1. A method of verifying, comprising: providing a secure identification document, the secure identification document being made by: mixing a non-reactive material with a covert material to form a plurality of particles; blending the plurality of particles within a substrate polymer material to form a random distribution; capturing a representation of the random distribution; and embedding the representation in a machine readable data carrier within the secure identification document; reading the random distribution of the plurality of particles embedded within the secure identification document; deriving a representation of the read random distribution; reading at least a portion of data stored in the machine readable data carrier within the secure identification document; comparing the derived representation with the read data; and verifying the secure identification document if the derived representative matches the read data.