Which Technique Strengthens an Encryption Key Against Brute-Force Attacks?
Short answer
A Kevin used key stretching, iterating an initial key through a hardening algorithm to produce an enhanced key resistant to brute-force attacks.
Question
Key Takeaways
The question tests the distinction between key hardening via stretching and adjacent cryptography terms, with the common trap being to choose the broader key derivation function option.
Kevin is using key stretching, which takes an initial key and repeatedly processes it to produce an enhanced key that is intentionally expensive to brute-force. The page confirms why key stretching—not PKI, a generic KDF, or key reinstallation—is the CEH-scoped answer.
Common mistake: Learners often pick key derivation function because KDFs can implement stretching, but the stem’s specific wording about enhancing an initial key into a brute-force-resistant key matches the CEH definition of key stretching.
Expert Analysis
Why the Answer Is Correct
Key stretching directly matches the scenario: Kevin inputs an initial key into an algorithm that deliberately adds computational work—typically repeated hashing or iteration—to produce an enhanced key that is much harder to guess by brute force. The phrase “enhances the security of keys used for encryption and authentication” is the CEH description of key stretching, not certificate trust management or attack recovery. Each brute-force attempt becomes significantly more expensive because the attacker must repeat the stretching process for every candidate key. This is why key stretching is used for password-derived keys and other low-entropy key material.
Why the Other Options Are Wrong
Public key infrastructure manages certificates, certificate authorities, and trust chains; it does not take an initial key and generate a hardened derived key for brute-force resistance. Key derivation function is closely related and can be used to implement stretching, but in the CEH taxonomy the specific technique described—turning an initial key into an enhanced key for encryption and authentication—is key stretching, while KDF is the broader primitive. Key reinstallation is a vulnerability or attack condition, such as reusing a nonce in wireless handshakes, not a technique for strengthening encryption keys. The option set therefore separates a concrete hardening method from unrelated or broader cryptography concepts.
Community Comment Notes
insaniunt described key stretching as increasing “the computational difficulty of deriving the original key,” which aligns with the CEH answer and the brute-force resistance in the stem. shaody emphasized that the initial key is given as input to an algorithm that produces an enhanced key, matching the question’s wording almost exactly. ariel004 argued for a key derivation function, which is the main distractor because KDFs and key stretching overlap conceptually, but the CEH-scoped answer remains key stretching. LordXander simply cited the CEHv12 question reference, confirming this is a known exam item rather than a novel edge case.
Official Reference
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Exam Strategy
When a CEH question describes turning an initial key into an enhanced, brute-force-resistant key, first look for key stretching before choosing the broader KDF term. Read the stem for the phrase “encryption and authentication,” which is a strong clue toward the textbook key-stretching definition.
Frequently Asked Questions
Why is key derivation function (C) not the best answer if KDFs can stretch keys?
Does key stretching make encryption keys immune to brute-force attacks?
Community Votes
100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 4 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 4
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insaniunt 👍 2 Answered AA. Key stretching Key stretching is a technique that increases the computational difficulty of deriving the original key, making it more resistant to brute-force attacks. It is commonly used to enhance the security of passwords and encryption keys.
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ariel004 👍 1C: Based on the description provided, Kevin employed a technique called a key derivation function (KDF) to enhance the security of encryption keys. A KDF is a cryptographic algorithm that takes an input key and generates a derived key that is resistant to brute-force attacks.
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shaody 👍 1 Answered AIn the key stretching technique, the initial key is given as input to an algorithm that generates an enhanced key. The key must be sufficiently resistant to brute-force attacks.
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LordXander 👍 2 Answered ACEHv12 - 3462
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