A method of authenticating an object in which a computer system receives indicating data from a sensing device. The indicating data is generated in response to sensing of coded data and is indicative of an identity of the object and a plurality of signature fragments, the signature being a digital signature of at least part of the identity. The computer system uses the indicating data to determine the identity and the plurality of signature fragments. The plurality of signature fragments are then used to determined a determined signature, which is in turn used to generate a generated identity. The identity is then compared to the generated identity to authenticate the object.