1. A method of authenticating an object, the method including, in a computer system: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing of coded data provided on or in a surface associated with the object, the indicating data being indicative of: an identity of the object; a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the indicating data, the identity and the plurality of signature fragments; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.