Section 8.69 Symmetric vs Asymmetric

Question 1

Symmetric Encryption
(aka Private Key Encryption)

Answer 1

■ Encryption algorithm in which both the sender and the reciever must know the same shared secrect using a Private Key

More people = more sharing of the same Private Key

e.g Key to a house - shared key

■ Challenges with key distribution in large-scale usage: More people means more sharing of the keys

Question 2

Asymmetric Encryption
(aka Public Key Cryptography)

Answer 2

Encryption alogrithm where different keys are used to encrpypt and decrypt the data

Public key for encryption
Private key for decryption

■ Slower compared to symmetric encryption but solves key distribution challenges

Question 3

Hybrid Approach

Answer 3

■ Combines both symmetric and asymmetric encryption for optimal benefits

Asymmetric encryption: To encrypt and share a secret key

Symmetric encryption: For bulk data transfer, leveraging the shared secret key

• Sender generates a one time use Session Key
• One time Session Key is encrypted using the recievers public key protecting the data
• Recievers Private key decrypts the one time Session Key
• Both users now have the same key and switch to faster Symmetric AES

Hybrid offers security and efficiency.
CONVENTIONAL KEY

Question 4

Types of Ciphers

Stream Cipher

Answer 4

Utilises a keystream generator to encypt data bit by bit or or byte-by-byte using a mathematical ‘exclusive or’ (XOR) function to create the ciphertext

■ Suitable for real-time communication data streams like audio and video

■ Often used in symmetric algorithms so use the same key for encyption and decryption

PLAIN TEXT to CIPHER TEXT - use process such as stream cipher or block cipher

Question 5

Types of Ciphers

Block Cipher

Answer 5

Breaks the input into fixed-length blocks of data and peforms the encryption on each block rather than bit by bit

● Usually 64, 128, or 256 bits at a time

■ Padding added to smaller data blocks to fit the fixed block size (less than 64 bits)

■ Advantages include ease of implementation and security HOWEVER Stream cipher is quicker
■ Can be implemented in software, whereas stream ciphers are often used in hardware solutions