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What is machine-to-machine authentication?
Machine-to-machine authentication (also sometimes called machine to machine communication) is the authorization of communication and access to resources between applications – all without any human involvement in the process. With M2M authentication, clients (i.e. an application, process, or autonomous system) can communicate and operate autonomously to execute business functions without the need for a user to interact with the system to authenticate and authorize a client.
A common way to implement M2M is with OAuth 2.0 (this is what the Stytch M2M product uses!).
What are common use cases of machine-to-machine authentication?
Examples of communications that might require M2M authentication include communication with backend application servers, continuous processes like daemons and job schedulers, Command Line Interfaces (CLIs), Internet of Things (IoT) devices, external APIs, and more.
How does machine to machine authentication work?
Because machine-to-machine authentication relies on OAuth 2.0, its flow will be slightly reminiscent of the authorization code flow, in the sense that the authorization server is fielding requests to access a company's API. BUT, there are a few key differences, specific to the client credentials grant flow that are worth noting:
- In step one, an application or machine sends a request to the authorization server in the form of a client credentials grant request, including at the very least grant_type and client_authentication information, and as many claims as the application deems necessary.
- If the client_authentication information that's passed along is correct, the authorization server will validate the request, and return an access token (typically in the form of a JWT).
- The application can now use that access token to get access to the resources specified in the initial request.
What is a client credentials grant? Why does it matter for M2M?
The client credentials grant refers to a type of OAuth 2.0 grant that is used to provide an application secure access to its own resources. Just like authorization code grants are used for users, client credentials grants are used for machine-to-machine authorization and authentication.
The client credentials grant includes three main parameters you may recognize from other OAuth 2.0 grant types:
- grant_type (required): As you can guess, this should be set to client_credentials.
- client_authentication (required): Just like you'd authenticate a user, client authentication typically includes the parameters by which an application authenticates itself, namely its client ID (client_ID) and the client secret (client_secret).
- scope (optional): Like with any OAuth 2.0 grant, the scope in a client credentials grant is where you can specify the exact resources to which the resource owner is granting access.
These parameters are included in the initial client credentials grant request. If the client ID and client secret in the request match the server's record, this type of grant request results in the exchange of an access token, which can then be used by the application to gain access to your API's resource server.
Why is Zero Trust so important?
Since companies began transitioning from on-premises (on-prem) facilities to remote systems, cybersecurity specialists have known that user authentication was not enough to safeguard protected resources.
The premise of Zero Trust is somewhat simple: assume that no user, application, or machine can be trusted – even if they're already on a private network.
On the one hand, this may seem like more work, as it involves a lot more authentication and authorization protocols. You don't just need to regularly authenticate all users, applications, and machines – you also need to regularly check that no single party is authorized to access more resources than they absolutely have to in order to perform their function. This kind of monitoring and verification is ongoing.
On the other hand, by integrating greater rigor into authentication across apps, endpoints, and identities, you are much less likely to fall victim to more sophisticated attacks – which in the end saves you time, money, and an earned reputation with your clients.