3, Modern block ciphers combine substitution S and permutation P operations to improve security. Based on the security rule, the cipher should not use consecutive substitutions or consecutive permutations. In the following combinations, which one violates the above security rule? ?1?1?2?2B. ?1?1?2?2C. ?1?1?2?2 4, Which description about the DES cipher is NOT correct? The block size of DES is 64 bits.The DES cipher is based on the Feistel Cipher Structure.When the plaintext is encrypted using DES twice (Double DES) with two different keys, the key search space increases from 256 to 2112.Triple DES is more secure compared with original DES.

Answer : Choice (3) is the incorrect option Exp. 1: The DES encryption algorithm is a “block…

Answered: 3, Modern block ciphers combine…

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Question

3, Modern block ciphers combine substitution S and permutation P operations to improve security. Based on the security rule, the cipher should not use consecutive substitutions or consecutive permutations. In the following combinations, which one violates the above security rule?

?₁?₁?₂?₂

B. ?₁?₁?₂?₂

C. ?₁?₁?₂?₂

4, Which description about the DES cipher is NOT correct?

The block size of DES is 64 bits.
The DES cipher is based on the Feistel Cipher Structure.
When the plaintext is encrypted using DES twice (Double DES) with two different keys, the key search space increases from 2⁵⁶ to 2¹¹².
Triple DES is more secure compared with original DES.

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