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AI / Core OpenAI Codex Application Fundamentals Interview Questions

What are OpenAI's key API authentication and security concepts?

Proper authentication and security practices are fundamental to building production OpenAI applications. Mistakes here can lead to credential exposure, unexpected costs, or data breaches.

import os
from openai import OpenAI

# 1. NEVER hardcode API keys - use environment variables
client = OpenAI(
    api_key=os.environ.get("OPENAI_API_KEY"),   # required
    organization=os.environ.get("OPENAI_ORG_ID"),  # optional
    project=os.environ.get("OPENAI_PROJECT_ID"),   # optional
)

# 2. Project API keys (recommended over user keys)
# Create per-project keys at: platform.openai.com/api-keys
# Scoped to a specific project - limits blast radius on leak

# 3. Organisation structure for teams:
# Organisation > Projects > API keys (per project)
# Rate limits and costs tracked per project

# 4. Service accounts (enterprise)
# Use service account keys for production, not personal user keys

# 5. IP allowlists (available in API settings)
# Restrict which IPs can use an API key

# 6. Codex CLI authentication options:
# a) API key: OPENAI_API_KEY env var
# b) ChatGPT sign-in: codex auth  (auto-generates key for ChatGPT subscribers)

Authentication best practices
PracticeReason
Use environment variablesNever expose keys in code, logs, or repositories
Use project-scoped API keysLimits blast radius if a key is leaked - only one project is affected
Rotate keys regularlyLimits exposure window from undetected leaks
Set spending limitsPrevents runaway costs from bugs or abuse
Enable IP allowlistsPrevents use from unexpected network locations
Use service accounts in prodPersonal user keys tied to employment - service accounts are stable

OpenAI never charges for API key creation. Billing is based on tokens consumed. Set monthly spend limits in the organisation settings to prevent unexpected charges during development.

What is the most important security rule for managing OpenAI API keys in code?
What is the advantage of using project-scoped API keys over organisation-level user keys?

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