Substitution-Permutation Networks in Cryptography

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What is the main reason why Double-DES is not used?

It is more computationally expensive than Triple-DES

It is vulnerable to a meet-in-the-middle attack (correct)

It requires more key material than Triple-DES

It is less secure than Triple-DES

What is the main advantage of using Triple-DES with two keys instead of three keys?

It requires less key material (correct)

It is more secure against brute-force attacks

It is more computationally efficient

It provides better confusion and diffusion properties

What is the main purpose of using an E-D-E sequence in Triple-DES with two keys?

To make the algorithm more resistant to linear and differential cryptanalysis

To increase the effective key size

To ensure that encryption and decryption are equivalent in security (correct)

To provide better confusion and diffusion properties

What is the main difference between Triple-DES with two keys and Triple-DES with three keys?

The key size Signup and view all the answers

Which cryptographic property is most important in preventing the meet-in-the-middle attack on Double-DES?

Diffusion Signup and view all the answers

In which mode does the message get treated as a stream of bits and the output of the cipher is added to the message?

Output Feedback Mode (OFB) Signup and view all the answers

What is the main limitation mentioned for Cipher Feedback Mode (CFB)?

Stalling during block encryption after every n-bits Signup and view all the answers

Which mode uses counter value encryption instead of feedback value encryption?

Counter Mode (CTR) Signup and view all the answers

Why is Triple-DES considered a replacement for DES?

To prevent theoretical attacks that can break DES Signup and view all the answers

What is an advantage of Counter Mode (CTR) over other modes mentioned?

Efficiency in high-speed network encryptions Signup and view all the answers

Which mode requires the sender and receiver to remain in sync and use a recovery method to ensure synchronization?

Output Feedback Mode (OFB) Signup and view all the answers

What concept did Claude Shannon introduce in 1949 that forms the basis of modern block ciphers?

Substitution-Permutation networks Signup and view all the answers

Which cryptographic operation helps provide confusion and diffusion of the message in encryption?

Substitution (S-Box) Signup and view all the answers

What is the main advantage of increasing the key size in a Feistel cipher?

Improves security Signup and view all the answers

How does a Feistel cipher structure partition the input block during encryption?

Into two halves Signup and view all the answers

What operation is performed on the left data half based on the round function of the right half & subkey in a Feistel cipher?

Substitution Signup and view all the answers

What property should an encryption algorithm exhibit for preventing guessing keys effectively?

Avalanche effect Signup and view all the answers

How do S-Boxes contribute to the encryption process?

Map 6 to 4 bits each based on autoclaving Signup and view all the answers

Claude Shannon suggested combining elements to obtain diffusion in encryption. What does diffusion do?

Dissipates statistical structure of plaintext over bulk of ciphertext Signup and view all the answers

What was the significant controversy surrounding the Data Encryption Standard (DES) design despite it being widely used in financial applications?

Choice of a 56-bit key instead of a 128-bit key Signup and view all the answers

What key design principle would help make cipher analysis harder but might also slow down encryption?

Complex round function Signup and view all the answers