CHFI Computer Forensics Fundamentals and Process Practice Question

Answer analysis

Option-by-option breakdown

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

• ✓

  SHA-256

  Why this is correct

  SHA-256, a member of the SHA-2 family, produces a 256-bit digest and is currently considered cryptographically secure for integrity verification. In forensic imaging, it is the de facto standard because it is collision-resistant and preimage-resistant, meaning it is computationally infeasible to find two different data sets with the same hash or to reconstruct original data from the digest. Tools such as EnCase, FTK, and dd with sha256sum use it to validate that a forensic image is a perfect bit-for-bit copy of the original medium.

• ✗

  SHA-1

  Why it's wrong here

  SHA-1 generates a 160-bit hash and was widely used in forensic tools, but it now has demonstrated collision attacks, notably the SHAttered attack where two distinct PDFs share the same digest. Because the National Institute of Standards and Technology (NIST) has deprecated SHA-1 for cryptographic use, relying on it in forensic imaging risks allowing an attacker to manipulate evidence while preserving the hash value. Consequently, professional forensic practices have moved to SHA-256 for tamper-evident integrity checks, with SHA-1 only appearing in legacy artifacts.

• ✗

  CRC32

  Why it's wrong here

  CRC32 is a 32-bit cyclic redundancy check used primarily for detecting accidental errors in data transmission or storage, not for detecting intentional tampering. It is not a cryptographic hash function because it lacks key properties such as preimage resistance, and it is trivial to craft an alternate data block that yields the same CRC32 checksum. In forensic imaging, CRC32 can verify that a copy matches a source under benign conditions, but it offers no protection against an adversary who can deliberately modify evidence while recalculating the checksum, so it is unsuitable for evidentiary integrity.

• ✗

  MD5

  Why it's wrong here

  MD5 computes a 128-bit message digest and was popularized in forensic tools for its speed and simple implementation, but it now has well-known practical collision attacks, including chosen-prefix collisions that allow an attacker to create two files with identical MD5 hashes. Such collisions undermine the fundamental evidentiary guarantee that a hash uniquely identifies the original data, because a maliciously substituted file could match the recorded hash. Thus, while MD5 may still be found in legacy forensic workflows or for non-security checks, it is no longer acceptable for court-admissible forensic integrity verification.

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