Encryption Introduction

Question 1

What is the most famous and earliest form of Symmetric Encryption?

Answer 1

Caesars Cipher. This was a mono-alphabetic substitution cipher in which all characters in the message substituted by another character in the alphabet, based on a certain jump. For example, is the jump was 3 forward, then A would substituted for D. The symmetric key in this encryption is the jump.

Question 2

What are the 5 components needed to carry out Symmetric Encryption?

Answer 2

Plaintext message, Encryption algorithm, cipher text, decryption algorithm, key.

Question 3

What is the relationship between the encryption and decryption algorithm?

Answer 3

They are the inverse of one another.

Question 4

What are the 2 main requirements when using symmetric encryption? Why are they needed?

Answer 4

1. Strong encryption algorithm - Such that even if given multiple cipher texts, attackers can’t compute the key using the cipher texts and the algorithm.
2. Shared secret - The symmetric keys must remain a confidential secret between the parties involved.

Question 5

What are the 2 main types of attacks used on Symmetric Encryption?

Answer 5

1. Cryptanalysis - This is the analysis of the algorithm in order to deduce the plain text or encryption key used on a cipher text. If the key is deduced, all encrypted data with that key is compromised.
2. Brute force - Given a cipher text, keys are continuously generated and ran through the decryption algorithm in hope that one of them decrypts the message.