A team is designing a lightweight Feistel cipher for IoT devices. They plan to use a 64-bit block size and a round function that operates on 32-bit halves. Which statement about the round function is correct?

The round function must be the same in every round to simplify key scheduling.

The round function must include an S-box to provide security.

The round function can be any function, even a non-invertible one, because the Feistel structure ensures decryption.

The round function must be a bijection to allow decryption.

How are the 16 subkeys generated in DES?

By permuting the 56-bit key with PC-1, then repeatedly shifting halves and applying PC-2

By encrypting the key with itself using DES

By applying the S-boxes to the original key 16 times

By XORing the key with a constant for each round

What is the purpose of the ShiftRows transformation in AES?

To XOR the state with the round key

To substitute each byte with a value from the S-box

To diffuse the influence of a byte across multiple columns

To mix the bytes within each column using matrix multiplication

A security engineer is explaining DES's key schedule to a new hire. The new hire asks why the key is often described as 64 bits but the effective key length is 56 bits. What is the correct explanation?

The key is 64 bits, but the algorithm discards 8 bits during the initial permutation to speed up processing.

Eight of the 64 bits are used as parity bits and do not contribute to the key's entropy.

The key is 64 bits, but the S-boxes only accept 56 bits of key material.

The key is 64 bits, but only 56 bits are used because the remaining 8 bits are reserved for future expansion.

EC-CouncilCertified Encryption Specialist

Domain 2Objective 1

Feistel Networks, DES, 3DES, and AES ECES Practice Questions (Page 6)

Part of the Symmetric Cryptography and Hashing domain, which makes up ~17% of our current practice bank. EC-Council does not publish an official question count, but from its 120-minute exam (~50–80 total, ~9–14 in this domain), expect 3–5 from this objective — we provide 51 practice questions to prepare you well beyond it. (estimate)

51questions here

11free pages

12concepts

Questions 26–30

26application · medium
A team is designing a lightweight Feistel cipher for IoT devices. They plan to use a 64-bit block size and a round function that operates on 32-bit halves. Which statement about the round function is correct?
Select an answer first
27foundation · easy
How are the 16 subkeys generated in DES?
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28foundation · easy
What is the purpose of the ShiftRows transformation in AES?
Select an answer first
29application · easy
A security engineer is explaining DES's key schedule to a new hire. The new hire asks why the key is often described as 64 bits but the effective key length is 56 bits. What is the correct explanation?
Select an answer first
30foundation · easy
In a Feistel network, what is the typical operation applied to combine the output of the round function with one half of the data block?
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