METHOD OF CREATING SHARED INFORMATION IN COMMUNICATION TERMINAL DEVICE

PROBLEM TO BE SOLVED: To perform radio communication in an ad-hoc mode by easily creating high-security shared information (secret key) in a plurality of communication terminal devices. SOLUTION: Two communication terminal devices are swung multiple times while being held integrally, to produce acceleration data, respectively. Each of the communication terminal devices extracts peak positions Pa1-Pa5 or peak positions Pb1-Pb5 from its acceleration data. Times ta1-ta4 and tb1-tb4 between peak positions are irregular and become information common between two communication terminal devices. Each of the communication terminal devices creates shared information constituted of a plurality of the same bit information from the time between the peak positions. Mutual authentication is performed between two communication terminal devices utilizing the shared information and further encryption is performed. COPYRIGHT: (C)2011,JPO&INPIT