10 Questions
What is the purpose of the Key Schedule algorithm in DES?
To generate the 16 subkeys used in the 16 rounds of DES encryption
In the DES decryption process, which operation is performed first?
Perform the 16 rounds of the Feistel network in reverse order
What is the purpose of the Avalanche Effect in DES?
To ensure that a small change in the plaintext results in a large change in the ciphertext
What is the purpose of the Feistel design in DES?
To allow the same algorithm to be used for both encryption and decryption, with only a change in the order of the subkeys
What was one of the main factors that led to the eventual replacement of DES with more secure algorithms like AES?
The small key size of DES (56 bits), which made it vulnerable to brute-force attacks as computing power increased
In the DES encryption process, what is the purpose of the initial and final permutations?
To increase the diffusion and confusion of the plaintext and ciphertext
What is the purpose of the expansion permutation in the Feistel function of DES?
To expand the 32-bit half-block to 48 bits, allowing each bit to be used in multiple S-box calculations
Which of the following is a weakness of the Electronic Codebook (ECB) mode of operation in DES?
Repetitions in the plaintext are reflected in the ciphertext, making it vulnerable to code-book analysis
What is the purpose of the Initialization Vector (IV) in the Cipher Block Chaining (CBC) mode of operation in DES?
To provide a unique starting value for the chaining process, preventing patterns in the ciphertext
Which of the following is a strength of the Cipher Feedback (CFB) mode of operation in DES?
The encryption process is computationally efficient for streaming data
Learn about the concept of substitution-permutation ciphers and S-P networks in cryptography. Explore how Claude Shannon introduced the idea of modern block ciphers based on these concepts in 1949.
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