CEH Practice Question: Advanced Topics: Wireless, Cloud, IoT, Cryptography
Which of the following is the PRIMARY reason that MD5 is no longer recommended for use in digital signatures?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
MD5 is vulnerable to collision attacks
MD5 is vulnerable to collision attacks, where two different inputs produce the same hash. This undermines the integrity and non-repudiation properties required for digital signatures.
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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MD5 is a symmetric algorithm, not a hash function
Why it's wrong here
MD5 is fundamentally a cryptographic hash function, designed to produce a fixed-size output (a message digest) from variable-size input. It is not a symmetric encryption algorithm, which uses a shared secret key for both encrypting and decrypting data. Hash functions are one-way operations used for integrity verification, whereas symmetric algorithms are two-way, making this statement incorrect.
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MD5 is computationally too slow for large data
Why it's wrong here
MD5 was specifically designed for speed and efficiency in generating message digests, making it computationally fast for processing data of various sizes. Its performance characteristics are generally high, allowing for rapid integrity checks, even on large datasets. Therefore, claiming MD5 is too slow is inaccurate and does not represent its primary security weakness.
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MD5 produces a 128-bit hash, which is too short for modern security
Why it's wrong here
While MD5's 128-bit hash output is indeed considered short by modern cryptographic standards, making it theoretically vulnerable to brute-force preimage attacks over time, this is not its most critical or practically exploited flaw. The primary security concern that led to its deprecation is the practical feasibility of finding collisions, which undermines its integrity guarantees more severely than its output length alone.
- ✓
MD5 is vulnerable to collision attacks
Why this is correct
MD5 is critically vulnerable to collision attacks, where two distinct input messages can be found that produce the exact same 128-bit hash output. Practical methods for generating such collisions have been demonstrated, allowing attackers to forge digital signatures or create malicious files that appear legitimate. This fundamental weakness in its collision resistance makes MD5 unsuitable for security-critical applications requiring integrity verification.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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