JP2018180911A - Authentication device, authentication program, and authentication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent authentication by a password of an attacker without blocking authentication by a password of an authorized user.SOLUTION: An authentication device includes: a counting unit that counts, when storing a newly failed password or corresponding value of the password in a storage unit for storing a predetermined number of passwords or corresponding values of the passwords failed in authentication processing before accepting each correct password, a number of passwords or corresponding values of the passwords to be lost from the storage unit; and an authentication unit that resets, when the counted value is equal to or more than the predetermined number, the counted value without determining that the authentication process is successful when accepting input of a correct password.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an authentication device, an authentication program, and an authentication method.

  In the authentication method based on the combination of two strings of username and password, if a malicious attacker inputs all string patterns in a round-robin manner, authentication will always succeed even if it takes a huge amount of time. There is a problem that you

  Therefore, this technology analyzes the input password to determine whether it is a brute force attack by an attacker, and makes the attacker log in to a fake server after having made several unauthorized password attempts. Has been proposed (see, for example, Patent Document 1). In Patent Document 1, it is determined whether or not a brute force attack is performed by counting the number of times when login fails due to the input of an incorrect password. At this time, when a legitimate user erroneously inputs a password that is likely to be mistaken, processing is performed in which the number of unsuccessful login attempts is not counted.

JP 2001-282739 A JP 2011-59880 A

  However, in the above method, a password that is easy to be mistaken is previously defined, for example, the next key, upper case, and lower case. Therefore, incorrect input of a password other than the error of the predefined password is not considered to be an act of a legitimate user, is determined to be an act of a malicious attacker, and is counted as the number of unsuccessful login attempts. Therefore, in the above method, authentication by the password of a legitimate user may be hindered.

  Therefore, in one aspect, it is an object of the present invention to prevent authentication by an attacker's password without disturbing authentication by an authorized user's password.

  In one embodiment, a password for which authentication processing has failed anew or a corresponding value of the password is stored in a storage unit that stores a predetermined number of passwords for which authentication processing has failed before receiving a correct password or the corresponding value of the password. In the case where the password is lost from the storage unit or the counting unit for counting the number of corresponding values of the password, and when the counted value is equal to or more than the predetermined number, the authentication processing is successful when the input of the correct password is accepted. There is provided an authentication device including: an authentication unit that resets the counted value without determining that it is.

  In one aspect, the present invention can prevent authentication by an attacker's password without inhibiting authentication by a legitimate user's password.

The figure which shows an example of a structure of the authentication system which concerns on one Embodiment, and a function structure of an authentication server. The figure which shows the other example of a function structure of the authentication apparatus (terminal device) which concerns on one Embodiment. The figure which shows an example of the hardware constitutions of the authentication server which concerns on one Embodiment. 5 is a flowchart illustrating an example of an initialization process according to an embodiment. FIG. 6 is a view showing an example of the state of a storage unit at the time of initialization processing according to an embodiment. The flowchart which shows an example of the authentication process which concerns on one Embodiment. The flowchart which shows an example of the authentication process (continuation) which concerns on one Embodiment. FIG. 7 is a view showing an example of the state of a password history storage unit at the time of authentication processing according to an embodiment. The figure which shows an example of the state of the appearance frequency memory | storage part at the time of the authentication process which concerns on one Embodiment. The flowchart which shows an example of the attack determination processing which concerns on one Embodiment. The figure which shows an example of the state of the password log | history memory | storage part at the time of the attack determination which concerns on one Embodiment, and an appearance frequency memory | storage part. The figure which shows an example of the state of the appearance frequency memory | storage part at the time of the attack determination which concerns on one Embodiment. The figure which shows an example of a function structure of the authentication server which concerns on the modification of one Embodiment. The figure which shows an example of the state of the appearance frequency memory | storage part which concerns on the modification of one Embodiment, and the appearance frequency share memory | storage part. The figure which shows an example of the state of the appearance frequency memory | storage part which concerns on the modification of one Embodiment, and the appearance frequency share memory | storage part. The flowchart which shows an example of the attack determination processing which concerns on the modification of one Embodiment. The figure which shows an example of the state of the appearance frequency memory | storage part at the time of the attack determination which concerns on the modification of one Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. In the present specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals and redundant description will be omitted.

[Functional configuration of authentication device]
First, an example of a configuration of an authentication system 1 according to an embodiment of the present invention and a functional configuration of an authentication server 10 will be described with reference to FIG. FIG. 1 shows an example of the configuration of an authentication system 1 and the functional configuration of an authentication server 10 according to an embodiment.

