API Authentication methods
APIs are used for machine to machine data exchange. When a machine tries to access the data from the application, the machine needs to identify itself. The machines can identify themselves in broadly one of the following ways:
- API Key
- Basic Authentication
- OAuth2 Authentication
API Key
The source application provides a static API key and the caller has to present this API key while fetching the information. Leaking of the API keys is equivalent to leaking of the credentials.
Basic Authentication
In Basic Authentication, the caller needs to present the username and password to access the data.
OAuth2 Authentication
In OAuth2, the caller needs to generate a access token (which is temporary) and pass the generated access token to the application to fetch the data. This is one of the most secure methods to fetch the data.
OAuth2 is a standard spec and the security can be further enhanced with additional properties (Refer to the High Security OAuth in OAuth2 spec)
In addition to security, OAuth2 also allows you to have a fine grained access control on your resources.
Comparison of Authentication types
| Authentication Method | Pros | Cons |
|---|---|---|
| API Key | - Simple to implement and use | - Less secure, keys can be easily shared or exposed |
| - Minimal overhead, fast performance | - Difficult to provide fine-grained access control and permissions | |
| - Compatible with most HTTP clients and servers | - Managing and revoking API keys can be cumbersome | |
| Basic Authentication | - Simple to implement and understand | - Transmits credentials (username and password) in Base64 encoding, which is not secure unless over HTTPS |
| - Supported by most HTTP clients and servers | - Does not provide a way to handle token expiration or revocation | |
| - Not suitable for complex, multi-user systems | ||
| OAuth2 | - Highly secure, supports granular access control with scopes | - Complex to implement and requires more setup |
| - Provides token expiration and revocation mechanisms | - Additional overhead due to token exchange process | |
| - Suitable for third-party integrations and delegated access | - Requires client and server to manage tokens and refresh tokens |
Which Auth method should I use?
Depending upon your application, one or more auth methods might be allowed. Our preference in order of security is:
- OAuth2
- Basic Auth
- API Key
Custom Authentication
We have often seen applications implementing their own authentication methods or the apps being partially compliant with the OAuth2 spec. With custom auth, the users need to be clear of the security impact and the best practices for such methods.