1. A method of providing a security document having a security feature, the method including: determining an identity associated with the security document using a sensing device; generating, in the sensing device, a plurality of signature fragments using the identity so that the fragments together define a digital signature of at least part of the identity; generating, in a computer system networked with the sensing device, coded data, the coded data including a number of individual coded data tags, each coded data tag encoding data on: the identity of the security document; and, a respective fragment of the signature; and, printing, with a printer networked with the computer system, the coded data tags on the security document so that the coded data tags are tiled across the security document, wherein the coded data tags are generated and printed so that interaction with only one of the coded data tags to detect the security document identity and respective signature fragment encoded thereby allows authentication of the entire signature.