Patent ID: 7653946

Claim:
A method for securing circulation of an encrypted digital document to be reproduced with a document reader, the method comprising: providing a user with a storage device storing identification information identifying the storage device and for storing an identification information list comprising identification information identifying recent document readers previously operated with the storage device; transmitting to a server over the digital data transmission network from the storage device to the server upon connection of the storage device to the server by a terminal connected to the digital data transmission network and to the storage device information identifying the digital document to be reproduced, and the information list and the identification information of the storage device; identifying from the server the storage device on the basis of the information identification of the storage device transmitted to the server; determining possible fraudulent use of the storage device based upon the information list that is transmitted to the server, the server comparing the identification information in the information list with an authorized or fraudulent reader list for determining fraudulent use of the storage device; if the storage device is not being fraudulently used, then transmitting over the digital data transmission network from the server to the computer terminal a decryption key specific to the digital document to be reproduced, with the decryption key being stored in the storage device; decrypting the digital document using the stored decryption key by the document reader connected to the storage device; and reproducing the digital document decrypted by the document reader; and if the storage device is being fraudulently used, then the decryption key is not transmitted over the digital data transmission network from the server to the storage device.