There are several authentication methods commonly used in REST APIs to make them secure. The most common methods are,

Basic Authentication

This is the simplest form of authentication. The client sends a username and password in headers when they make an API call to the server. The server validates the credentials and responds to the client. This is not very secure unless used over the HTTPS protocol.

API Key Authentication

The client must register with the server to obtain an API key. The client then includes this API key in their requests to the server. The server validates the API key and responds accordingly. While this method is simple to implement, it is not secure if the API key is exposed. Additionally, the server must maintain the API key for each client. It requires storage for that.

Token Based Authentication

The client must authenticate by sending a username, password, or API key in the header. The server validates these credentials, generates a token ( often a JWT), and sends it back to the client. The client then uses this token in subsequent requests to the server to access resources. This method is more secure than using API keys or Basic authentication.

The server does not store anything in this approach, as the JWT token contains the user and access grant details.

A JSON Web Token (JWT) is an open standard that enables secure communication between two parties. Data is verified with a digital signature, and encryption ensures security when sent via HTTP.

JWTs have three key components:

Header: Specifies the token type and the signing algorithm.
Payload: Contains information about the token issuer, expiration, and other claims.
Signature: Ensures the message hasn’t been altered during transit with a secure signature.

Session Based Authentication

The client sends an authentication request, providing their username and password. Upon successful authentication, the server generates a unique session identifier (session ID) and stores it in its session store. The server then responds to the client with the session ID.

In subsequent requests, the client includes the session ID in the request headers. The server validates the session ID against its session store to verify the user's identity. If the validation is successful, the server processes the request and responds with the requested data.

Session-based authentication differs from JWT authentication in several key aspects:

Stateful: Session-based authentication is stateful, requiring the server to maintain session information for each user. This can make it less secure and less scalable compared to JWTs.
Security: Session-based authentication can be less secure than JWTs if not implemented properly, as session IDs can be stolen or hijacked.
Scalability: Session-based authentication can be challenging to scale as it requires session synchronization across multiple servers.
On the other hand, JWT authentication is stateless, more secure, and scalable.

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