OAuth, OpenID…they sound like the same thing and they kind of do vaguely similar things But I’m here to tell you, OAuth is not Open ID. They have a different purpose. I’ve been playing around with OAuth a bit in the past couple weeks and have a grip on what it’s aiming to do and what it’s not aiming to do.
To start with, here’s what OAuth does have in common with Open ID:
They both live in the general domain of security, identity, and authorisation
They are open web standards. Created and evolved by people with an itch to scratch and evolved pragmatically by a loose, fluid, alliance. Think REST, not SOAP. Think Bar Camp, not The 25th Monosemiannual International Convention for the Society of Professionals who Devise Acronyms Quite a Bit.
They both celebrate decentralisation. There is no central Open ID or OAuth server that holds all the security information in the universe (cf Passport). Anyone can set up as a server or a client.
They both involve browser redirects from the website you’re trying to use – the “consumer” website – to a distinct “provider” website, and back again. Meanwhile, those websites talk to each other behind the scenes to verify what just happened.
The user can actively manage the provider website, exerting control over which websites can talk to it and for how long.
With that much in common, the casual observer could be forgiven for confusing them. But they’re different. Not different as in “vying to be the no. 1 standard”, but different as in “they let you do different things”. How so?
Open ID gives you one login for multiple sites. Each time you need to log into Zooomr – a site using Open ID – you will be redirected to your Open ID site where you login, and then back to Zooomr. OAuth lets you authorise one website – the consumer – to access your data from another website – the provider. For instance, you want to authorise a printing provider – call it Moo – to grab your photos from a photo repository – call it Flickr. Moo will redirect you to Flickr which will ask you, for instance, “Moo wants to download your Flickr photos. Is that cool?”, and then back to Moo to print your photos.