  The authentication system 1 according to the present embodiment includes an authentication server 10 and a terminal device 20. The authentication server 10 and the terminal device 20 are connected via the network 30. The network 30 may be a network such as a public network or a LAN (Local Area Network).

  The authentication server 10 acquires the username and password input from the login screen of the terminal device 20 via the network 30, and determines whether or not the correct username and password have been input. If the authentication server 10 determines that the correct username and password have been input, the authentication server 10 notifies the terminal device 20 of the success of the authentication process, and permits the terminal device 20 to log in. The authentication server 10 is an example of an authentication device, and can be configured by an electronic device having an authentication function and a communication function. The authentication server 10 may be a server on the cloud.

  The terminal device 20 may be a wearable device such as a PC (Personal Computer), a tablet terminal, a smartphone, a PDA (Personal Digital Assistants), a mobile phone, an HMD (Head Mount Display), and an FMD (Face Mount Display).

  The authentication function of the authentication server 10 may be provided inside the terminal device 20. In this case, as shown in FIG. 2, the terminal device 20 has the same authentication function as the authentication server 10 of FIG. The terminal device 20 of FIG. 2 is also an example of an authentication device that determines whether the directly input user name and password are correct and, if correct, permits the user to log in.

  Hereinafter, in the present embodiment, the authentication function and operation of the authentication server 10 of FIG. 1 will be described, and the description of the authentication function and operation of the terminal device 20 of FIG. 2 having the same function will be omitted.

[Function configuration]
An example of a functional configuration of the authentication server 10 according to an embodiment will be described. The authentication server 10 according to the present embodiment includes an input reception unit 11, an input check unit 12, a storage unit 13, a password conversion unit 14, a count unit 15, an authentication unit 16, and a control unit 17.

  The input accepting unit 11 accepts a user name and a password from the terminal device 20 via the network 30. The input check unit 12 determines whether the accepted user name exists and whether the password is correct.

  The password conversion unit 14 converts the input password character string into a numerical value in the range of the size of the storage area of the appearance frequency storage unit 132 using a hash function or the like. The password conversion unit 14 may convert the input password into a value other than the hash value. As an example of the hash function, there is MD5 (MD Five, Message Digest Algorithm 5) that outputs a 128-bit hash value for a given input.

  The authentication unit 16 performs an authentication process based on the received user name and password. Among the user name character string and password character string 135 for each user stored in the storage unit 13, the authentication unit 16 and the user name character string and password character string 135 of the user specified from the serial number of the terminal device and the like , Compare the accepted username and password. The username string and the password string 135 are registered in advance for each user.

  If it is determined that the user name and the password match as a result of the comparison, the authentication unit 16 determines that the authentication is successful, and if it determines that the user name and the password do not match, it determines that the authentication fails. However, while a brute force attack is determined, even if the correct password is input, it is not determined that the authentication is successful once.

  The storage unit 13 has a storage area for each user. For example, the user A storage unit 13a includes a password history storage unit 131a for the user A, an appearance frequency storage unit 132a, an operation mode flag 133a, and an authentication status flag 134a. Similarly, the user B storage unit 13 b and the user C storage unit 13 c also have the above two storage units and two flags.

  Hereinafter, all storage units provided for each user, including the storage unit for user A 13a, the storage unit for user B 13b, and the storage unit for user C 13c, are collectively referred to as the storage unit 13. The password history storage units 131a, 131b,... Are collectively referred to as a password history storage unit 131. The appearance frequency storage units 132a, 132b,... Are collectively referred to as an appearance frequency storage unit 132. The operation mode flags 133a, 133b,... Are collectively referred to as operation mode flags 133. Further, the authentication status flags 134a, 134b,... Are collectively referred to as an authentication status flag 134. That is, the password history storage unit 131, the appearance frequency storage unit 132, the operation mode flag 133, and the authentication state flag 134 are secured independently for each user. The number of users for which the storage location of each information is secured is not limited to three of the user A, the user B, and the user C, and may be one or two or more.

  The password history storage unit 131 stores a hash value obtained by hashing a predetermined number of latest password strings input by the user. Although FIG. 1 describes the number of hash value histories obtained by hashing the password character string as four, it is not particularly limited to four.

  The appearance frequency storage unit 132 stores, for each hash value of the input password, information indicating the presence or absence of the input. In the present embodiment, the appearance frequency storage unit 132 can store information for a total of 55 pieces. However, the appearance frequency storage unit 132 is not particularly limited to 55. It is desirable to design the appearance frequency storage unit 132 so as to store as large a number of information as possible within the memory of the authentication server 10 and the processing performance.

