Patent ID: 8489881

Claim:
A method of transmitting position/time information, comprising: receiving, at a communication apparatus from a communication counterpart, assist information to identify at least one available positioning satellite; receiving, at the communication apparatus, a signal from the at least one positioning satellite identified in the assist information and measuring a reception position and a reception time of said signal; generating, at the communication apparatus, a digital signature of said position/time information, said digital signature based on said signal received from said at least one positioning satellite, and indicating said reception position and said reception time of said signal, the digital signature being generated using a secret key corresponding to identification information of the communication apparatus; attaching the digital signature to the position/time information; transmitting from the communication apparatus to the communication counterpart said position/time information having said digital signature attached thereto; transmitting said identification information of said communication apparatus to said communication counterpart in one of prior, after and at a time of transmission of said position/time information having said digital signature attached thereto; verifying, at the communication counterpart and with a public key corresponding to said communication counterpart, said digital signature attached to said position/time information, the verifying based on said identification information of said communication apparatus; and based on a result of said verification, determining whether said position/time information is legitimate information when the verification step is completed, and determining whether the position/time information has been altered and is illegitimate information when the verification step is not completed; receiving, at the communication apparatus, a selection by a user of condition information; providing services from the communication counterpart to the communication apparatus based on the position/time information, when the position/time information is legitimate; discarding, at the communication counterpart, the position/time information, when the position/time information is illegitimate; confirming that the communication apparatus has met the condition information based on legitimate position/time information; providing special information to the communication apparatus when the communication apparatus has met the condition information; and displaying, by the communication apparatus, position information of the communication counterpart when the communication apparatus is receiving data input by a user of the communication counterpart.