The correct answer is that the client does not trust the issuing CA. This error occurs because OpenSSL’s s_client command attempts to validate the server’s certificate chain, but the client machine lacks the intermediate or root Certificate Authority certificate in its local trust store, breaking the chain of trust. On the Systems Security Certified Practitioner (SSCP) exam, this scenario tests your understanding of PKI trust models and common TLS troubleshooting—a frequent trap is assuming the error points to an expired or self-signed server certificate, when it actually indicates a missing CA certificate on the client side. Remember, the server’s certificate itself may be perfectly valid; the issue is that your local system cannot verify its issuer. A useful memory tip: “Local issuer missing, trust is missing”—if OpenSSL can’t find the CA locally, it can’t confirm the server is who it claims to be.
SSCP Cryptography Practice Question
This SSCP practice question tests your understanding of cryptography. 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.
Exhibit
Refer to the exhibit.
```
openssl s_client -connect server.example.com:443
CONNECTED(00000003)
depth=0 C = US, ST = California, L = San Francisco, O = Example Inc, CN = server.example.com
verify error:num=20:unable to get local issuer certificate
---
Certificate chain
0 s:/C=US/ST=California/L=San Francisco/O=Example Inc/CN=server.example.com
i:/C=US/O=Example Root CA/CN=Example Root CA
---
Server certificate
-----BEGIN CERTIFICATE-----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```
Refer to the exhibit. An administrator runs an OpenSSL s_client command and receives the output shown. What is the most likely cause of the 'unable to get local issuer certificate' error?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Refer to the exhibit.
```
openssl s_client -connect server.example.com:443
CONNECTED(00000003)
depth=0 C = US, ST = California, L = San Francisco, O = Example Inc, CN = server.example.com
verify error:num=20:unable to get local issuer certificate
---
Certificate chain
0 s:/C=US/ST=California/L=San Francisco/O=Example Inc/CN=server.example.com
i:/C=US/O=Example Root CA/CN=Example Root CA
---
Server certificate
-----BEGIN CERTIFICATE-----
MIIBxTCCAS0CAQAwDQYJKoZIhvcNAQELBQAwHzENMAsGA1UEAwwEUm9vdDEPMA0G
A1UEChMGVGVzdCBDQTAeFw0yNDAxMDEwMDAwMDBaFw0yNTAxMDEwMDAwMDBaMD8x
CzAJBgNVBAYTAlVTMRMwEQYDVQQIDApDYWxpZm9ybmlhMRIwEAYDVQQHDAlTYW4g
RnJhbmNpc2NvMQ0wCwYDVQQDDARUZXN0MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCB
iQKBgQC0Yj1J2K1F1L2y3Y4Z5X6Z7Q8a9b0c1d2e3f4g5h6i7j8k9l0m1n2o3p4
q5r6s7t8u9v0w1x2y3z4A5B6C7D8E9F0G1H2I3J4K5L6M7N8O9P0QCAwEAATAN
BgkqhkiG9w0BAQsFAAOBgQBmJ6k7L8P9Q0R1S2T3U4V5W6X7Y8Z9a0b1c2d3e4f5
g6h7i8j9k0l1m2n3o4p5q6r7s8t9u0v1w2x3y4z5A6B7C8D9E0F1G2H3I4J5K6L7
M8N9O0P1Q2R3S4T5U6V7W8X9Y0Z1a2b3c4d5e6f7g8h9i0j1k2l3m4n5o6p7q8r
```
A
The server's private key is missing.
Why wrong: The s_client output does not indicate private key issues.
B
The client does not trust the issuing CA.
The 'unable to get local issuer certificate' error means the CA is not trusted.
C
The server certificate is self-signed.
Why wrong: The issuer is 'Example Root CA', not the server itself.
D
The server certificate has expired.
Why wrong: The certificate dates are within validity; no expiration error.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The client does not trust the issuing CA.
The 'unable to get local issuer certificate' error from OpenSSL s_client indicates that the client (the machine running the command) does not have the issuing Certificate Authority (CA) certificate in its trust store. This means the client cannot verify the server certificate's chain of trust. Option B is correct because the error specifically points to a missing or untrusted CA certificate on the client side, not a problem with the server's private key, self-signing, or expiration.
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.
✗
The server's private key is missing.
Why it's wrong here
The s_client output does not indicate private key issues.
✓
The client does not trust the issuing CA.
Why this is correct
The 'unable to get local issuer certificate' error means the CA is not trusted.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The server certificate is self-signed.
Why it's wrong here
The issuer is 'Example Root CA', not the server itself.
✗
The server certificate has expired.
Why it's wrong here
The certificate dates are within validity; no expiration error.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse 'unable to get local issuer certificate' with a server-side certificate issue (like expiration or self-signing), when it actually points to a client-side trust store problem.
Trap categories for this question
Command / output trap
The s_client output does not indicate private key issues.
Detailed technical explanation
How to think about this question
OpenSSL s_client attempts to build a certificate chain from the server's leaf certificate up to a trusted root. The 'unable to get local issuer certificate' error occurs when OpenSSL cannot find the intermediate or root CA certificate in its local trust store (e.g., /etc/ssl/certs or the CApath specified with -CApath). This is distinct from a self-signed scenario, where the issuer is the certificate itself, and the error message differs. In real-world PKI, this often happens when an intermediate CA certificate is not included in the server's chain or the client lacks the root CA.
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 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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Cryptography — This question tests Cryptography — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The client does not trust the issuing CA. — The 'unable to get local issuer certificate' error from OpenSSL s_client indicates that the client (the machine running the command) does not have the issuing Certificate Authority (CA) certificate in its trust store. This means the client cannot verify the server certificate's chain of trust. Option B is correct because the error specifically points to a missing or untrusted CA certificate on the client side, not a problem with the server's private key, self-signing, or expiration.
What should I do if I get this SSCP 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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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