  The operation mode flag 133 is a flag for storing that the operation mode has been changed from the normal state to the block state when the indication of the brute force attack is detected. The operation mode flag 133 is set to either a normal state indicating that a brute force attack has not been received or a blocked state indicating that a brute force attack has been received.

  The authentication status flag 134 stores whether or not the correct username and password are input and the authentication is successful. The authentication status flag 134 is set to either an authentication status indicating a status of successful authentication or a non-authentication status indicating a status of failed authentication or a status before authentication.

  When storing the password or hash value for which the authentication process has failed anew in the password history storage unit 131 that stores the password for which the authentication process failed before receiving the correct password or the hash value corresponding to the password. The number of passwords or hash values evicted (lost) from the password history storage unit 131 is counted. The hash value is an example of the corresponding value of the password corresponding to the password.

  For example, in the password history storage unit 131a of the storage unit 13a for user A, four hash values that have failed in the latest, one before, two before, three before authentication processing are stored. In the present embodiment, a hash value is stored as the corresponding value of the password. However, instead of storing the hash value, the password itself may be stored in the password history storage unit 131a.

  In the case where a hash value that has failed in the latest, one previous, two previous, or three previous authentication processes is stored, in order to store in the password history storage unit 131a the hash value that has failed in the next authentication process, The hash value that failed in the authentication process three previous times by FIFO (First In First Out) is evicted from the password history storage unit 131a and lost. Then, the stored hash values are shifted one by one, and the hash values that have failed in the latest authentication process are newly stored in the password history storage unit 131a. The counting unit 15 counts the number of hash values lost from the password history storage unit 131a, and obtains a count value. In practice, the counting unit 15 counts the number of positive values of the area of each hash value of the appearance frequency storage unit 132.

  The authentication unit 16 performs an authentication process on an authorized user, and also uses the terminal device 20 to determine a “round-robin attack” in which all character string patterns are input in a round-robin manner. The authentication unit 16 checks the contents of the appearance frequency storage unit 132, and determines an indication of an attack from the number of positive areas in the appearance frequency storage unit 132 counted by the counting unit 15. In the determination of the brute force attack, when the count value is equal to or more than the predetermined number, the authentication unit 16 resets the count value without determining that the authentication process is successful when the input of the correct password is accepted. On the other hand, when the authentication unit 16 receives an input of a correct password when the count value is less than the predetermined number, it is determined that the authentication process has succeeded.

  The control unit 17 controls the entire authentication server 10. Further, the control unit 17 controls data storage in the storage unit 13 such as the password history storage unit 131 and the appearance frequency storage unit 132. Note that FIG. 2 is a block diagram focusing on functions, and a processor that executes software of each unit indicated by these functional blocks is hardware as shown in FIG. 3 as an example.

[Hardware configuration]
Next, the hardware configuration of the authentication server 10 according to the present embodiment will be described with reference to FIG. FIG. 3 shows an example of the hardware configuration of the authentication server 10 according to the present embodiment. The authentication server 10 includes an input device 101, an output device 102, an external I / F 103, a random access memory (RAM) 104, a read only memory (ROM) 105, a central processing unit (CPU) 106, a communication I / F 107, and an HDD (HDD). The hard disk drive 108 and the like are connected to one another by a bus B.

  The input device 101 includes a keyboard, a mouse and the like, and is used to input each operation signal to the authentication server 10. The output device 102 includes a display such as a liquid crystal display (LCD) monitor, a printer, a cathode ray tube (CRT), and the like, and outputs various processing results. The communication I / F 107 is an interface for connecting the authentication server 10 to a network. Thus, the authentication server 10 can perform data communication with another device (terminal device 20 or the like) via the communication I / F 107.

  The HDD 108 is a non-volatile storage device storing programs and data. The programs and data to be stored include basic software and application software that control the entire authentication server 10. For example, the HDD 108 may store various databases, programs, and the like.

  The external I / F 103 is an interface with an external device. The external device is, for example, a recording medium 103a. Thereby, the authentication server 10 can read and / or write the recording medium 103 a via the external I / F 103. The recording medium 103 a includes a CD (Compact Disk), a DVD (Digital Versatile Disk), an SD memory card (SD Memory card), a USB memory (Universal Serial Bus memory), and the like.

