Abstract: In a general aspect, identity markers containing identity-forming particles are created by electrostatic printing processes. In some aspects, a toner mixture is received on an electrostatically charged surface of an image transfer drum in an electrostatic printer system. The toner mixture includes fusible particles and diamond particles. The toner mixture is held to the electrostatically charged surface by an electrostatic force. The toner mixture is transferred onto a substrate from the electrostatically charged surface of the image transfer drum. The toner mixture is bonded to the substrate by operation of a fuser assembly of the electrostatic printer system. When the toner mixture is bonded onto the substrate, the fusible particles fuse to each other, thereby forming a host matrix that secures the diamond particles at fixed locations in the host matrix.