A method of authenticating product packaging is disclosed. The packaging has disposed thereon coded data portions. Each coded data portion is indicative of an identity of the packaging and a part of a digital signature of at least a part of the identity of the packaging. The digital signature comprises a plurality of signature parts. The method starts by receiving indicating data from a sensing device. The sensing device is responsive to sensing one of the coded data portions to generate the indicating data which is indicative of the identity of the packaging, the part of the signature, and a signature part identifier. A determined signature is determined using the identity of the packaging. A determined signature part is determined using the determined signature and the signature part identifier. The packaging is authenticated by comparing the determined signature part and the part of the signature.