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Question 21 - 212-81 discussion

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A technique used to increase the security of block ciphers. It consists of steps that combine the data with portions of the key (most commonly using a simple XOR) before the first round and after the last round of encryption.

A.
Whitening
Answers
A.
Whitening
B.
Key Exchange
Answers
B.
Key Exchange
C.
Key Schedule
Answers
C.
Key Schedule
D.
Key Clustering
Answers
D.
Key Clustering
Suggested answer: A

Explanation:

Whitening

https://en.wikipedia.org/wiki/Key_whitening

In cryptography, key whitening is a technique intended to increase the security of an iterated block cipher. It consists of steps that combine the data with portions of the key.

The most common form of key whitening is xor-encrypt-xor -- using a simple XOR before the first round and after the last round of encryption.

The first block cipher to use a form of key whitening is DES-X, which simply uses two extra 64-bit keys for whitening, beyond the normal 56-bit key of DES. This is intended to increase the complexity of a brute force attack, increasing the effective size of the key without major changes in the algorithm. DES-X's inventor, Ron Rivest, named the technique whitening.

Incorrect answers:

Key Clustering - different encryption keys generated the same ciphertext from the same plaintext message.

Key Schedule - an algorithm for the key that calculates the subkeys for each round that the encryption goes through.

Key Exchange - a method in cryptography by which cryptographic keys are exchanged between two parties, allowing use of a cryptographic algorithm.

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asked 18/09/2024
Alexey Chernikov
32 questions
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