Auth Provider mechanisms

http://www.mythics.com/about/blog/what-to-consider-when-integrating-authentication

some basic terminology around authentication:
1. Identity – Describes who you are.
2. Credential – Something that proves who you are.
3. Identity Provider – A trusted system that collects your credentials and provides your validated identity to a service.
4. Service Provider – Some kind of service provided to the user that requires knowledge of the user's identity.
5. Trust – How does a service provider establish the integrity of an identity provider?

Protocol	Identity	Credential	Identity Provider	Service Provider	Trust
SAML2	XML "Assertion"	Multiple	SAML2 Identity Provider	SAML2 Service Provider	Established by digitally signing assertions of identity with pre-shared keys or pre-trusted certificate authorities
OAuth	JSON "Token"	Multiple but current standards for specifying	OAuth endpoint	OAuth endpoint	OAuth verified identity providers using pre-shared "tokens" that are hard to guess, but not cryptographically verified
SSL Certificate Authentication	Digitally signed certificate	Digitally signed certificate	Certificate authority	Web server running SSL	Established through the trust of certificate authorities
BrowserID	Email address	Certificate	BrowserID provider	Any web application	Trust is established when a user is granted a certificate for authentication from their email provider