  The ROM 105 is a non-volatile semiconductor memory that can hold internal data even when the power is turned off. The ROM 105 stores programs and data such as network settings. The RAM 104 is a volatile semiconductor memory that temporarily holds programs such as an authentication program and data. The CPU 106 is an arithmetic device that realizes control of the entire apparatus and a built-in function by reading programs and data such as an authentication program from the storage device such as the HDD 108 and the ROM 105 onto the RAM 104 and executing processing.

  With this configuration, in the authentication server 10 according to the present embodiment, the CPU 106 executes an initialization process, an authentication process, and an attack determination process using, for example, the authentication program and data stored in the RAM 104, the ROM 105, and the HDD 108. The password history storage unit 131, the appearance frequency storage unit 132, the operation mode flag 133, the authentication status flag 134, the registered user name character string, and the password character string 135 are stored in the RAM 104, the HDD 108, or the network. It may be stored in a server on the cloud connected to the authentication server 10 or the like.

  Also, the function of the input reception unit 11 can be realized by the input device 101, for example. The functions of the input check unit 12, the password conversion unit 14, the count unit 15, the authentication unit 16, and the control unit 17 are realized by, for example, processing that the authentication program causes the CPU 106 to execute.

[Initialization process]
Next, the operation of the authentication server 10 according to the present embodiment will be described. First, an example of the initialization process performed by the authentication server 10 will be described with reference to FIG. FIG. 4 is a flowchart illustrating an example of the initialization process according to an embodiment.

  When the initialization process is started, the control unit 17 sets the state of the operation mode flag 133 stored in the storage unit 13 to "normal" (step S1). Next, the control unit 17 empties all the password history storage unit 131 (step S2). Next, the control unit 17 sets the values of all the regions of the appearance frequency storage unit 132 to 0 (step S3). Next, the control unit 17 sets the status of the authentication status flag 134 to "non-authentication" (step S4), and ends this processing. The above steps are performed for all registered users.

  As a result of the initialization processing being performed, the state of the storage unit 13 becomes empty for all registered users, as shown in FIG. "0" is set to all 55 areas of In addition, the operation mode flag is set to the “normal” state, which indicates that authentication by the attacker's password is not performed (authentication by the legitimate user's password). The authentication status flag is set to "non-authentication" indicating the status before authentication.

[Authentication process]
Next, an example of the authentication process performed by the authentication server 10 will be described with reference to FIGS. 6 and 7. 6 and 7 are flowcharts showing an example of an authentication process according to an embodiment. When the user inputs the user name and password from the login screen of the terminal device 20, the input accepting unit 11 accepts input of the user name and password (step S10), and sends it to the input checking unit 12.

  Next, the input check unit 12 refers to the storage unit 13 to determine whether the user name of a specific user is registered (step S12). For example, the input check unit 12 acquires information specifying the terminal device 20 together with the user name and password, determines the specific user from the information, and refers to the user name character string and password character string 135 of the specific user. Then, it may be determined whether the user name is registered. As information for specifying the terminal device 20, a serial number or the like of the device given to the terminal device 20 can be used.

  If the input check unit 12 does not match the user name character string of the specific user registered in the storage unit 13, the input check unit 12 determines that the input user name is not registered, and ends the present process. On the other hand, when the input check unit 12 matches the user name character string of the specific user, the input check unit 12 determines that the input user name is registered, and determines whether the password is correct (step S14).

  When the input check unit 12 matches the password character string of the specific user, the input check unit 12 determines that the input password is correct, and proceeds to step S16. If the input check unit 12 does not match the password character string of the specific user, the input check unit 12 determines that the input password is incorrect, and proceeds to the processing of FIG. 7 (step S30).

  In step S30, the control unit 17 determines whether the operation mode flag 133 is set to the "normal" state. When the operation mode flag 133 is not set to the “normal” state, the control unit 17 proceeds to step S40. If the operation mode flag 133 is set to the “normal” state, the control unit 17 proceeds to step S 32 and stores the hash value of the password previously input into the password history storage unit 131 by mistake. judge. If the control unit 17 determines that the password history storage unit 131 is not full with the hash value of the password incorrectly input before, the control unit 17 proceeds to step S40.

  In step S40, the hash values stored in the password history storage unit 131 are shifted one by one to the storage area in the old direction. In other words, the hash value stored in the area two areas before is shifted by one to the area three areas before, and the hash value stored in the area one area before is shifted one area into the area two areas before, The hash values stored in the area are stored shifted by one in the previous area.

  Next, the password conversion unit 14 calculates the hash value of the password determined to be erroneously input using the hash function (step S 42), and sets the calculated hash value to the latest area of the password history storage unit 131. It memorizes (step S44), and ends this processing.

