A method, system, and computer program product for exercising rights based
on determining trust in an issuance of a rights expression, including
issuing rights expressions by a chain of servers, forming a chain of
rights expressions issued from server to server and finally from the last
server to a client, such that each of the rights expressions except the
last includes a specification of rights for the next server to issue the
rights in the next rights expression; determining whether or not each of
the servers has a right to issue the respective rights expression;
exercising by the client the rights expressed in the last rights
expression as being trusted, if it is determined that each of the servers
had a right to issue the respective rights expression; and not exercising
by the client the rights expressed in the last rights expression as not
being trusted, if it is determined that at least one of the servers did
not have the right to issue the respective rights expression.