Authentication device, authentication method, and recording medium

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2012-193261, filed on Sep. 3, 2012, the entire contents of which are incorporated herein by reference.

The embodiments discussed herein are related to an authentication device, an authentication method, and a recording medium.

Authentication processing using a password is performed in various devices, such as personal computers, mobile phones, automated teller machines (ATMs) of banks, and various types of integrated computers. In such devices, when a password mismatch has occurred a specified number of times, processing such as password invalidation and stopping authentication during the day of the password mismatch is performed in some cases. This inhibits a malicious third party from discovering a password by trial and error and achieving unauthorized access to a device. Reducing the specified number results in improvement in security level. It is, however, conceivable that a legitimate user repeatedly enters an incorrect password. Therefore, the convenience of a user would be impaired if the specified number is excessively reduced.

There is known a personal information transaction device in which the relationship between each digit and the next digit in a touch panel is stored, and if the number of times a user presses the next digit by mistake is within a permissible range, that number of times is not included in the count of the specified number and the user is allowed to again input a password.

There is also known a password verification device in which if an input password contains an incorrect entry and the incorrect entry matches the immediately previous incorrect entry, the incorrect entry is not counted.

The above personal information transaction device determines on the basis of a key arrangement in an input unit whether an incorrect entry is a mere incorrect entry. It is, therefore, impossible in some cases to sufficiently enhance convenience. This is because characters and digits that are likely to be incorrectly input vary depending on users, and not all the characters and digits located next to each other are likely to be incorrectly input. Also, keys located next to each other include both those that are likely to be incorrectly input and those that are not.

Also, the above password verification device simply does not count an incorrect entry on the basis of the relationship to an incorrect entry made immediately before. This does not sufficiently reflect characters and digits that are likely to be incorrectly input by a user. For this reason, it is impossible in some cases to sufficiently enhance convenience.

Japanese Laid-open Patent Publication No. 9-212723 and Japanese Laid-open Patent Publication No. 2011-59880 disclose examples of the related art.

According to an aspect of the embodiments, an authentication device includes an input unit configured to accept input, an authentication unit configured to determine whether an input password input to the input unit matches a registered password registered in advance in a storage unit, count the number of times it is determined that the input password does not match the registered password, and stops authentication using a password if the number of times a mismatch is determined reaches a specified number, and a management unit configured to create an input error list supporting each of characters, digits, or other elements included in the registered password, on the basis of a history of errors of input to the input unit, and cause the list to be stored in the storage unit, and configured to cancel counting in a case where it is determined by the authentication unit that the input password does not match the registered password and a cause of the mismatch lies in an input error included in the input error list.

The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.

FIG. 1 illustrates an example of a configuration of an authentication device according to a first embodiment;

FIG. 2 is an example of a flowchart illustrating the flow of a process performed by the authentication device;

FIG. 3 is an example of a flowchart illustrating the flow of a password input process performed by the authentication device;

FIG. 4 illustrates an example of data structures of an input data array and an input error temporary management database;

FIG. 5 is an illustration for explaining a pair of input characters registered into the input error temporary management database by execution of the process of the flowchart of FIG. 3 ;

FIG. 6 is an example of a flowchart illustrating the flow of a process of updating the input error management database performed by the authentication device;

FIG. 7 exemplifies data structures of the input error temporary management database and an input error management database;

FIG. 8 is an example of a flowchart illustrating the flow of a process of verification against the input error management database performed by the authentication device;

FIG. 9 is an example of a data structure of a registered password;

FIG. 10 schematically illustrates a manner in which whether the target input error is an “input error not to be counted” or an “input error to be counted” is determined by execution of the process of the flowchart illustrated in FIG. 8 ;

FIG. 11 is another example of the flowchart illustrating the flow of the process of verification against the input error management database performed by the authentication device;

FIG. 12 schematically illustrates a manner in which an input challenge including input of a registered password is presented and an input error is reflected in the input error management database; and

FIG. 13 is an example of a flowchart illustrating the flow of a process of updating the input error management database performed by an authentication device.

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

Embodiments

Hereinafter, an authentication device, an authentication method, and an authentication program will be described with reference to the drawings. The authentication device, authentication method, and authentication program of the present disclosure, which are applicable to various devices, such as personal computers and mobile phones, ATMs of banks, and various types of integrated computers, are assumed to be applied to a personal computer in the below description.

