Patent ID: 8037294

Claim:
An identification tag for authenticating a product, wherein the identification tag is associated with the product and has authentication data transmissible to a reader device; the authentication data comprising: source data comprising a tag identifier that uniquely identifies the identification tag, a key identifier, and a product identifier that directly identifies a physical property value of the product, wherein the key identifier identifies the public key by specifying an access through the Internet to a database providing the public key, wherein the database is controlled by an authentication authority that maintains public keys for authenticating products, and wherein the physical property value is verifiable by a measurement of the product so that an authentic product is distinguishable from a non-authentic product on the basis of the physical property value; and a signature value being a result of a private key encryption of a representation of the source data, wherein the private key encryption uses a private key of a public key encryption method, wherein the key identifier identifies a public key that is applicable with a public key decryption to decrypt data which have been encrypted with the private key encryption using the private key.