  Thus, when an incorrect password is input, the password history storage unit 131 stores the hash value of the incorrectly input password. For example, when the correct password is "Himitsu", an example of the change of the password history storage unit 131 when the password is input erroneously as "himitsu" and then "Himitu" first is shown in FIG. In this case, since the password history storage unit 131 still has free space, the processes of steps S32 to S40 to S44 of FIG. 7 are performed, and the processes of steps S34 to S38 do not occur.

  Although the password is expressed as a character string in FIG. 8 to make the description easy to understand, the password is actually converted to a hash value and stored. However, the password history storage unit 131 may store the character string of the password as it is.

  Although the hashing algorithm used by the password conversion unit 14 is not particularly limited, in the example of the present embodiment, the number of areas of the appearance frequency storage unit 132 is set to 55, so the hash value generated by the password conversion unit 14 Is converted to a value between 0 and 54. For example, after the password conversion unit 14 simply adds the character code of each character included in the password character string, the password conversion unit 14 can use the remainder value divided by 55 as the hash value. In fact, there are existing algorithms that take as far as possible different values for similar input character strings, and it is desirable for the password conversion unit 14 to calculate hash values using these algorithms. The password conversion unit 14 may calculate a hash value for the password after the bit shift processing by performing processing such as adding a bit shift to each character of the password character string, for example.

  It is assumed that the user enters a password incorrectly twice in succession, and after the password history storage unit 131 is in the state of FIG. 8, the correct password “Himitsu” is input. In this case, the processes in steps S10 to S14 of FIG. 6 are performed, and in step S14, the input check unit 12 determines that the correct password has been input, and the control unit 17 sets the operation mode flag 133 to the “normal” state. It is determined whether or not there is (step S16).

  If the control unit 17 determines that the operation mode flag 133 is not set to the “normal” state, the process proceeds to step S26. When the control unit 17 determines that the operation mode flag 133 is set to the “normal” state, the control unit 17 sets the authentication state flag 134 to the “authentication” state indicating that the authentication is successful (step S18). That is, the authentication status flag 134 indicates that the password "Himitsu" entered this time has been authenticated as the correct password.

  Next, the control unit 17 subtracts 1 from the value of the area of the appearance frequency storage unit 132 corresponding to the hash value stored in the password history storage unit 131 (step S20). Next, the control unit 17 resets the lower limit value when the value of the area of the appearance frequency storage unit 132 which is “−1” in step S20 is smaller than the lower limit value (step S22).

  As described above, at the timing when the authentication status flag 134 is switched to the authenticated status, when at most four most recent erroneous passwords are stored in the password history storage unit 131, those passwords are erroneously input by the authorized user. It can be judged as an easy password. Therefore, in this case, “−1” is added to the value of the area in the appearance frequency storage unit 132 corresponding to the hash value stored in the password history storage unit 131. As described later, if the number of areas having a positive value in the appearance frequency storage unit 132 is a predetermined number or more, it is determined that the password authentication by the attacker is performed.

  After performing the processes of step S20 and step S22 of FIG. 6 for the number of hash values stored in the password history storage unit 131, the control unit 17 empties all the password history storage unit 131 (step S24), This process ends.

  In this embodiment, incorrect password input due to a brute force attack and incorrect password input due to a memory mistake or a typo of a legitimate user are caused by similarity (variation) with passwords input in the past. Determine.

  For this purpose, two types of areas, password history storage unit 131 and appearance frequency storage unit 132, are used. These two areas are prepared separately for each user. The password history storage unit 131 is an area for storing a predetermined number (four in the present embodiment) of the latest history of the input password character string. The number to be stored is not limited to a fixed number, and may be n (n ≧ 1). At this time, instead of storing the password character string as it is, a numerical value is stored using a hash function. By this mechanism, when the authorized user inputs the password correctly, it becomes possible to determine that the incorrect password stored in the password history storage unit 131 is a password that the authorized user is likely to make an error.

  For example, if the hash function is simply added to the character code of each character string and then divided by 55, the hash of the password that is likely to cause an error for a legitimate user, stored in the password history storage unit 131 of FIG. The values are calculated as follows.