First Embodiment

An authentication device 1 according to a first embodiment will be described below. FIG. 1 illustrates an example of a configuration of the authentication device 1 according to the first embodiment. The authentication device 1 includes a central processing unit (CPU) 10 , a drive device 12 , a storage device 16 , a memory device 18 , a graphics processing device 20 , an input interface 22 , and a communication interface 24 , for example. These components are connected, for example, through a bus.

The CPU 10 is, for example, a processor as an arithmetic processing unit including a program counter, an instruction decoder, various computing units, a load-store unit (LSU), a general register, and so forth.

The drive device 12 is a device capable of reading programs and data from a storage medium 14 . When the storage medium 14 in which programs are recorded is inserted in the drive device 12 , the programs from the storage medium 14 are installed in the storage device 16 through the drive device 12 . The storage medium 14 is, for example, a portable storage medium such as a compact disc (CD), a digital versatile disc (DVD), and a universal serial bus (USB) memory.

The storage device 16 is a hard disk drive (HDD) or a flash memory, for example. Programs such as a password authentication program 16 A and an input error management program 16 B, and data such as an input error management database 16 C and a registered password 16 D are stored in the storage device 16 . Note that the password authentication program 16 A and the input error control program 16 B do not have to be programs that are clearly separate.

In addition to the use of the storage medium 14 as mentioned above, programs may be installed in such a way that the communication interface 24 downloads programs through the network 36 from another computer and installs the programs in the storage device 16 . The network 36 is the Internet, a local area network (LAN), a wireless network, or the like. The programs may be stored in advance in the storage device 16 , a read only memory (ROM), or the like at the time of shipment of the authentication device 1 .

The programs installed or stored in advance in such a way, when executed by the CPU 10 , cause an information processing device in the form illustrated in FIG. 1 to be able to function as the authentication device 1 of this embodiment.

The memory device 18 is a random access memory (RAM) or an electrically erasable and programmable read only memory (EEPROM), for example. Data such as an input data array 18 A and an input error temporary management database 18 B are stored in the memory device 18 .

The graphics processing device 20 is connected to a display device 30 and generates a screen to be displayed by the display device 30 . A keyboard 32 , a mouse 34 , and other input devices are connected to the input interface 22 .

Here, in the case where the authentication device 1 is connected to a device other than a personal computer, the input interface 22 is connected to ten keys, a touch panel (some personal computers are provided with touch panels), and other input devices.

The authentication device 1 includes a password authentication unit 10 A and an input error management unit 10 B as functional blocks that function when the CPU 10 executes programs stored in the storage device 16 . It is unnecessary for these functional blocks to be implemented by clearly separated programs. The functional blocks may be subroutines or functions that are called by other programs. It is also acceptable that some of the functional blocks are hardware units such as a large scale integrated (LSI) circuit, an integrated circuit (IC), and a field programmable gate array (FPGA).

The password authentication unit 10 A is activated, for example, upon logging into the authentication device 1 , and determines whether a password input (hereinafter referred to as an “input password”) by using the keyboard 32 and the input interface 22 matches a password registered in advance (hereinafter referred to as a “registered password”) in the storage device 16 . Then, the password authentication unit 10 A counts the number of times it is determined that the input password does not match the registered password, and stops the authentication using a password when the number of times it is determined that the passwords do not match reaches a specified number T.

The input error management unit 10 B creates and updates an input error management database 16 C on the basis of a history of a user's input to the keyboard 32 and the input interface 22 . If it is determined by the password authentication unit 10 A that an input password and the registered password do not match, and the cause of the mismatch lies in an input error registered in the input error management database 16 C, the input error management unit 10 B cancels counting of the input for which the above negative determination is made.

The contents of processes of the password authentication unit 10 A and the input error management unit 10 B will be described hereinafter with reference to flowcharts.

FIG. 2 is an example of a flowchart illustrating the flow of a process performed by the authentication device 1 . The process of the flowchart of FIG. 2 is performed, for example, when the authentication device 1 is activated and a user is going to log in. Note that the order in which the process is performed in each of the flowcharts illustrated below may be changed to any order as long as the same processing result is obtained.

First, the authentication device 1 reads the value T for counting a specified number of mismatch determinations from the storage device 16 , a ROM, or the like (S 100 ). The value T is a positive integer.

Then, the authentication device 1 performs a password input process (S 102 ; refer to FIG. 3 ).

FIG. 3 is an example of a flowchart illustrating the flow of the password input process performed by the authentication device 1 .

