The answer is non-repudiation. This security goal is achieved because the digital signature is created with the sender’s private key, which only they possess, and verified with their public key, proving both the sender’s identity and that the email was not altered in transit. On the Microsoft SC-900 exam, this concept tests your understanding of how asymmetric cryptography enforces accountability in email communications—a common trap is confusing non-repudiation with authentication or integrity, but remember that non-repudiation specifically prevents the sender from denying they sent the message. A helpful memory tip: think of a digital signature as a unique, unforgeable wax seal—only the sender’s private key can create it, so they cannot later claim the email wasn’t theirs.
SC-900 Practice Question: Describe the concepts of security, compliance, and identity
This SC-900 practice question tests your understanding of describe the concepts of security, compliance, and identity. 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.
A company uses digital signatures on all official emails sent to customers. The signature is created using the sender’s private key, allowing recipients to verify that the email truly came from the claimed sender and that it was not altered in transit. Which security goal is primarily achieved by the digital signature?
Why wrong: Confidentiality ensures data is hidden from unauthorized parties. Digital signatures do not encrypt the message; they only sign it.
B
Integrity
Why wrong: While digital signatures do verify integrity (no tampering), the primary focus of the scenario is preventing the sender from denying the email, which is non-repudiation.
C
Availability
Why wrong: Availability ensures systems and data are accessible when needed. Digital signatures do not contribute to availability.
D
Non-repudiation
Non-repudiation provides proof of origin that cannot be denied. A digital signature created with the sender's private key binds the message to the sender, achieving non-repudiation.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Non-repudiation
Digital signatures use asymmetric cryptography where the sender signs the email with their private key. The recipient can verify the signature using the sender's public key, which proves the identity of the sender and ensures the message has not been tampered with. This directly achieves non-repudiation because the sender cannot deny having sent the email, as only their private key could have created the signature.
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.
✗
Confidentiality
Why it's wrong here
Confidentiality ensures data is hidden from unauthorized parties. Digital signatures do not encrypt the message; they only sign it.
✗
Integrity
Why it's wrong here
While digital signatures do verify integrity (no tampering), the primary focus of the scenario is preventing the sender from denying the email, which is non-repudiation.
✗
Availability
Why it's wrong here
Availability ensures systems and data are accessible when needed. Digital signatures do not contribute to availability.
✓
Non-repudiation
Why this is correct
Non-repudiation provides proof of origin that cannot be denied. A digital signature created with the sender's private key binds the message to the sender, achieving non-repudiation.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse integrity with non-repudiation, but while digital signatures do ensure integrity, the primary security goal they achieve is non-repudiation because they provide cryptographic proof of the sender's identity that cannot be repudiated.
Trap categories for this question
Scenario analysis trap
While digital signatures do verify integrity (no tampering), the primary focus of the scenario is preventing the sender from denying the email, which is non-repudiation.
Detailed technical explanation
How to think about this question
Digital signatures rely on hashing the message content (e.g., using SHA-256) and then encrypting that hash with the sender's private key (e.g., using RSA or ECDSA). The recipient decrypts the hash with the sender's public key and compares it to a locally computed hash of the received message; a match confirms both integrity and authenticity. In real-world email security, protocols like S/MIME or DKIM use digital signatures to provide non-repudiation, which is critical for legal or compliance scenarios where a sender might later dispute sending a message.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this SC-900 question in full detail.
Describe the concepts of security, compliance, and identity — This question tests Describe the concepts of security, compliance, and identity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Non-repudiation — Digital signatures use asymmetric cryptography where the sender signs the email with their private key. The recipient can verify the signature using the sender's public key, which proves the identity of the sender and ensures the message has not been tampered with. This directly achieves non-repudiation because the sender cannot deny having sent the email, as only their private key could have created the signature.
What should I do if I get this SC-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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