When an Identity Provider authenticates a user and directs them back to the referring Service Provider, it includes as part of the message an assertion to prove that the user authenticated. See also Identity Provider, Service Provider.
A piece of data produced by a SAML authority regarding either an act of authentication performed on a subject, attribute information about the subject, or authorization data applying to the subject with respect to a specified resource. This Assertion is used in access control and audit trails.
An assertion is data, produced by a SAML authority, constituting a declaration of identity, or attribute information, or authorizations.