First, the authentication device 1 sets the number of characters (or digits) n to zero and BS_Flg to OFF, as the initial setting (S 200 ). The number of characters n is a value indicating what number character the current character is in a password, and BS_Flg is a flag indicating that a BS key, that is, a backspace key has just been pressed. These data are stored in the memory device 18 , for example. The length of the registered password is stored in the storage device 16 as a value N.

Then, the authentication device 1 waits until input to the keyboard 32 is made (S 202 ).

Upon input to the keyboard 32 , the authentication device 1 stores an input character M in the memory device 18 , for example, and increments the number of characters n by one (S 204 ). Hereinafter, the term “character” will include both characters in a narrow sense and digits.

Then, the authentication device 1 determines whether the input character M is a character input using the Enter key (S 206 ).

If the input character M is not a character input using the Enter key, then the authentication device 1 determines whether the input character M is a character input using the BS key, that is, the backspace key (S 208 ).

If the input character M is neither a character input using the Enter key nor a character input using the backspace key, that is, if an ordinary character input is made, the authentication device 1 determines whether BS_Flg is ON (S 210 ). If BS_Flg is OFF, the authentication device 1 stores the input character M in the n-th cell (m, n) of the input data array 18 A [(m, n); n=one to N] (S 212 ). FIG. 4 illustrates an example of data structures of the input data array 18 A and the input error temporary management database 18 B. If BS_Flg is ON, that is, if the previous input is made using the backspace key, the authentication device 1 copies the n-th cell (m, n) of the input data array 18 A into the n-th cell (p, n) of the input error temporary management database 18 B. The authentication device 1 stores the input character M in the n-th cell (m, n) of the input data array 18 A (S 214 ). Then, the authentication device 1 changes BS_Flg to OFF (S 216 ), and returns to S 202 .

If the input character M is a character input using the backspace key, the authentication device 1 determines whether the number of characters is one (S 218 ). If the number of characters n is not one, the authentication device 1 decrements the number of characters n by two and changes BS_Flg to ON (S 220 ), and returns to S 202 . If the number of characters n is one, the authentication device 1 returns the number of characters n to zero (S 222 ), and returns to S 202 .

If the input character M is a character input using the Enter key, the authentication device 1 determines that an operation of determining the input password has been performed, and causes the content of the input error temporary management database 18 B to be reflected in the input error management database 16 C (S 224 ; refer to FIG. 6 ). That is, the authentication device 1 performs a process of updating the input error management database 16 C, and completes the process of the flowchart of FIG. 3 .

FIG. 5 is an illustration for explaining a pair of input characters registered into the input error temporary management database 18 B by execution of the process of the flowchart of FIG. 3 . As illustrated in FIG. 5 , when a user inputs characters in the order A→B→C→X→BS (backspace)→D→E, it is inferred that the fourth character X is an error and the right character is D. In this case, in the input error temporary management database 18 B, the right input character D is stored in cell (m, 4), and the erroneously input character X is stored in cell (p, 4).

FIG. 6 is an example of a flowchart illustrating the flow of the process of updating the input error management database 16 C performed by the authentication device 1 . The process of the flowchart of FIG. 6 is executed by the input error management unit 10 B. Also, FIG. 7 exemplifies the data structures of the input error temporary management database 18 B and the input error management database 16 C. In the input error management database 16 C, the correct character (0, n, s) and the past erroneously input characters (a, n, s) are stored in association with each other for each character number n of the registered password. The parameter a is a value indicating that the smaller the value, the larger the number of occurrences of an input error. The past erroneously input characters are sorted based on the respective numbers of occurrences of an input error (a, n, d) in such a way that the larger the number of occurrences of an input error, the higher (a is smaller) the erroneously input character is ranked.

As the process of the flowchart illustrated in FIG. 6 begins, the authentication device 1 sets the number of characters n to one and the parameter a to one, as the initial setting (S 300 ).

Then, the authentication device 1 determines whether data exists in cell (p, n) in the input error temporary management database 18 B (S 302 ).

If data exists in cell (p, n) in the input error temporary management database 18 B, the authentication device 1 determines whether cell (p, n) matches cell (a, n, s) in the input error management database 16 C (S 304 ). If cell (p, n) matches cell (a, n, s), the authentication device 1 increments the number of occurrences of an input error (a, n, d) by one (S 306 ).

If cell (p, n) does not match cell (a, n, s), the authentication device 1 determines whether data exists in cell (a, n, s) (S 308 ). If data does not exist in cell (a, n, s), the authentication device 1 newly adds the character of cell (p, n) to cell (a, n, s), and sets the number of occurrences of an input error (a, n, d) to one (S 310 ). If data exists in cell (a, n, s), the authentication device 1 increments the parameter a by one (S 312 ), and returns to S 304 .

