1. A system for authenticating an object, the system comprising: a sensing device for sensing coded tags printed on the object, each coded tags encoding an identity of the object and a signature fragment, an entire signature being encoded in a plurality of coded tags; a processor for determining a signature fragment identifier associated with respective signature fragments, for generating the entire signature from the signature fragments and associated signature fragment identifiers, for decrypting the entire signature to obtain a generated identity; means for comparing the identity encoded by the coded tags with the generated identity; and means for authenticating the object using the results of the comparison.