Authentication device, authentication method, and recording medium

An authentication method comprising:

• storing, in a storage unit, shared information including a password and a shared rule, the password and the shared rule being preset for each user, the shared rule including a shared pattern and a calculation rule that are preset by the user, the shared pattern being a pattern indicating an order of selecting a provisional numeral from a random number sequence pattern in which a plurality of different numerals are arranged in a matrix, the calculation rule being a rule related to calculation using the provisional numeral selected from the random number sequence pattern and a secret numeral constituting the password;
• receiving identification information of a user to be authenticated from an input terminal operated by the user to be authenticated;
• generating the random number sequence pattern including a plurality of different numerals in response to reception of identification information of the user to be authenticated;
• transmitting the generated random number sequence pattern to the input terminal in association with the identification information;
• selecting a plurality of provisional numerals from the random number sequence pattern based on the shared rule;
• generating a key code using the plurality of selected provisional numerals and a plurality of secret numerals constituting the password;
• receiving, from the input terminal, the key code consisting of a numeral selected by the user to be authenticated from the random number sequence pattern based on the shared rule;
• and
• authenticating the user to be authenticated based on the key code received from the input terminal and the key code generated by an own device, wherein
• the storage unit stores the shared pattern including a center numeral as a reference and a pattern for selecting the provisional numeral around the center numeral from the random number sequence pattern based on the center numeral.

A non-transitory recording medium recording a program, when executed by a computer, causing the computer to perform:

• storing, in a storage unit, shared information including a password and a shared rule, the password and the shared rule being preset for each user, the shared rule including a shared pattern and a calculation rule that are preset by the user, the shared pattern being a pattern indicating an order of selecting a provisional numeral from a random number sequence pattern in which a plurality of different numerals are arranged in a matrix, the calculation rule being a rule related to calculation using the provisional numeral selected from the random number sequence pattern and a secret numeral constituting the password;
• receiving identification information of a user to be authenticated from an input terminal operated by the user to be authenticated;
• generating the random number sequence pattern including a plurality of different numerals in response to reception of identification information of the user to be authenticated;
• transmitting the generated random number sequence pattern to the input terminal in association with the identification information;
• selecting a plurality of provisional numerals from the random number sequence pattern based on the shared rule;
• generating a key code using the plurality of selected provisional numerals and a plurality of secret numerals constituting the password;
• receiving, from the input terminal, the key code consisting of a numeral selected by the user to be authenticated from the random number sequence pattern based on the shared rule;
• and
• authenticating the user to be authenticated based on the key code received from the input terminal and the key code generated by an own device, wherein
• the storage unit stores the shared pattern including a center numeral as a reference and a pattern for selecting the provisional numeral around the center numeral from the random number sequence pattern based on the center numeral.