In S 302 , if it is determined that data does not exist in cell (p, n), or after the operation of S 306 or S 308 , the authentication device 1 determines whether the number of characters n matches the length N of the registered password (S 314 ).

If the number of characters n does not match the length N of the registered password, the authentication device 1 returns to S 302 . Otherwise, the number of characters n matches the length N of the registered password, the authentication device 1 vertically sorts the characters (a, n, s) of character numbers in such a way that the larger the number of occurrences of an input error (a, n, d), the higher (a is smaller) the character (a, n, s) is ranked (S 318 ), and completes the process of the flowchart of FIG. 6 .

With reference back to FIG. 2 , the description of the flow of the entire process will be continued. Upon completion of the password input process described with reference to FIG. 3 and FIG. 6 , the authentication device 1 determines whether the input password matches the registered password (S 104 ). If the input password matches the registered password, the authentication device 1 performs login processing (S 106 ), and completes the process of the flowchart of FIG. 2 . After the login processing, application programs and so forth a user desires to use are available.

Otherwise, if the input password does not match the registered password, the authentication device 1 performs a process of verification against the input error management database 16 C (S 108 ; refer to FIG. 8 ).

FIG. 8 is an example of a flowchart illustrating the flow of the process of verification against the input error management database 16 C performed by the authentication device 1 . The process of the flowchart of FIG. 8 is executed by the input error management unit 10 B. Also, FIG. 9 is an example of a data structure of a registered password 16 D. The registered password 16 D has a data structure that supports every character indicated by the number of characters n and in which a correct character (t, n) is stored, for example.

As the process of the flowchart of FIG. 8 begins, the authentication device 1 sets the number of characters n to one and the parameter a to one, as the initial setting (S 400 ).

Then, the authentication device 1 determines whether the n-th character (m, n) of the input password matches the n-th character (t, n) of the registered password (S 402 ).

If the n-th character (m, n) of the input password matches the n-th character (t, n) of the registered password, the authentication device 1 determines whether the number of characters n matches the value N (S 404 ). If the number of characters n does not match the value N, the authentication device 1 increments the number of characters n by one, and sets the parameter a to one (S 406 ), and returns to S 402 .

If the n-th character (m, n) of the input password does not match the n-th character (t, n) of the registered password, the authentication device 1 determines whether data exists in cell (a, n, s) (S 408 ).

If data exists in cell (a, n, s), the authentication device 1 determines whether the n-th character (m, n) of the input password matches a character stored in cell (a, n, s) of the input error management database 16 C (S 410 ). If the character (m, n) matches the character in cell (a, n, s), the authentication device 1 increments the number of occurrences of an input error (a, n, d) of the target character by one (S 412 ), and proceeds to S 404 .

If the character (m, n) does not match the character in cell (a, n, s), the authentication device 1 increments the parameter a by one, and returns to S 408 .

If it is determined in S 404 that the number of characters n matches the value N, the authentication device 1 vertically sorts the characters (a, n, s) of character numbers in such a way that the larger the number of occurrences of an input error (a, n, d), the higher (a is smaller) the character (a, n, s) is ranked (S 416 ). Then, the authentication device 1 determines that the target input error is an “input error not to be counted” the number of which is not included in the specified number of mismatches to be counted (S 418 ), and completes the process of the flowchart of FIG. 8 . The operation of S 416 and the operation of S 418 are performed when all the characters (m, n) of the input password match the corresponding characters (t, n) of the registered password or characters (a, n, s) stored in the input error management database 16 C.

Otherwise, it is determined in S 408 that data does not exist in cell (a, n, s), the authentication device 1 determines that the target input error is an “input error to be counted” the number of which is included in the specified number of mismatch determinations (S 420 ), and completes the process of the flowchart of FIG. 8 . The operation of S 420 is performed when any character (m, n) of the input password matches neither the corresponding character (t, n) of the registered password nor the character stored in the character (a, n, s) stored in the input error management database 16 C.

FIG. 10 schematically illustrates a manner in which whether the target input error is an “input error not to be counted” or an “input error to be counted” is determined by execution of the process of the flowchart illustrated in FIG. 8 . As illustrated in FIG. 10 , when the character of each character number matches the corresponding character (t, n) of the registered password or the character (a, n, s) stored in the input error management database 16 C, the target input error is determined as an “input error not to be counted”.

