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Top 4 API Authentication Methods | The Ultimate Guide

Navdeep Singh Gill | 01 November 2022

What is an API?

The API stands for Application Programming Interface. It is an application interface that allows two applications to communicate. In other words, it is a messenger that brings your request to the provider whom you are requesting and returns a response. It defines functions independent of their successive systems, allowing those uses and definitions to differ without risking each other. Therefore, a good makes it easy to improve the system by providing building blocks.

When engineers create code, they do not usually start from scratch. It enable developers to reuse repetitive but complex processes with minimal code. The speed of it that allow developers to build applications is critical to the current pace of application development. Engineers are now more productive than ever when they have to write more code from scratch. They do not have to recreate the wheel with it every time they write a new program. Instead, they can focus on the unique suggestion of their applications while removing all asset functionality from it.

It proxies decouple the app-facing it from your backend services, shielding those apps from backend code changes. Click to explore about, Understanding APIs and proxies

Difference between Authentication and Authorization?

Before I dive into this, let's outline what authentication is, and a lot of significantly, what it’s not. The subject is usually conflated with a closely connected term: authorization. The maximum amount of authentication drives the fashionable web.
The two functions square measure typically tied along in single solutions. However, the simplest way to divide authorization and authentication is to ask: what do they state or prove concerning me?

What is Authentication?

Authentication is once an entity proves an identity. In alternative words, Authentication proves that you simply square measure the UN agency you say you're. This can be like having a driver’s license given by an infallible authority that the requester, like a law officer, will use as proof that implies you're in reality UN agency you say you're.

What is Authorization?

Authorization is a wholly completely different conception, and in easy terms, Authorization is once an entity proves a right to access. In alternative words, Authorization proves you've got the correct to form an invitation. Take into account the subsequent - you've got an operating key card that permits you to open just some doors within the workspace—however, not all of them. An Application Programming Interface would possibly demonstrate you, however, not authorize you to form a specific request.

Testing attempts to connect an application to the web and different APIs. Click to explore about, Testing Tools and Best Practises

What are the best practices?

The below explained are the best practices of REST Application Programming Interface Authentication methods.

HTTP Schemes

The hypertext transfer protocol Protocol conjointly defines hypertext transfer protocol security auth schemes like:

  • Basic
  • OAuth
  • Bearer
  • Digest
  • and others…

We will reassess the 2 most well-liked used nowadays once discussing REST API.

Basic Authentication

HTTP Basic Authentication isn't suggested because of its inherent security vulnerabilities.

This is the foremost simple technique and also the best. With this technique, the sender places a username: countersign into the request header. The username and countersign area unit encoded with Base64 is the Associate in Nursing secret writing technique that converts the username and countersign into a group of Base64 to confirm safe transmission.

This technique doesn't need cookies, session IDs, login pages, and alternative such specialty solutions. Since it uses the hypertext transfer protocol header itself, there’s no would like for handshakes or alternative advanced response systems.

Here’s an Associate in Nursing example of a Basic Auth in a very request header:
Authorization: Basic asD76f8zdCfd47FCya==

Bearer Authentication

Bearer authentication (also called token authentication) is an Associate in Nursing hypertext transfer protocol authentication theme involving security tokens referred to as bearer tokens.

The name “Bearer authentication” will be understood as “give access to the bearer of this token.” The bearer token permits access to a precise resource or universal resource locator and presumably could be a cryptic string, sometimes generated by the server in response to a login request.

The shopper should send this token within the Authorization header once creating requests to protected resources:

Authorization: Bearer asD76f8zdCfd47FCya==

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API Keys

In REST API Security - its keys are widely employed in the business and have become commonplace. However, this technique shouldn't be thought of as honest security live.

Its Keys were created to fix the primary authentication issues with protocol Basic Authentication and various such systems. A newly generated token is assigned to every first-time user during this technique, signifying that the user is thought. Once the user tries to get in the system, their distinctive key (sometimes generated from their hardware combination and information processing information, and alternative times haphazardly way generated by the server which is aware of them) is employed to prove that they’re a similar user as before.

