To secure security by ciphering an input data set related to a unique identification number fixed to the surface of unforgeable document, fixing a unique data sign to a unique article and one of approval certificates and authenticating the unique article.

A data set provided with at least one data sub set provided with a first data set for displaying the unique identification number fixed to the surface of the unforgeable document (a currency note provided with a serial number, a cash card for instance) is obtained (S101). The input data set is ciphered by using public and private key ciphering algorithm and the unique data sign is generated (S105). The unique data sign is fixed at least to the unique article and one of the approval certificates (S106) and the unique article is authenticated. Thus, the security is secured.