With reference back to FIG. 2 , the description of the flow of the entire process will be continued. Upon completion of the process of verification against the input error management database 16 C described with reference to FIG. 8 , the authentication device 1 determines whether a determination result of an “input error not to be counted” has been obtained (S 110 ). If the determination result of the “input error not to be counted” has been obtained, the authentication device 1 returns to S 102 , and performs again the password input process.

Otherwise, if a determination result of an “input error to be counted” has been obtained, the authentication device 1 decrements the value T by one (S 112 ), and then determines whether the value T has become zero (S 114 ). If the value T has not become zero, the authentication device 1 returns to S 102 , and performs again the password input process. If the value T has become zero, the authentication device 1 does not permit login. In this case, the authentication device 1 invalidates the password and performs processing that requests a user to reset a password in a predetermined procedure, for example.

Note that the operations of S 104 , S 106 , S 112 , S 114 , and S 116 in the flowchart of FIG. 2 are executed by the password authentication unit 10 A, for example, and the operations of other steps are executed by the input error management unit 10 B, for example.

As a result of the processes described above, information on characters that are likely to be erroneously input by a user is stored in the input error management database 16 C. Then, if only erroneously input characters that are the same as the characters stored in the input error management database 16 C are included in a password input by the user, the counting of the specified number of mismatches will be canceled. Thereby, when a user makes an input error for a character that is likely to be erroneously input by the user, it is possible for the user to repeatedly reenter the character. This improves convenience. On the other hand, it is difficult for a malicious third party to infer a character that is likely to be erroneously input by a legitimate user. Therefore, even if counting of the number of times it is determined that passwords do not match is in part cancelled, the reduction in security level is small. Accordingly, the authentication device 1 of this embodiment may improve convenience while maintaining the security level.

Also, the authentication device 1 of this embodiment creates and updates the input error management database 16 C as a list of input errors for each of the characters or digits constituting the registered password. Therefore, the input error management database 16 C is a database in which the characters or digits that are likely to be erroneously input by a user are sufficiently reflected. As a result, the authentication device 1 of this embodiment may further improve convenience.

Also, the input error corrected by using the backspace key is reflected in the input error management database 16 C. Therefore, when a certain input error is made for the first time at the determination stage of password input, the input error is in some cases not included in the specified number of mismatches to be counted. Such a scene occurs, for example, in the case where after a certain input error is made, the error is corrected by using the backspace key, and, at the time of login made several times later, the same input error is detected at the determination stage. In this scene, if the input error management database 16 C was created and updated only on the basis of a comparison between a temporarily determined input password and the registered password, the first input error would be included in the specified number of mismatches to be counted. In contrast to this, the authentication device 1 of this embodiment causes the input error corrected by using the backspace key to be reflected in the input error management database 16 C. Therefore, even with the first input error at the determination stage, the count of the specified number of mismatches is canceled in some cases. As a result, the authentication device 1 of this embodiment may further improve convenience.

With the authentication device 1 of this embodiment described above, convenience may be improved for a user.

Note that the authentication device 1 of the first embodiment may cause corrected input errors to be reflected in the input error management database 16 C, for example, in the case where correction by using the <←>+<Delete> keys is made as well as in the case where correction by using the backspace key is made.

Also, the authentication device 1 of the first embodiment may determine whether the target input error is an “input error not to be counted” for not all the input errors stored in the input error management database 16 C but a limited number of those having a higher number of occurrences. In this case, the process of the flowchart of FIG. 11 , for example, is executed instead of the process of the flowchart of FIG. 8 .

FIG. 11 is another example of the flowchart illustrating the flow of the process of verification against the input error management database 16 C performed by the authentication device 1 . Here, only differences (S 414 _ 1 to S 414 _ 2 ) from the flowchart of FIG. 8 will be described.

If it is determined in S 410 that the character (m, n) does not match the character in cell (a, n, s), the authentication device 1 determines whether the parameter a is equal to or less than a reference value (about two, for example) (S 414 _ 1 ). If the parameter a is equal to or less than the reference value, the authentication device 1 increments the parameter a by one (S 414 _ 2 ), and returns to S 408 . Otherwise, if the parameter a exceeds the reference value, the authentication device 1 determines the target input error is an “input error to be counted” (S 420 ), and completes the process of the flowchart of FIG. 11 .