"himitsu" = (0x68 + 0x69 + 0x6D + 0x69 + 0x74 + 0x73 + 0x75) / 55 = 1
"Himitu" = (0x48 + 0x69 + 0x6D + 0x69 + 0x74 + 0x75) / 55 = 19
In this case, the state of the appearance frequency storage unit 132 is as shown in FIG. That is, the box at the upper left of the area of the appearance frequency storage unit 132 is defined as the area corresponding to the hash value "0", and the first line from there corresponds to the hash values "1", "2", etc. in the right direction. Area. After the upper right "10" in the first line, the left end of the second line is the area corresponding to the hash value "11".

  Therefore, when the process of step S20 of FIG. 6 is executed, as shown in FIG. 9, the area corresponding to the hash value “1” of the password of the Himitsu password that is likely to be mistaken for the regular user and the hash of the password of “Himitu” "-1" is set in the area corresponding to the value "19".

  In step S22, a lower limit is provided for negative values that can be set in the appearance frequency storage unit 132. For example, when the lower limit value is set to "-3", the value set in the appearance frequency storage unit 132 is- It is controlled so as not to become a value smaller than three. The reason for setting the lower limit value is that if the lower limit is not set, the value set in the appearance frequency storage unit 132 decreases without limit each time the user repeats the same input error, and in the case of determination of a brute force attack, It is because it becomes difficult to be judged as a brute force attack forever.

  Next, the case where an incorrect password string of four patterns “aaa”, “aab”, “aac”, “AAA” is input will be described. With the above four patterns of password input, it is difficult to determine whether the legitimate user has entered the password by mistake or the password entered in the first four rounds of the brute force attack. In this state, it is assumed that one more incorrect password "AAB" is input.

  In this case, the processes of steps S10 to S14 of FIG. 6 are executed, it is determined as "No" at step S14, and the processes of steps S30 and S32 of FIG. 7 are executed. In step S32, the control unit 17 determines that the password history storage unit 131 is full.

  Therefore, next, the control unit 17 adds 1 to the value of the corresponding area of the appearance frequency storage unit 132 with respect to the hash value of the oldest password of the password history storage unit 131 (step S34). Next, when the value of the area after the addition becomes larger than one, the control unit 17 sets the value of the area to one (step S36). Next, the control unit 17 calls an attack determination process (step S38). The called attack determination process shown in FIG. 10 is mainly executed by the authentication unit 16 and the counting unit 15. After the process of FIG. 10, the process returns to FIG. 7 to process steps S40 to S44.

  At this point in time, the password "aaa" stored in the third area of the password history storage unit 131 shown in FIG. 11A is entered when another incorrect password "AAB" is input. As shown in FIG. 11B, the data is erased from the password history storage unit 131. At this time, the value of the corresponding area of the appearance frequency storage unit 132 corresponding to the “aaa” that has been eliminated (expelled) is “+1”.

The hash value of "aaa" is 16 by the following calculation.
"aaa" = (0x61 + 0x61 + 0x61) / 55 = 16
Therefore, as shown in FIG. 11C, the area of the appearance frequency storage unit 132 corresponding to the hash value 16 is +1. In FIGS. 11 (a) and 11 (b), the password is expressed as a character string to make the description easy to understand, but in practice the password history storage unit 131 stores the hash value of the password. .

  When the attack determination process of FIG. 10 is started in the state of the appearance frequency storage unit 132 shown in FIG. 11C, the count unit 15 indicates a variable indicating the number of areas having a positive value of the appearance frequency storage unit 132. The counter C is set to "0" (step S50).

  Next, the authentication unit 16 sets “0” to the value of the variable N indicating the position of the area of the appearance frequency storage unit 132 (step S52). The variable N of “0” indicates the top position of the appearance frequency storage unit 132 of FIG. 11C, that is, the top left position.

  Next, the authentication unit 16 determines whether the Nth value of the appearance frequency storage unit 132 is a positive value (step S54). If the authentication unit 16 determines that the Nth value of the appearance frequency storage unit 132 is not a positive value, the process proceeds directly to step S58. On the other hand, when the authentication unit 16 determines that the Nth value of the appearance frequency storage unit 132 is a positive value, the counting unit 15 adds “1” to the counter C (step S56), and proceeds to step S58.