Many Application Programming Interface keys are sent within the question string as a part of the address, making it easier to get for somebody United Nations agency shouldn't have access to that. Please don't place any API keys or sensitive info in query string parameters! a stronger choice is to place its key within the Authorization header. That’s the projected standard:

Authorization: API key 1234567890abcdef. Yet, in apply keys show up all told types of places:

  • Authorization Header
  • Basic Auth
  • Body Data
  • Custom Header
  • Query String

OAuth (2.0)

OAuth2 combines Authentication and Authorization to permit additional subtle scope and validity management. The previous versions of this specification, OAuth 1.0 and 1.0a, were far more difficult than OAuth 2.0. the necessary amendment within the latest version is that it’s unnecessary to sign every decision with a keyed hash. the foremost common implementations of OAuth use one or each of those tokens instead:

Access token: It permits the appliance to access a user’s data; optionally, access tokens will expire.

Refreshable token: Retrieve a brand new access token if it needs to be expired.
OAuth 2.0 is the most suitable option for distinguishing personal user accounts and granting correct permissions. During this technique, the user logs into a system. That system can then request authentication, sometimes within the style of a token. The user can then forward this request to the Associate authentication server, either rejecting or enabling this authentication. From here, the token is provided to the user, and so to the requester. Such a token will then be checked at any time severally of the user by the requester for validation and may be used over time with a strictly restricted scope and age of validity.

This is a far safer and powerful system than the opposite approaches, primarily as a result of it permits for the institution of scopes which will give access to completely different elements of the Application Programming Interface service and since the token is revoked once a particular time - makes it a lot of more durable to re-use by attackers.

OAuth 2.0 standard Flows

The flows (also referred to as grant types) area unit situations Associate in its shopper performs to induce Associate in Nursing access token from the authorization server. OAuth 2.0 provides many standard flows appropriate for various kinds of Application Programming Interface clients:

Authorization code

The foremost common flow, principally used for server-side and mobile network applications. However, this flow is comparable to users registering for an internet application victimization their Facebook or Google accounts.


This flow needs the shopper to retrieve the Associate access token directly. It's helpful in cases once the user’s credentials can not behold on within the shopper code as a result of a 3rd party will access them. It's appropriate for the net, desktop, and mobile applications that don't embrace any server part.

Resource owner identification

It needs work with a username and identification. Since, in this case, the credentials are a region of the request, this flow is appropriate just for sure shoppers (for example, official applications free by the its provider).

Client Credentials

Supposed for the server-to-server authentication, this flow describes the Associate in Nursing approach once the shopper application acts on its behalf instead of on behalf of somebody user. In most situations, this flow suggests that to permit users to specify their credentials within the shopper application, it will access the resources below the client’s management.

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OpenID Connect

OpenID Connect might be a superficial identity layer on high of the OAuth zero protocol, allowing computing purchasers to verify the identity of associate degree end-user supported the authentication performed by the authorization server and get basic profile data regarding the end-user in a practical and REST-like manner.

In technical terms, OpenID Connect specifies a reposeful hypertext transfer protocol API, victimization JSON as an information format.

OpenID Connect permits a variety of purchasers, together with Web-based, mobile, and JavaScript purchasers, to request and receive data regarding documented sessions and end-users. The specification suite is protrusible, supporting ex gratia options like coding identity information, OpenID suppliers' invention, and session management.

OpenID Connect defines a sign-in flow that allows a shopper application to evidence a user and gets data (or "claims") from this user, like the user name, email, etc. User identity data is encoded in a secure JSON net Token (JWT), referred to as ID token.


JSON net Tokens square measure an open, industry-standard RFC 7519 methodology for representing claims firmly between 2 parties. JWT allows you to decrypt, verify and generate JWT. Whereas JWT might be customary, it had been developed by Auth0.

OpenID Connect defines a discovery mechanism, referred to as OpenID Connect Discovery, wherever an OpenID server publishes its information at a widely known address.

This address returns a JSON listing of the OpenID/OAuth endpoints, supported scopes and claims, public keys accustomed sign the tokens, and different details. The purchasers will use this data to construct a call for participation to the OpenID server. The sphere names and values square measure outlined within the OpenID Connect Discovery Specification.


For now, the clear winner of the four strategies is OAuth 2.0, the measure some use cases during which API keys or communications protocol Authentication strategies could be applicable and therefore the new OpenID connect is obtaining a lot of common, principally as a result of it's supported an already common OAuth 2.0. OAuth 2.0 delivers a lot of advantages, from the convenience of use to a federated system module, and most significantly offers measurability of security – suppliers could solely be seeking authentication at now, however having a system that natively supports study authorization additionally to the baked-in authentication strategies is incredibly valuable, and reduces the price of implementation over the long run.