Patent ID: 8031051

Claim:
A privacy protection method for preventing an invasion of privacy performed by reading an proper identifier and on the basis of said proper identifier, including: an identifier guard step of bringing an proper identifier of a radio identifier transmitter affixed to an article purchased and thereby possessed by a personal user into an identifier guard state not readable by a stranger according to the intention of said personal user; an identifier generation step of generating an identifier for disturbing a privacy invader with a privacy protection identifier transmitter possessed by said personal user; a transmission step of transmitting said identifier generated through said identifier generation step from said privacy protection identifier transmitter when receiving an identifier transmission request; and a reading step of rendering the identifier of said radio identifier transmitter in the identifier guard state readable according to the intension of the personal user, wherein said identifier generation step includes a variable identifier generation step capable of generating an identifier different from a precedently transmitted identifier; and said transmission step transmits the same identifier as a precedently transmitted identifier when receiving an identifier transmission request again within a prescribed time from precedent identifier transmission.