With so many servers running independently of each other on the etags network, there needs to be a way to give a server permission to access parts of a user’s social networking profile, without handing over the entirety of a user’s account. There also needs to be a way for the servers to allow services (such as social networks) to use the tag data provided by users, or to add a tag of a user, again without needing to have full control. The solution to this problem is OAuth.
OAuth is an open protocol which allows a user to give restricted access to a resource to a consumer. It is already supported by all of the major social networks (including Facebook which uses OAuth2 in Facebook Connect) and it seems unlikely that future social networks will be created without using OAuth
In the case of etags, each server will act as a consumer to the existing social networks, this is to access the user’s photographs and tags which may be stored there already, to publish new tags to the user’s feed (or “wall”) and simply to identify users across different social networks. The servers will also act as a provider to any clients which wish to access the tags stored in etags.
Due to the very wide support of OAuth there are a large number of libraries available to use as both a consumer and provider. For the prototype (and possibly reference implementation) of etags, the python-oauth2 library will be used.