The answer is to ensure the image is an exact bit-for-bit copy and provide an integrity check. The `hash=sha256` parameter instructs dcfldd to compute a SHA-256 hash of the input data as it is read from the source drive, while `hashlog=hash.txt` writes that hash value to a separate log file for later verification. This combination allows an analyst to later recompute the hash of the forensic image and compare it to the stored value, confirming that no data corruption or alteration occurred during acquisition. On the CHFI exam, this question tests your understanding of forensic imaging best practices, specifically how dcfldd differs from dd by offering built-in hashing for integrity verification—a common trap is confusing this with encryption or compression. Remember the memory tip: “Hash on the fly, verify by and by” to recall that dcfldd computes the hash during imaging, not after.
CHFI Computer Forensics Fundamentals and Process Practice Question
This CHFI practice question tests your understanding of computer forensics fundamentals and process. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An analyst performs forensic imaging using the command: dcfldd if=/dev/sda of=image.dd hash=sha256 hashlog=hash.txt bs=4096 conv=noerror,sync. What is the PRIMARY purpose of the 'hash=sha256' and 'hashlog=hash.txt' parameters?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
To ensure the image is an exact bit-for-bit copy and provide an integrity check.
The `hash=sha256` parameter instructs dcfldd to compute a SHA-256 hash of the input data as it is read, and `hashlog=hash.txt` writes that hash value to a separate file. This allows the analyst to later verify that the forensic image (`image.dd`) is an exact bit-for-bit copy of the source (`/dev/sda`) by recomputing the hash and comparing it to the stored value, ensuring data integrity and admissibility in court.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
To encrypt the image file to prevent unauthorized access.
Why it's wrong here
Hashing is not encryption; it is a one-way function for integrity verification.
✗
To compress the image to save disk space.
Why it's wrong here
dcfldd does not compress by default; hashing does not reduce size.
✓
To ensure the image is an exact bit-for-bit copy and provide an integrity check.
Why this is correct
Hashing calculates a digital fingerprint. If the hash matches later, the image has not been altered.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
To split the image into smaller chunks for easier transport.
Why it's wrong here
dcfldd can split with 'split=' parameter, not with hash options.
Common exam traps
Common exam trap: answer the scenario, not the keyword
EC-Council often tests the distinction between hashing (integrity) and encryption (confidentiality), so the trap here is that candidates confuse the purpose of a hash algorithm with that of an encryption cipher, leading them to incorrectly select Option A.
Detailed technical explanation
How to think about this question
Under the hood, dcfldd computes the hash incrementally as data is read from the input device, using the same block size (`bs=4096`) for both reading and hashing, which minimizes memory overhead. In real-world forensic practice, the hashlog file is often stored separately from the image (e.g., on a write-protected medium) to provide a chain of custody verification; if the image is later altered even by a single bit, the SHA-256 hash will differ, immediately flagging tampering.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the CHFI exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CHFI question in full detail.
Computer Forensics Fundamentals and Process — This question tests Computer Forensics Fundamentals and Process — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: To ensure the image is an exact bit-for-bit copy and provide an integrity check. — The `hash=sha256` parameter instructs dcfldd to compute a SHA-256 hash of the input data as it is read, and `hashlog=hash.txt` writes that hash value to a separate file. This allows the analyst to later verify that the forensic image (`image.dd`) is an exact bit-for-bit copy of the source (`/dev/sda`) by recomputing the hash and comparing it to the stored value, ensuring data integrity and admissibility in court.
What should I do if I get this CHFI question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. During a forensic examination, an analyst uses the command 'dcfldd if=/dev/sda of=image.dd hash=sha256 hashlog=hash.txt'. What is the primary purpose of including 'hash=sha256' in this command?
hard
A.To split the image into multiple files named with SHA-256 checksums
✓ B.To compute a SHA-256 hash of the input drive and log it to a file for integrity verification
C.To encrypt the output image file using SHA-256
D.To compress the image using SHA-256 compression algorithm
Why B: Option B is correct because the `hash=sha256` parameter in `dcfldd` instructs the tool to compute a SHA-256 hash of the input device (`/dev/sda`) during the acquisition process. This hash is then logged to the file specified by `hashlog=hash.txt`, providing a verifiable integrity check that the forensic image matches the original source. This is a standard forensic practice to ensure the image has not been altered or corrupted.
Last reviewed: Jun 30, 2026
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This CHFI practice question is part of Courseiva's free EC-Council certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CHFI exam.
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