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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  3DES

  Why it's wrong here

  3DES (Triple DES) is a symmetric block cipher, but it operates with a fundamental block size of 64 bits, inherited directly from its predecessor, DES. While it enhances security by applying the DES algorithm three times with two or three distinct keys, it does not process data in 128-bit blocks. Therefore, it fails to meet the implied criteria of a 128-bit block size.

• ✗

  RC4

  Why it's wrong here

  RC4 is a symmetric encryption algorithm, but it is fundamentally a stream cipher, not a block cipher. Stream ciphers encrypt data one byte or bit at a time by generating a pseudorandom keystream that is XORed with the plaintext. Consequently, RC4 does not have a defined block size, let alone a 128-bit one, making it unsuitable for any requirement specifying a fixed block size.

• ✓

  AES

  Why this is correct

  AES (Advanced Encryption Standard) is the correct answer because it is a symmetric block cipher that processes data in fixed-size blocks of 128 bits. It supports robust key lengths of 128, 192, or 256 bits, providing strong cryptographic security. Its design, based on the Rijndael cipher, makes it highly efficient and widely adopted for various secure communication and storage applications.

• ✗

  RSA

  Why it's wrong here

  RSA is an asymmetric encryption algorithm, which fundamentally distinguishes it from symmetric algorithms. Asymmetric encryption uses a pair of mathematically linked keys—a public key for encryption and a private key for decryption—rather than a single shared secret key. Therefore, RSA does not fit the "symmetric encryption algorithm" requirement of the question, regardless of any block size considerations.

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