1. An information processing device which performs personal authentication based on a video signal obtained through imaging of an object person, comprising: imaging means for performing imaging of one of the object person and a registrant to generate the video signal; first feature amount calculation means for calculating a feature amount of a face of the registrant in an image of the video signal obtained through imaging of the registrant in a registration mode; second feature amount calculation means for calculating time series of feature amount of a lip of the registrant in an image of the video signal obtained through imaging of the registrant speaking an arbitrary password in the registration mode; registration means for registering the calculated time series of feature amount of the lip when the arbitrary password is spoken in a database to be associated with the calculated feature amount of the face of the registrant; identification means for calculating a feature amount of a face in an image of the video signal obtained through imaging of the object person, referencing the database, and identifying the face of the object person in an authentication mode; recognition means for calculating time series of feature amount of a lip of the object person in an image of the video signal obtained through imaging of the object person while speaking, referencing the database, and recognizing speech content of the object person in the authentication mode; and authentication means for performing personal authentication of the object person based on an identification result of the face of the object person and a recognition result of the speech content of the object person.