  In step S58, the authentication unit 16 adds “1” to the variable N, and changes the area of the appearance frequency storage unit 132 to the next area, that is, the Nth (step S58). Next, the authentication unit 16 determines whether the end of the area of the appearance frequency storage unit 132 has been checked (step S60). For example, the authentication unit 16 determines “Yes” when the value of N is 55, and determines “No” when the value of N is less than 55. If the authentication unit 16 determines that the end of the area of the appearance frequency storage unit 132 has not been checked, the process returns to step S54, and determines whether the Nth value of the appearance frequency storage unit 132 is a positive value. That is, steps S54 to S60 are repeated until it is checked whether each area is a positive value from the top (0th) area to the last area (54th) of the appearance frequency storage unit 132. If the authentication unit 16 determines in step S60 that the last area of the appearance frequency storage unit 132 has been checked, the authentication unit 16 determines whether the number of counters C is equal to or greater than a predetermined number (step S62). Assuming that the predetermined number is set to 10 in advance, for example, in the case of FIG. 11C, the number of counters C is one. Therefore, in step S62, the authentication unit 16 determines that the number of counters C is less than 10, determines that no brute force attack has occurred, and ends the present process.

Further, when the wrong password is input three times, the places corresponding to the following hash values of the password which are erased from the password history storage unit 131 are incremented by one.
"aab" = (0x61 + 0x61 + 0x62) / 55 = 17
"aac" = (0x61 + 0x61 + 0x63) / 55 = 18
"AAA" = (0x41 + 0x41 + 0x41) / 55 = 30
At this time, the processing of steps S10 to S14 of FIG. 6 and steps S30 to S38 of FIG. 7 are shifted to the time, and in the attack determination processing shown in FIG. The count C counts the number of areas having a positive value 132.

  FIG. 12A shows the state of the appearance frequency storage unit 132 as a result of adding 1 to the place corresponding to the hash value of each password of “aab”, “aac”, and “AAA”. In this case, 4 is set to the count C. In this case, in step S62 of FIG. 10, the authentication unit 16 determines that the number of counters C is less than 10, determines that a brute force attack has not occurred, and ends the present process.

  Every time the appearance frequency storage unit 132 is updated, the counting unit 15 counts the number of areas having a positive value, and the authentication unit 16 exceeds the predetermined number (10 in this embodiment). It is determined that a brute force attack has occurred (step S62). Then, the authentication unit 16 changes the operation mode flag 133 from the "normal" state to the "block" state (step S64).

  For example, in the appearance frequency storage unit 132 illustrated in FIG. 12B, 10 is set in the count C. In this case, in step S62 of FIG. 10, the count unit 15 determines that the number of counters C is 10 or more, and the authentication unit 16 determines that a brute force attack has occurred. As a result of this determination, the operation mode flag 133 is changed from the “normal” state to the “block” state. When the operation mode flag 133 is in the “block” state, it indicates that “authentication by an attacker's password is being performed”.

  As described above, in the present embodiment, when erroneous passwords are continuously input, the appearance frequency storage unit 132 generates a hash value representing a password that has been evicted (lost) from the password history storage unit 131. The frequency of input is stored as a negative value, and is stored as a password that is easily input by an authorized person. Also, in the case of brute force attack, since the password to be input is different every time, there is a high possibility that the hash value obtained by digitizing the password will also have different values. Therefore, as indicated by the positive value area of the appearance frequency storage unit 132 that is predicted to be subjected to a brute force attack, if various hash values are accumulated over a predetermined number of areas or more, this is considered as a brute force attack It can be regarded as a sign.

  Further, in the present embodiment, the appearance frequency storage unit 132 is used to store that the signs of the brute force attack have been captured, and the operation mode flag 133 (storage area) for switching the operation mode is prepared for each user. There is. When a brute force attack is received, the operation mode flag 133 switches from the normal state to the block state, and in this state, even if the correct password is input, the operation does not pass authentication.

  That is, when the correct password is input when the operation mode flag 133 is in the block state, the processes of steps S10 to S16 in FIG. 6 are executed, and it is determined as "No" in step S16. In this case, the authentication unit 16 sets the operation mode flag 133 to the “normal” state (step S26). Next, the authentication unit 16 checks all the appearance frequency storage unit 132, and sets an area having a positive value to “0” (step S28). Thereby, the count value which has counted the state which has received brute force attack by the number of the area | regions of the positive value of the appearance frequency memory | storage part 132 is reset. The control unit 17 empties all the password history storage unit 131 (step S24), and the process ends.

  As a result, even if the correct password is inputted once during the brute force attack, the operation mode flag 133 is only switched from the “blocked” state to the “normal” state, and the authentication is not successful. Therefore, authentication can be performed for the input of the correct password during the brute force attack, and the password can be prevented from being leaked. In this mechanism, authentication does not succeed even if the regular user inputs the correct password when the operation mode flag 133 is in the block state, but in the case of the regular user, if authentication fails, it is suspected of incorrect entry of the user name and password. Enter the correct password again. At this time, since the authorized user succeeds in authentication, there is no inconvenience that the authentication does not succeed even if the authorized user inputs the correct password again.

