CEH Practice Question: Advanced Topics: Wireless, Cloud, IoT, Cryptography

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

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  RC4

  Why it's wrong here

  RC4 is classified as a symmetric stream cipher, not a block cipher. Unlike block ciphers that process data in fixed-size chunks, RC4 generates a pseudorandom keystream that is XORed with the plaintext, encrypting data bit by bit or byte by byte. This fundamental difference means it does not operate with a fixed block size, making it distinct from algorithms that encrypt discrete blocks of data.

• ✗

  3DES

  Why it's wrong here

  Triple DES (3DES) is indeed a symmetric block cipher, but it operates on a fixed block size of 64 bits, not 128 bits. While 3DES applies the DES algorithm three times with either two or three distinct 56-bit (effective) keys to enhance security, its underlying data processing unit remains 64 bits. Therefore, it does not meet the criteria for a 128-bit block size often associated with modern symmetric encryption standards.

• ✓

  AES

  Why this is correct

  Advanced Encryption Standard (AES) is the correct answer because it is a symmetric block cipher that processes data in fixed-size blocks of 128 bits. AES supports various key sizes, including 128, 192, and 256 bits, providing strong security. Its design as a robust and efficient block cipher has established it as the global standard for symmetric encryption, fulfilling both the symmetric classification and the 128-bit block size requirement.

• ✗

  RSA

  Why it's wrong here

  RSA (Rivest–Shamir–Adleman) is an asymmetric cryptographic algorithm, also known as public-key cryptography. Unlike symmetric algorithms that use a single shared secret key for both encryption and decryption, RSA employs a pair of mathematically linked keys: a public key for encryption and a private key for decryption. This fundamental distinction immediately disqualifies it as a symmetric algorithm, regardless of its block processing characteristics.

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