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.