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The intent of this section is to nail down implementation details regarding the ECP plugin. This walkthrough assumes no previous authentication has taken place
Sample Walkthrough
ECP augments outgoing requests
...
Accept: ..., application/vnd.paos+xml
PAOS: urn:
Service Provider responds with 'application/vnd.paos+xml' document
ECP caches relevant data for later interactions with the Identity Provider
ECP may at this point consult the User to choose an Identity Provider from previous interactions or from Service Provider supplied list
ECP sends out stripped-down request to the Identity Provider
Identity Provider (at some point) responds with 'text/xml' document, containing AuthnResponse
ECP verifies AuthnResponse has corresponding cached AuthnRequest
ECP composes new message to Service Provider, including cached RelayState info
Service Provider responds by returning content from original request