Question: What are the most common machine authentication methods?

Hey guys,

I'm kinda struggling with the idea of machine authentication in m2m-communication in public networking (like a rest api). What are the most common ways to authenticate machines?

I am aware that 'machines' is a heterogeneous term, since it can refer to services, sensors, probably even gateways/hubs, virtual machines and so on, who may all use different communication protocols.

I have a lot of ideas in my head, like hard coded uid/password combination, certificates in some sort of pki. What's the best practice here, and how are these credentials distributed/stored on devices?

I'm having a hard time categorizing these auth methods in a general way like user authentication.

Some tasty literature would be greatly appreciated if you have recommendations on top of your head.

Cheers