Quick Answer
The correct command is `gpg --verify file.sig`. This works because a detached GPG signature is a separate file containing only the cryptographic signature, and GPG automatically looks for the original file with the same base name in the same directory—so `file.sig` is checked against `file`—using the signer’s public key from your local keyring to confirm both authenticity and integrity. On the CompTIA Linux+ XK0-005 exam, this question tests your ability to distinguish between signing, encrypting, and verifying operations; a common trap is confusing `--verify` with `--decrypt` or forgetting that the original file must be present and unmodified. Remember the mnemonic: “Sig verifies the file, not the other way around”—the signature file is the argument, and GPG handles the rest.
This XK0-005 practice question tests your understanding of security. 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.
A security engineer needs to verify the authenticity of a downloaded file using its detached GPG signature (file.sig). Which command should be used?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
gpg --sign file
Why wrong: This creates a signature, not verify.
gpg --list-keys
Why wrong: This lists public keys in the keyring, does not verify files.
gpg --verify file.sig
This command verifies the detached signature file.sig against the original file (file).
gpg --decrypt file.gpg
Why wrong: This decrypts a symmetrically encrypted file, not for verifying signatures.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
gpg --verify file.sig
The `gpg --verify file.sig` command is used to verify the authenticity of a file using its detached GPG signature. The detached signature file (file.sig) contains the cryptographic signature, and GPG checks it against the original file (which must be present in the same directory with the same base name) using the signer's public key from the local keyring. This confirms that the file was signed by the holder of the corresponding private key and has not been tampered with.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
gpg --sign file
Why it's wrong here
This creates a signature, not verify.
gpg --list-keys
Why it's wrong here
This lists public keys in the keyring, does not verify files.
gpg --verify file.sig
Why this is correct
This command verifies the detached signature file.sig against the original file (file).
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
gpg --decrypt file.gpg
Why it's wrong here
This decrypts a symmetrically encrypted file, not for verifying signatures.
Common exam traps
CompTIA often tests the distinction between detached signatures and embedded signatures, where candidates mistakenly think `--verify` requires the original file as an argument, but GPG automatically infers it from the signature filename.
Detailed technical explanation
When verifying a detached signature, GPG uses the original file's hash (computed with the same algorithm used during signing) and the signer's public key to check the signature's cryptographic validity. The signature file (.sig) is typically binary or ASCII-armored, and GPG automatically looks for the original file by stripping the .sig extension. In real-world scenarios, this is commonly used to verify software downloads from official repositories, where the signature file is distributed separately to prevent tampering.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Security — This question tests Security — Read the scenario before looking for a memorised answer..
The correct answer is: gpg --verify file.sig — The `gpg --verify file.sig` command is used to verify the authenticity of a file using its detached GPG signature. The detached signature file (file.sig) contains the cryptographic signature, and GPG checks it against the original file (which must be present in the same directory with the same base name) using the signer's public key from the local keyring. This confirms that the file was signed by the holder of the corresponding private key and has not been tampered with.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This XK0-005 practice question is part of Courseiva's free CompTIA 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 XK0-005 exam.
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