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SSCP · Question #660

Which of the following statements pertaining to message digests is incorrect?

The correct answer is C. The message digest should be calculated using at least 128 bytes of the file. Message digests (hash values) are typically calculated from the entire input data, regardless of its size, and produce a fixed-size output, making the statement about a minimum 128-byte calculation incorrect.

Submitted by luis.pe· Apr 18, 2026Cryptography

Question

Which of the following statements pertaining to message digests is incorrect?

Options

  • AThe original file cannot be created from the message digest.
  • BTwo different files should not have the same message digest.
  • CThe message digest should be calculated using at least 128 bytes of the file.
  • DMessages digests are usually of fixed size.

How the community answered

(47 responses)
  • A
    2% (1)
  • C
    96% (45)
  • D
    2% (1)

Why each option

Message digests (hash values) are typically calculated from the entire input data, regardless of its size, and produce a fixed-size output, making the statement about a minimum 128-byte calculation incorrect.

AThe original file cannot be created from the message digest.

Message digests are one-way functions, meaning it is computationally infeasible to reverse the hashing process and reconstruct the original data from the digest, upholding its cryptographic security.

BTwo different files should not have the same message digest.

Cryptographic hash functions are designed to be collision-resistant, meaning it should be extremely difficult to find two different inputs that produce the same output hash value, ensuring the uniqueness of the digest for integrity.

CThe message digest should be calculated using at least 128 bytes of the file.Correct

Message digests are calculated from the entire content of a file or message to ensure integrity, not just a minimum of 128 bytes. Using only a portion would undermine the integrity check, as changes outside that portion would go undetected.

DMessages digests are usually of fixed size.

Cryptographic hash functions, such as MD5, SHA-1, SHA-256, etc., produce a fixed-size output, regardless of the size of the input data, which is a defining characteristic of message digests.

Concept tested: Message Digest (Hash Function) properties

Source: https://learn.microsoft.com/en-us/windows/win32/seccrypto/hashing-and-digital-signatures

Topics

#Message Digests#Hash Functions#Cryptography Basics#Data Integrity

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