Block Cipher Modes

Question 1

ECB (electronic code book)

Answer 1

Each plaintext block encrypts with same key

Question 2

CBC (Cipher Block Chain)

Answer 2

First Block uses IV XOR’d with the key
All other blocks are XOR’d with previous block

Question 3

CTR (counter) stream

Answer 3

Acts like a stream cipher
The block is a blank counter

Key is XOR’d with plaintext to create ciphertext.
Next block increases the counter by 1

Question 4

GCM (Galois counter mode)

Answer 4

Encryption and authentication Minimum latency
Used in Wi-Fi and TLS
(Used by WPA3)

Question 5

PCBC (propagating CBC)

Answer 5

Used as a federal standard

Question 6

OFB (output feedback) stream

Answer 6

Used for streaming.
(Often used for Wi-Fi and secure websites)
AES block cipher similar to CFB mode.

Question 7

CFB (cipher feedback)

Answer 7

AES block cipher similar to CBC in that it uses the cipher of the previous block.
Meant for streaming and doesn’t require padding.