Question

Consider the following statements about symmetric encryption :
A. Same key for encryption and decryption

B. Faster than asymmetric encryption

C. Key distribution is simpler

D. Stream ciphers encrypt one bit byte at a time

E. Block ciphers operate on groups of bits

Choose the correct answer from the options given below :

• A. A, B, C, E only
• B. B, C, D only
• C. A, C, D, E only
• D. A, B, D, E only

Hint:

Symmetric = Shared Key. Asymmetric = Public/Private pair. If you see "Simple Key Distribution," it's referring to Asymmetric/Public-key cryptography!

Answer 1

The Correct Option is D

Symmetric-key cryptography is a type of encryption where the same secret key is shared between the sender and receiver. 1. Evaluating the Statements:
• A (Same Key): True. This is the definition of symmetric encryption.
• B (Performance): True. Symmetric algorithms (like AES) are much faster than asymmetric ones (like RSA) because they use simpler mathematical operations.
• C (Key Distribution): False. Key distribution is the biggest disadvantage of symmetric crypto. Sharing the secret key securely between parties is complex and risky.
• D (Stream Ciphers): True. They process the plaintext continuously, usually one bit or byte at a time (e.g., RC4).
• E (Block Ciphers): True. They divide the plaintext into fixed-size blocks (e.g., 128-bit blocks in AES) and encrypt each block. 3. Result: Statements A, B, D, and E are correct. Statement C is incorrect.