Question

What type of algorithm does AES encryption use?

(a) Stream cipher

(b) Symmetric block cipher

(c) Asymmetric caesar cipher

(d) DES encryption

I have been asked this question in examination.

My question is from Cryptography topic in section Number Theory and Cryptography of Discrete Mathematics

Answer 1

The correct choice is (b) Symmetric block cipher

To elaborate: AES encryption uses symmetric block ciphers to encrypt the messages. It is at least 6 times faster than 3 DES. AES uses a substitution-permutation network and this network is a series of operations that either replaces input with output bits (substitution) or shuffles the bits (permutation). It uses 128-bit input plaintext and it operates on bytes rather than bits. Here, the input is represented as 16 bytes (because 128 bits = 16 bytes) and is arranged in a 4 x 4 matrix.