CISSP Practice Question: Implementing a digital signature system to ensure…

Answer analysis

Option-by-option breakdown

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

• ✓

  Preimage resistance

  Why this is correct

  Preimage resistance is a fundamental security property for digital signatures, ensuring that given a hash value, it is computationally infeasible to find any input message that produces that specific hash. This prevents an attacker from forging a signature by simply generating a new document that hashes to a known, legitimately signed hash, thereby upholding the non-repudiation principle.

• ✗

  Reversibility

  Why it's wrong here

  Reversibility is not a desired property for cryptographic hash functions; in fact, it is the antithesis of their design. Hash functions are specifically engineered to be one-way, meaning it should be computationally infeasible to reconstruct the original input message from its hash output. If a hash function were reversible, the security of digital signatures would be completely undermined, as the original message could be easily recovered, compromising confidentiality and integrity.

• ✓

  Collision resistance

  Why this is correct

  Collision resistance is a critical security property for digital signatures, demanding that it is computationally infeasible to find two distinct input messages that produce the exact same hash output. This property directly prevents an attacker from creating two different documents, one benign and one malicious, that hash to the same value. Without collision resistance, an attacker could trick a user into signing the benign document and then present the signature as valid for the malicious one, leading to forgery.

• ✓

  Second preimage resistance

  Why this is correct

  Second preimage resistance ensures that given a specific input message and its corresponding hash, it is computationally infeasible to find a *different* input message that produces the identical hash value. This property is paramount for digital signatures as it prevents an attacker from taking an already signed document and substituting it with an alternative, potentially malicious, document that yields the same hash. This safeguards the integrity and authenticity of the originally signed content against targeted replacement attacks.

• ✗

  Determinism

  Why it's wrong here

  Determinism describes the inherent characteristic of a hash function where a specific input will consistently produce the exact same output hash every single time it is processed. While essential for the reliable operation and verification of any hash function, determinism itself is not considered a *security property* in the cryptographic sense. It merely ensures predictable behavior, but does not inherently protect against attacks like finding collisions or preimages, which are the concerns of cryptographic security properties.

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