1. A method of authenticating an object using a processor, the method including, in the processor: receiving 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; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; determining from the indicating data, a received identity and at least one received signature part; determining, using the received identity and a secret key, a determined signature; comparing the determined signature to the at least one received signature part; and, authenticating the object using the results of the comparison.