APPARATUS, SYSTEM, AND METHOD FOR DETECTING UNAUTHORIZED CONNECTIONS OF A CHARGE/DISCHARGE DEVICE

An unauthorized connection detecting device (100) which detects an unauthorized charge/discharge device includes: a time information obtaining unit (110) obtaining, as time information, information from a first charge/discharge device (20), the information indicating at least one of an issuing date of a first certificate which is a public key certificate and an issuing date of a certificate revocation list held by the first charge/discharge device (20); an expiration date obtaining unit (120) obtaining expiration date information from a second charge/discharge device (30), the expiration date information indicating an expiration date of a second certificate which is a public key certificate held by the second charge/discharge device (30); and an unauthorization detecting unit (130) detecting whether or not the second charge/discharge device (30) is the unauthorized charge/discharge device by comparing the time information with the expiration date information.