Thus, the authentication device 1 determines the target input error to be an “input error not to be counted” if the target input error is an input error the number of occurrences of which is ranked from top to the (reference value+1)-th, and determines the target input error to be an “input error to be counted” if the target input error is an input error the number of occurrences of which is ranked low. As a result, as compared with the case where the process of the flowchart illustrated in FIG. 8 is executed, the security level improves and a user is put at a slight disadvantage in terms of the counting of the specified number of mismatches.

Second Embodiment

Hereinafter, an authentication device 2 according to a second embodiment will be described. The authentication device 2 according to the second embodiment has a configuration in common with the first embodiment, and therefore elements will be denoted by the same reference characters and will be described.

An input error management unit 10 B according to the second embodiment presents in advance a character input challenge to a user, and creates and updates the input error management database 16 C on the basis of an input error that occurs when a user makes input in order to address the challenge. This challenge includes inputting characters that form the registered password. Note that the authentication device 2 according to the second embodiment, as in the first embodiment, may cause an input error occurring in an event of actual password input to be reflected in the input error management database 16 C. Accordingly, the same processing as in the first embodiment may be performed for processes other than the process of updating the input error management database 16 C.

FIG. 12 schematically illustrates a manner in which an input challenge including input of a registered password is presented and an input error is reflected in the input error management database 16 C.

FIG. 13 is an example of a flowchart illustrating the flow of a process of updating the input error management database 16 C performed by the authentication device 2 . The process of the flowchart of FIG. 13 may begin at an arbitrary timing, and may be performed repeatedly, not only once.

First, the authentication device 2 generates a random input challenge including input of a password, and presents the challenge to a user by using the display device 30 or the like (S 500 ).

Then, the authentication device 2 waits until the user completes inputting characters the number of which is included in the input challenge (S 502 ). Upon completion of the input, the authentication device 2 extracts characters the number of which correspond to the number of characters of a password included in the input challenge, from a character string input by the user, and stores the characters as the input data array 18 A [(m, n); n=one to N], as in the first embodiment, in the memory device 18 , for example (S 504 ).

Then, the authentication device 2 sets the number of characters n to one, and the parameter a to one as the initial setting (S 506 ).

Then, the authentication device 2 determines whether the n-th character (m, n) of the input password matches the n-th character (t, n) of the registered password (S 508 ).

If the n-th character (m, n) of the input password matches the n-th character (t, n) of the registered password, the authentication device 2 determines whether the number of characters n matches the value N (S 510 ). If the number of characters n does not match the value N, the authentication device 2 increments the number of characters n by one and set the parameter a to one (S 512 ), and returns to S 508 .

If the n-th character (m, n) of the input password does not match the n-th character (t, n) of the registered password, the authentication device 2 determines whether cell (p, n) matches cell (a, n, s) in the input error management database 16 C (S 514 ). If cell (p, n) matches cell (a, n, s), the authentication device 2 increments the number of occurrences of an input error (a, n, d) by one (S 516 ), and proceeds to S 510 .

If cell (p, n) does not match cell (a, n, s), the authentication device 2 determines whether data exists in cell (a, n, s). If data does not exists in cell (a, n, s), the authentication device 2 newly adds the character of cell (p, n) into cell (a, n, s), and sets the number of occurrences of an input error (a, n, d) to one (S 520 ). If data exists in cell (a, n, s), the authentication device 2 increments the parameter a by one (S 522 ), and returns to S 514 .

It is determined in S 510 that the number of characters n matches the length N of the registered password, the authentication device 2 vertically sorts the characters (a, n, s) of character numbers in such a way that the larger the number of occurrences of an input error (a, n, d), the higher (a is smaller) the character (a, n, s) is ranked (S 524 ), and completes the process of the flowchart of FIG. 13 .

The authentication device 2 of this embodiment described above, as in the first embodiment, it is possible to improve convenience while maintaining the security level.

Also, the input error management database 16 C is created and updated on the basis of a result obtained by presenting an input challenge in advance and making input. Therefore, even with the first input error at the determination stage of password input, counting of the specified number of mismatches is not made in some cases. As a result, the authentication device 2 of this embodiment may further improve convenience.

Note that, in the first and second embodiments, the input interface 22 , the keyboard 32 , and the mouse 34 , or some of these components are included in examples of the “input unit”. Also, the password authentication unit 10 A is included in examples of the “authentication unit”, and the input error management unit 10 B is included in examples of the “management unit”.

As described above, although the forms for carrying out the present disclosure have been described using the embodiments, the present disclosure is not limited to such embodiments at all, and various modifications and replacements may be made without departing from the scope of the present disclosure.

All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.