SERVER CAPABLE OF PERFORMING AUTHENTICATION WITH SIMPLIFIED AND SECURE SCHEME THAT USERS WHO OPERATE TERMINALS COMMUNICATING DATA WITH EACH OTHER SATISFY PRESCRIBED RELATION, METHOD OF CONTROLLING SERVER, NON-TRANSITORY STORAGE MEDIUM ENCODED WITH COMPUTER READABLE CONTROL PROGRAM, AND INFORMATION PROCESSING SYSTEM

A server which can communicate with a plurality of terminals includes an information obtaining unit obtaining position information of each terminal and operation information on an operation onto an operation unit provided on a surface of each terminal, a position determination unit determining whether obtained position information of one terminal and position information of at least one other terminal satisfy a first prescribed condition, an operation determination unit determining whether obtained operation information of one terminal and operation information of at least one other terminal satisfy a second prescribed condition, and a registration manager having information on a user of one terminal and information on a user of at least one other terminal registered in correspondence with each other when both of the first prescribed condition and the second prescribed condition are satisfied.