In a general aspect, orientation information is used to generate a unique code. In some aspects, orientation information is extracted from an object. The object includes multiple elements, and the orientation information indicates the relative spatial orientations of the respective elements. The orientation information can be extracted, for instance, by a scanner system that detects the elements. A unique code is generated for the object based on the orientation information. In some examples, the elements are diamond particles that each have one or more color centers, and the orientation information is extracted by detecting the color centers.