An information processor includes a read information obtaining unit, a conversion unit, an authentication information obtaining unit, and a conversion method setting unit. The read information obtaining unit obtains read information read from an authentication medium by a reading device. The conversion unit converts the read information in accordance with a predetermined conversion method. The authentication information obtaining unit obtains comparative-purpose authentication information to be used for a comparison with the converted read information. The conversion method setting unit sets, when the converted read information and the comparative-purpose authentication information match each other, the conversion method as a particular conversion method used to convert the read information read by the reading device.