1. A computer implemented method comprising: acquiring digital image data representing an image of at least a portion of a physical object; selecting at least one authentication region of the image data; processing the authentication region data so as to form a digital fingerprint of the object, wherein the digital fingerprint comprises: data identifying at least one object feature within the authentication region, the data including a location of the object feature in the authentication region; for each object feature, data identifying a plurality of locations of interest in the object feature; and for each locations of interest, data identifying at least one fingerprint feature vector that describes a fingerprint feature extracted from the location of interest; and storing the digital fingerprint of the object in an object database.