It is made possible to specify a person receiving data in delivering data such as image data. Also, to render it possible to reliably verify a range of received data, specific information is embedded changing an embedding position for each receiver receiving data delivery when data 120, such as image data, voice data and the like, is delivered via a public line network 120. At a receiver side, the above-mentioned specific information is read out by employing information reading means 114 that the embedding position is made known to, and the read information is encrypted and output along with information to specify a receiver.