Quick Answer
The correct answer is non-repudiation, because this principle ensures that an entity cannot deny having performed an action, such as signing code. When an attacker uses a stolen certificate to sign malicious code, the cryptographic proof—the digital signature—remains technically valid and tied to the certificate, meaning the legitimate owner cannot deny authorship. This directly compromises non-repudiation, as the signature can no longer be reliably attributed to the intended signer. On the ISC2 Certified in Cybersecurity CC exam, this scenario tests your understanding that non-repudiation relies on the integrity of the private key; a stolen certificate breaks that trust. A common trap is confusing this with authentication or integrity—remember that authentication verifies identity, while non-repudiation prevents denial of action. Memory tip: think “stolen key, no denial”—if the key is stolen, the owner can’t deny the signature.
This CC practice question tests your understanding of security principles. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
After a security breach, it was discovered that an attacker used a stolen certificate to sign malicious code. Which security principle was compromised?
Integrity
Why wrong: Integrity ensures data not tampered, but the issue is authenticity.
Non-repudiation
Correct. The certificate's owner can deny signing the malicious code.
Confidentiality
Why wrong: Confidentiality is about secrecy, not signature authenticity.
Availability
Why wrong: Availability is about system uptime.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Non-repudiation
Non-repudiation ensures that an entity cannot deny having performed an action, such as signing code. When an attacker uses a stolen certificate to sign malicious code, the legitimate owner of the certificate cannot deny the signature, because the cryptographic proof (the digital signature) is bound to the certificate. This compromises the principle of non-repudiation, as the signature can no longer be reliably attributed to the intended signer.
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.
Integrity
Why it's wrong here
Integrity ensures data not tampered, but the issue is authenticity.
Non-repudiation
Why this is correct
Correct. The certificate's owner can deny signing the malicious code.
Related concept
Read the scenario before looking for a memorised answer.
Confidentiality
Why it's wrong here
Confidentiality is about secrecy, not signature authenticity.
Availability
Why it's wrong here
Availability is about system uptime.
Common exam traps
ISC2 often tests the distinction between integrity and non-repudiation, where candidates mistakenly think that a stolen certificate only affects data integrity, but the core issue is the inability to prove who signed the code.
Detailed technical explanation
Digital signatures rely on asymmetric cryptography: the signer uses a private key to create a signature, and anyone with the corresponding public key (embedded in the certificate) can verify it. Non-repudiation is achieved because only the private key holder can generate a valid signature. When a certificate is stolen, the private key is compromised, allowing an attacker to create signatures that appear to come from the legitimate owner, breaking the binding between identity and action. In PKI, revocation mechanisms like CRLs or OCSP can mitigate this, but the non-repudiation of past signatures remains compromised.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
What to study next
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FAQ
Security Principles — This question tests Security Principles — Read the scenario before looking for a memorised answer..
The correct answer is: Non-repudiation — Non-repudiation ensures that an entity cannot deny having performed an action, such as signing code. When an attacker uses a stolen certificate to sign malicious code, the legitimate owner of the certificate cannot deny the signature, because the cryptographic proof (the digital signature) is bound to the certificate. This compromises the principle of non-repudiation, as the signature can no longer be reliably attributed to the intended signer.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This CC practice question is part of Courseiva's free ISC2 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 CC exam.
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