The present invention relates to an authentication device and an authentication method of executing authentication based on an image, and a non-transitory computer-readable recording medium.
In recent years, there has been increasing progress in the high-functionality and multi-functionality functions of portable devices such as a portable telephone, a mobile computer, a portable game device, and a music reproducing device. Following the progress in such high-functionalization and multi-functionalization functions, a security measure for preventing improper use of a portable device has become important.
For a security measure, a face recognition technique of using a camera which is becoming a standard installation in a portable device is the focus of attention. Personal authentication (face authentication) to which the face recognition technique is applied can confirm an owner by photographing a face from among natural movements, and is, therefore, valid as a security measure which is also highly convenient.
On the other hand, as a task of a face recognition technique, there is a countermeasure against “impersonation” that uses a photograph or the like. The “impersonation” is a behavior that a person other than an eligible person attempts to receive authentication by using a photograph or the like of the eligible person. Particularly, recent portable devices include a megapixel-class camera and have a focus function and a close-up photography function. Therefore, there is a risk that impersonation can be easily done by using a snap photograph or a small photograph such as a photograph for a driving license.
Therefore, techniques of preventing impersonation are being developed. For example, Japanese Patent Publication No. 3562970 discloses a technique of preventing impersonation by deciding whether a visual line of a user is directed to a light source that guides the visual line of the user. Further, Japanese Patent Publication No. 4470663 discloses a technique of preventing impersonation by deciding whether a visual line movement of a user coincides with a track of a mark displayed on a display by moving the mark at random. Japanese Patent Publication No. 4807167 discloses a technique of preventing impersonation by deciding whether a visual line of a user is directed to a display unit. Japanese Unexamined Patent Publication No. 2004-220376 discloses a technique of executing an authentication process by deciding whether a track of a pointer indicating a visual line direction of a user coincides with a predetermined movement pattern, by displaying the pointer and moving the pointer according to an iris position of the user. Further, Japanese Unexamined Patent Publication No. 2005-149326 discloses a technique of executing authentication by deciding whether an image that a user gazes at is a registered image, by detecting a visual line of the user.
However, in conventional techniques as described above, since input candidates (a type of a visual line direction, a guidance mark, an image as a selection alternative, and the like that can be input) are displayed at the time of impersonation prevention decision, another person may easily know the authentication method. Therefore, the conventional techniques have a problem in that there is a case that the impersonation prevention decision for preventing improper authentication does not validly function.