You have been assigned the task of selecting a hash algorithm. The algorithm will be specifically used to ensure the integrity of certain sensitive files. It must use a 128 bit hash value. Which of th

Question

Options

• AAES
• BSHA
• CMD5
• DDES

• A
  3% (1)
• B
  6% (2)
• C
  91% (29)

Explanation

MD5 (Message Digest 5) is correct because it is a hashing algorithm that produces exactly a 128-bit hash value, making it the only option that satisfies the specific bit-length requirement for integrity verification.

Why the distractors are wrong:

• AES (A) is a symmetric encryption algorithm used for confidentiality, not hashing - it encrypts/decrypts data rather than producing a fixed-length digest.
• SHA (B) is a valid hashing algorithm family, but standard SHA-1 produces 160-bit hashes, and SHA-256/384/512 produce even larger outputs - none match 128 bits.
• DES (D) is another symmetric encryption algorithm (like AES), not a hashing function at all; it operates on 64-bit blocks for encryption.

Memory tip: Think "MD5 = 128" - both have the number 5 in them, and 128 = 2^7 (close enough to remember it's the smaller, older digest). Alternatively, note that MD5 ends in "5" and 1+2+8 = 11 → just memorize "MD5 is the mini digest at 128 bits."

Note for exam context: While MD5 is the textbook answer here based on bit length, be aware that MD5 is considered cryptographically broken and should not be used in real-world security implementations - SHA-256 or better is recommended in practice.

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