Contract IDs.
Xbox: 3-30-3510515-54 (thank you, @Euler13)
PlayStation: 2-30-800-2493-22
Hussein Oam is the dude right next to the evidence in the facility.
Da Yin is one of the dudes in the first checkpoint room (the place right next to the two guards, the woman worrying about her coffee machine, and the two fast food workers).