As in the previous flow (client to IdP), various operation information is transported between the IdP and RP over the AAA infrastructure, and the same privacy considerations apply. However, in this flow, explicit identity information about the authenticated principal can be sent from the IdP to the RP. This information can be sent through RADIUS headers, or using SAML [RFC7833]. This can include protocol-specific identifiers, such as SAML NameIDs, as well as arbitrary attribute information about the principal. What information will be released is controlled by policy on the IdP. As before, when sending this information through RADIUS headers, all AAA entities on the path between the RP and IdP have the ability to eavesdrop, unless additional security measures are taken (such as the use of TLS for RADIUS [RFC6614]). However, when sending this information using SAML as specified in [RFC7833], confidentiality of the information should be guaranteed, as [RFC7833] requires the use of TLS for RADIUS.