US Patent 9578015 Step-up authentication for single sign-on

A method for authenticating a user seeking access to first and second resources that have different authentication levels. The method includes receiving a primary token that is associated with a first authentication event of the user and authenticates the user to access the first resource, and receiving a first request to access the second resource. The method further includes receiving first credentials of the user. The method further includes, responsive to validating the first credentials, generating a second authentication event, associating the second authentication event with the primary token, and issuing a first secondary token that authenticates the user to access the second resource.