- A
OAuth 2.0 client credentials
Why wrong: OAuth is possible but less common for OCI API calls; API key is standard.
- B
SAML 2.0 assertion
Why wrong: SAML is used for federation, not direct API authentication.
- C
Instance principal
Why wrong: Instance principal is for Compute instances to call services without managing keys, but for a microservice, an API key is more portable.
- D
OCI API signing key
OCI API signing key (a key pair) is the standard method for authenticating API requests.
Question 203 of 991
1Z0-1127 Using OCI Generative AI Service Practice Question
This 1Z0-1127 practice question tests your understanding of using oci generative ai service. 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.
Which authentication method should be used to securely call the OCI Generative AI API from a microservice running on OCI Compute?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
OCI API signing key
Option D is correct because the OCI API signing key method uses a pre-generated RSA key pair to sign each HTTP request cryptographically, which is the standard and most secure way to authenticate calls to OCI services, including the Generative AI API, from a microservice running on OCI Compute. This method does not rely on external identity providers or token exchanges, making it ideal for server-to-server communication within OCI.
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.
- ✗
OAuth 2.0 client credentials
Why it's wrong here
OAuth is possible but less common for OCI API calls; API key is standard.
- ✗
SAML 2.0 assertion
Why it's wrong here
SAML is used for federation, not direct API authentication.
- ✗
Instance principal
Why it's wrong here
Instance principal is for Compute instances to call services without managing keys, but for a microservice, an API key is more portable.
- ✓
OCI API signing key
Why this is correct
OCI API signing key (a key pair) is the standard method for authenticating API requests.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common misconception is that instance principal authentication is the default or only secure method for OCI Compute instances, but the exam trap here is that instance principal requires dynamic group configuration and is not the direct authentication method for the OCI API; the API signing key is the explicit, universally supported method for programmatic API calls from any client, including a Compute instance.
Detailed technical explanation
How to think about this question
The OCI API signing key method involves generating an RSA key pair (minimum 2048-bit), uploading the public key to the OCI console for the user or service principal, and then using the private key to sign each HTTP request with the SHA256-RSA signature algorithm as defined in the OCI API signing specification. This ensures request integrity and non-repudiation, and the signed headers include the host, date, and request target, preventing replay attacks. In a microservice scenario, the private key is typically stored securely in a vault or as a secret, and the signing logic is implemented using the OCI SDK's `Signer` class.
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 1Z0-1127 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.
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
What to study next
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FAQ
Questions learners often ask
What does this 1Z0-1127 question test?
Using OCI Generative AI Service — This question tests Using OCI Generative AI Service — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: OCI API signing key — Option D is correct because the OCI API signing key method uses a pre-generated RSA key pair to sign each HTTP request cryptographically, which is the standard and most secure way to authenticate calls to OCI services, including the Generative AI API, from a microservice running on OCI Compute. This method does not rely on external identity providers or token exchanges, making it ideal for server-to-server communication within OCI.
What should I do if I get this 1Z0-1127 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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Last reviewed: Jul 4, 2026
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