OAuth (Open Authorization)
- What is OAuth, and how does it work for authorizing third-party applications to access user data?
- How does OAuth 2.0 differ from OAuth 1.0?
- What are the roles in OAuth, such as Authorization Server, Resource Server, Client, and Resource Owner?
- Explain the Authorization Code Flow in OAuth. When should it be used?
- What is the difference between the Implicit Flow and Authorization Code Flow in OAuth?
- Explain how the Client Credentials Flow works in OAuth 2.0 and when it is appropriate to use it.
- How does the Resource Owner Password Credentials Flow differ from the other OAuth flows?
- What is the purpose of Scopes in OAuth, and how are they used in a real-world application?
- What are refresh tokens, and how do they contribute to OAuth security and usability?
- How does OAuth 2.0 handle token expiration and token revocation?
- How would you handle token theft in an OAuth system?
- Explain the concept of OAuth tokens (access token, refresh token) and their lifecycle.
- How can you secure communication between OAuth clients and authorization servers?
- What is PKCE (Proof Key for Code Exchange), and how does it enhance security in OAuth 2.0?
- What are OAuth Scopes, and how do they limit the permissions granted to third-party applications?
- How do you implement OAuth2 with PKCE in mobile and web applications for improved security?
- What are the main vulnerabilities in OAuth 2.0, and how can you mitigate them?
- What are the best practices for implementing OAuth 2.0 in a distributed system?
- Can OAuth be used for single sign-on? If so, explain how.
- How do you implement OAuth2.0 with API Gateway and manage access control?
JWT (JSON Web Tokens)
- What is JWT, and how does it fit into the authentication and authorization process?
- What are the key components of a JWT, and how is it structured (header, payload, signature)?
- How does JWT work in conjunction with OAuth 2.0?
- Explain the different JWT signing algorithms, such as HMAC, RSA, and ECDSA.
- What is the purpose of JWT expiration (exp), and how does it improve security?
- What are JWT claims, and what are the most commonly used claims like iss, sub, and aud?
- What is the difference between stateless and stateful JWT authentication?
- How does JWT refresh tokens work, and how can they be used to maintain user sessions?
- How do you validate JWT tokens on the server side and ensure they are not tampered with?
- What are the potential risks of JWT-based authentication? How do you mitigate them?
- How would you implement JWT token-based authentication in a microservices architecture?
- How can you invalidate JWT tokens (because they are stateless, they cannot be invalidated directly)?
- Explain how to handle JWT signature verification and audience (aud) verification.
- How do you implement JWT token rotation for improved security?
- How does JWT compare to session-based authentication in terms of security, scalability, and usability?
- What are the best practices for storing JWTs in web applications and mobile apps?
- What is JWT front-end storage, and how do you securely manage JWT in the client (localStorage, cookies)?
- How do you implement JWT token expiration and refresh in a single-page application (SPA)?
- What are the common vulnerabilities associated with JWT tokens, and how do you mitigate them?
- Explain the importance of secure key management for signing JWT tokens.
OpenID Connect
- What is OpenID Connect (OIDC), and how does it differ from OAuth 2.0?
- How does OpenID Connect extend OAuth 2.0 to provide authentication?
- What is the role of the ID Token in OpenID Connect?
- How does OpenID Connect enable single sign-on (SSO) across multiple applications?
- What are the key components of an OpenID Connect flow?
- Explain the concept of UserInfo endpoint in OpenID Connect.
- How does OpenID Connect handle consent in the authorization process?
- What is the role of scopes in OpenID Connect, and how do they affect the authentication process?
- How does OpenID Connect support federated identity and cross-platform authentication?
- How do you implement OpenID Connect in a mobile or web application for user authentication?
- What is discovery document in OpenID Connect, and how does it simplify configuration for clients?
- How would you handle logout and session management in OpenID Connect?
- What is ID Token Validation in OpenID Connect, and how do you verify its authenticity?
- How does OpenID Connect enhance security compared to traditional username/password authentication?
- What are OIDC response types, and how do they affect authentication flows?
- Explain the concept of Hybrid Flow in OpenID Connect.
- How does OpenID Connect manage multiple clients with different redirect URIs?
- How do you implement token revocation and session expiration in OpenID Connect?
- What are the common vulnerabilities associated with OpenID Connect, and how can they be mitigated?
- How can you integrate OpenID Connect with OAuth 2.0 for enterprise-level single sign-on (SSO)?
Advanced Authentication Topics
- How would you implement multi-factor authentication (MFA) with OAuth, JWT, and OpenID Connect?
- Explain the concept of delegated authorization in OAuth 2.0 and OpenID Connect.
- How do you manage token security when interacting with public and private APIs?
- How would you ensure secure storage of OAuth tokens and JWT in client applications?
- What is token exchange, and how do you implement it securely in OAuth 2.0?
- How do you implement OAuth in a microservices architecture with secure token propagation?
- How do you manage user consent and authorization policies in an OAuth/OpenID Connect system?
- What is the Refresh Token Grant in OAuth, and how does it improve usability?
- How do you implement token introspection in OAuth 2.0?
- What is the difference between access tokens and ID tokens, and how are they used differently in authentication and authorization?
Security Considerations and Best Practices
- How do you protect OAuth/OpenID Connect endpoints from cross-site request forgery (CSRF) attacks?
- How do you handle man-in-the-middle (MITM) attacks when transmitting OAuth and OpenID Connect tokens?
- What is token leakage, and how can you protect against it?
- Explain the importance of PKCE (Proof Key for Code Exchange) and how it enhances OAuth 2.0 security.
- How do you secure JWT tokens stored in localStorage and sessionStorage?
- How would you implement two-factor authentication (2FA) using OAuth/OpenID Connect?
- What are the best practices for signing algorithms in JWT, and which one do you recommend for production?
- How do you ensure token integrity during transmission in OAuth/OpenID Connect systems?
- How do you implement audience (aud) validation in JWT tokens?
- What are the risks of using self-signed certificates in OAuth/OpenID Connect systems, and how do you mitigate them?
Scalability and Performance
- How do you implement scalable authentication systems using OAuth and OpenID Connect?
- How can you optimize the performance of JWT validation in high-traffic applications?
- How do you design a token revocation mechanism for scalable systems?
- How does OAuth 2.0 handle high-volume API requests while maintaining security?
- What are the best practices for OAuth token expiration and refresh strategies in distributed systems?
- How do you optimize OAuth flows for mobile devices and low-bandwidth environments?
- How do you ensure token reliability in a multi-region microservices architecture?
- What are the trade-offs between stateful and stateless authentication systems?
- How can you implement single sign-out across multiple services in an OAuth/OpenID Connect system?
- What is the impact of OAuth/OpenID Connect on application latency, and how can it be minimized?
Real-World Scenario Questions
- How do you implement OAuth/OpenID Connect for a single-page application (SPA)?
- Explain how you would handle third-party authentication via OAuth 2.0 in a SaaS application.
- How do you handle OAuth token validation in a microservices architecture?
- How would you ensure user privacy in an OAuth/OpenID Connect-based authentication system?
- What are the challenges of implementing cross-origin resource sharing (CORS) with OAuth tokens?
- How do you implement OAuth2 authorization code flow in a mobile app?
- How would you configure OAuth/OpenID Connect for a cloud-native environment?
- How do you handle OAuth/OpenID Connect integrations with third-party identity providers?
- How do you implement API Gateway for managing OAuth/OpenID Connect flows?
- How do you implement role-based access control (RBAC) in an OAuth/OpenID Connect system?
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