In the begining of "Birthright. Part I" episode (Star Trek Next Generation 6x16) an Yridian tells Worf, that he has a certain information,
that Worf's father is still alive (apparently not killed in Khitomer Massacre) and is held in a prison camp on Carraya IV.
Yridian is an information broker and agrees to reveal details (i.e. location) only for a price.
How or with what Worf would pay for this? There is no economic factor inside the Federation (no money is being used) and I don't recall anything, Worf would have on board Enterprise, that would have enough value for an information this kind.