Patent ID: 6747546
Filing Date: 2004-06-08
Classification: G06Q,G07F,H04L

Abstract:
A transponder for data communication, comprising:a plurality of storage areas for storing data used when the transponder communicates individually with a plurality of interrogators managed by different managing parties, the storage areas corresponding one-to-one to the different managing parties; a plurality of storage-area-specific key signals, unique to the transponder and stored so as to correspond one-to-one to the storage areas, for permitting use of only a particular storage area corresponding to an interrogator with which the transponder is currently communicating; a device-specific key signal for distinguishing the transponder from another transponder; an authentication circuit for checking whether the interrogator is authentic or not on a basis of a first authentication signal that is generated in the interrogator by performing a calculation operation according to a first calculation formula on a second authentication signal included in a response signal transmitted from the transponder, which is added to a command signal transmitted from the interrogator; and a calculation circuit for generating, by performing a calculation operation according to a second calculation formula on the first authentication signal, a second authentication signal with which to request the interrogator to authenticate the transponder, wherein, when the transponder receives the command signal from the interrogator, if the first authentication signal included in the command signal is not one generated on a basis of the second authentication signal included in the response signal from the transponder, the transponder, in the authentication circuit, does not authenticate the interrogator, but in the calculation circuit, generates the second authentication signal from the first authentication signal according to the second calculation formula, and transmits to the interrogator the response signal including the second authentication signal and the device-specific key signal, and if the first authentication signal included in the command signal is one generated on a basis of the second authentication signal included in the response signal from the transponder, the transponder, in the authentication circuit, authenticates the interrogator, and checks whether or not the storage-area-specific key signal included in the command signal coincides with the storage-area-specific key signal stored so as to correspond to a specific storage area allocated to the managing party that manages the interrogator so that, if the two storage-area-specific key signals coincide with each other, the transponder becomes communicable with the interrogator by using only that specific storage area.