8. Authentication and authorization for backend engineers TL;DR: This video provides a comprehensive guide to authentication and authorization, their historical evolution, modern implementations, and best practices for backend engineers. The Gist: Topic: Authentication and Authorization for Backend Engineers Core Concept: Authentication: The process of verifying "who are you?" by assigning an identity to a subject (e.g., logging into a platform). , Authorization: The process of determining "what can you do?" by defining capabilities and permissions within a given context (e.g., access rights on a platform). , Both are fundamental for securing modern applications, enabling secure user interactions and controlled resource access. , How it works / Key Concepts & Evolution: Historical Context of Authentication: Early Forms: Began with implicit trust (human vouching, handshakes) in pre-industrial societies, which failed to scale. , Explicit Authentication: Led to the use of physical seals (early tokens, prone to forgery, marking first "bypass attacks") and later passphrases/shared secrets (like early static passwords) with the advent of telegraphy. , , , Digital Era: Mainframes introduced passwords (initially stored in plain text, leading to the development of hashing for secure storage). The 1970s saw an explosion in cryptographic research (Diffie-Hellman, Kerberos) forming the basis of modern protocols. , , , Modern Advancements: The internet's growth necessitated , , Future Trends: Decentralized identity (blockchain), behavioral biometrics, and post-quantum cryptography are emerging as potential future authentication methods , Core Components of Modern Authentication: Sessions: 1919:689eb0903b15696ee57f90e3]] Addresses HTTP's statelessness by establishing temporary server-side context for users. Server creates a unique session ID, stores it with user data (e.g., in Redis or , , 63360:689eb0903b15696ee57f90e3]] JSON Web Tokens (JWTs): A stateless mechanism for securely transferring information between parties as a self-contained, cryptographically signed token. Consists of a Header (metadata), Payload (user data/claims), and Signature (for integrity verification). , Pros: Statelessness (no server-side storage), scalability across distributed systems, and portability. , Cons: Challenges with immediate token invalidation/revocation once issued. Cookies: Small pieces of data stored in a user's browser by the server. Often used to store session IDs or JWTs, automatically sent with subsequent requests to automate the authentication process. , Types of Authentication Workflows: Stateful Authentication: Server maintains user session data (e.g., in Redis) and uses a session ID (often via cookie) to track user state. Offers centralized control and easy revocation. Ideal for traditional web apps. , Stateless Authentication: Relies on self-contained JWTs, where all necessary user information is in the token itself. Highly scalable and ideal for distributed APIs and mobile applications. Token revocation is more complex. , , * , OAuth 2.0 (Open Authorization): A delegation protocol allowing users to grant limited, specific access to their resources on one service (e.g., Google) to another application (e.g., a travel app) without sharing their password. OpenID Connect (OIDC) and OAuth 2.0 serve distinct but complementary purposes in modern web security. While they are often discussed together, understanding their individual roles is crucial. Understanding OAuth 2.0 OAuth 2.0 is primarily an authorization framework. Its core function is to enable a user to grant a third-party application limited access to their resources on another service, without sharing their credentials (like username and password). It focuses on "what you can do" or "what permissions you have" within a platform. For example, when you allow a photo printing app to access your photos on Google Photos, that's authorization handled by OAuth 2.0. OAuth 2.0 was designed to solve the problem of delegating access to resources programmatically. ( , , , ) Understanding OpenID Connect (OIDC) OpenID Connect (OIDC) is an authentication layer built on top of OAuth 2.0. While OAuth 2.0 handles authorization, it does not inherently provide information about the user's identity. OIDC was developed around 2014 to fill this , , , , , ]]) Key Differences and How OIDC Extends OAuth 2.0 The fundamental difference lies in their primary concerns: OAuth 2.0 is for authorization (access delegation), and OIDC is for authentication (identity verification). OIDC extends OAuth 2.0 by introducing a new component called the ID token . This token is typically a JSON Web Token (JWT) and contains essential user identity information, such as the user ID, when they logged in (issued at time), the issuing authority, the user's name, and their email. This ID token allows the client application to verify the user's identity. ( , , , , , ) For instance, when you use "Sign in with Google" on a note-taking application, OIDC is at work. The note-taking app (client) redirects you to Google (authorization server). After , , , , , ) Together, OAuth 2.0 and OpenID Connect have significantly transformed internet security, enabling secure interconnections, resource sharing, and permission management across various platforms. ( , , , ) Would you like a more detailed explanation of the typical workflow of an OpenID Connect-based authentication process?