In this case, it looks like your router is trying to perform a SAML V2.0 single sign-on. SAML stands for Security Assertion Markup Language, and is an XML-based standard for communicating identity information between organizations. The primary function of SAML is to provide Internet single sign-on for organizations looking to securely connect to Internet applications that exist both inside and outside the safety of an organization's firewall. When using SAML to connect to a Web-based application, a handshaking dialogue takes place to establish the secure single sign-on; this is known as an HTTP POST profile. Somewhere within this handshake, the requester is missing the private key needed for the protocol.
There are several solutions: You can input the XML string, or the ID value, or provide a private key. How you input this information will be specific to your particular router. It should just be a matter of reading the manual, calling the router manufacturer's tech support team or conducting an Internet search to resolve this problem.
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This was first published in December 2009