1. A method of authenticating a product, comprising: capturing an image of a product to be authenticated; determining a plurality of significant points of the captured image; comparing the plurality of significant points of the captured image of the product to be authenticated with a plurality of significant points of a previously captured reference image of a genuine product to determine if the product to be authenticated is the same as the genuine product for authenticating the product; aligning a plurality of said significant points of the image of the product to be authenticated with a plurality of said significant points of the image of the genuine product prior to comparing the significant points, wherein comparing the plurality of significant points of the image of the product to be authenticated with the plurality of significant points of the image of the genuine product comprises determining if a significant point of the plurality of significant points of the image of the product to be authenticated is within a defined distance of a significant point of the plurality of significant points of the image of the genuine product; and determining a total number of significant points of the image of the product to be authenticated which are within said defined distance of a significant point of the image of the genuine product within a region of the image.