RESTful API Authentication

Question

I have found quite a few questions on this topic on SO, but couldn\'t find any answering this question:

Should I validate users with their username and password, or with

Answer 1

you can use HTTP Authentication over SSL and that's secure enough. However it makes consumption of API a bit difficult as it requires the client library to support SSL. SSL can affect the performance too if you're expecting too many calls simultaneously.

API key option is just as insecure as HTTP Authentication without SSL. If you're not concerned with security then API Key is the easiest for consumers of the API.