  On the other hand, in the case of a brute force attack, by its nature, it is extremely unlikely that the correct password will be entered again after accidentally entering the correct password and failing in authentication during the brute force attack. From the above, according to the authentication process and the attack determination process according to the present embodiment, it is possible to prevent the authentication by the password of the attacker without inhibiting the authentication by the password of the authorized user.

  The operation mode flag 133 is an example of operation mode information indicating whether or not the authentication is based on the password of the attacker, and is set to the normal state or the blocked state. The normal state is a state of the first mode indicating that the authentication is not based on the attacker's password, and the blocked state is a state of the second mode indicating that the authentication is based on the attacker's password.

  In the present embodiment, a brute force attack is described as an example of authentication using an attacker's password, but authentication using an attacker's password includes a dictionary attack. Since a password whose password is completely random is difficult for the user to memorize and input, a password is often set based on existing words. In such a case, an attacker may succeed in authentication with a much smaller number of attempts than brute force by preferentially inputting a password created according to a dictionary of existing words instead of brute force. Authentication using an attacker's password using this method is called a dictionary attack.

  As described above, in the present embodiment, each time the user inputs a password, the password is hashed and accumulated in the password history storage unit 131. When the correct password is input in the state where the history of the input password is stored, the maximum n passwords stored in the password history storage unit 131 are judged as the password incorrectly input by the authorized user, and the appearance frequency storage is stored. A value of “negative” is added to the part 132 and stored.

  If an incorrect password entry continues without entering a correct password, the hash value of the password evicted beyond the storable number in the password history storage unit 131 has a value of "positive" in the appearance frequency storage unit 132. I will memorize in the form to add.

  Every time a password is input, the number of regions having a “positive” value is checked in the appearance frequency storage unit 132, and if the number exceeds a predetermined number determined in advance, it is determined as a sign of a brute force attack. Then, the authentication unit 16 switches the operation mode flag 133 to a state in which authentication is blocked. If a brute force attack continues, the correct password will be entered eventually, but in the blocked state, even if the correct password is entered, the authentication fails because it is treated as an authentication failure.

  Once in the blocked state, updating of the appearance frequency storage unit 132 becomes unnecessary even if an incorrect password is input thereafter. A brute force attack then continues, and there is a possibility that the correct password may be input in the future, but even if the correct password is input, authentication fails if the operation mode flag 133 is in the blocked state. For this reason, even if a correct password is input by brute force attack, unauthorized authentication can be prevented and password leakage can be prevented.

  Once the correct password is entered in the blocked state, the operation mode flag 133 is returned to the normal state. At that time, in the appearance frequency storage unit 132, the value of “+1” or more is returned to “0”. Even if the brute force attack continues thereafter, the brute force attack does not enter the correct password again because the authentication failure is once replied to the correct password. Therefore, an attack with the same password as the correct password entered once is not performed, and security is protected. In addition, when the brute force attack continues, even after the area of the appearance frequency storage unit 132 is once returned to “0”, the area of “+1” or more increases immediately and becomes a block state again.

  As described above, in the present embodiment, in the authentication system 1 managed by two character strings of the user name and the password, a mechanism for preventing unauthorized use of the terminal device 20 and leakage of account information by a method such as brute force attack is realized. be able to.

  In the present embodiment, the password history storage unit 131 stores a hash value obtained by digitizing the latest plurality of password character strings input in the past for each user name using a hash function. Also, the appearance frequency of the past incorrect input password is analyzed using the appearance frequency storage unit 132 that records for each hash value. This makes it possible to guard against successful authentication even if the correct username and password are entered if signs of brute force attack or dictionary attack are observed. In addition, in the present embodiment, a false password input due to an input error of the regular user or a memory mistake is stored as a “negative” value in the appearance frequency storage unit 132 in a form of a brute force attack. Implement a mechanism that is difficult to

  As described above, the authentication system 1 can prevent authentication by the attacker's password without disturbing authentication by the password of the authorized user.

[Modification]
Next, the configuration of the authentication server 10 according to the modification of the embodiment will be described with reference to FIG. FIG. 13 shows an example of a functional configuration of the authentication server 10 according to a modification of the embodiment.

  In many cases, an attacker does not manually input a messy string, but automatically sequentially inputs a string generated with reference to a string generated by a particular program algorithm or a word dictionary. Therefore, when an attacker performs a brute-force attack on a plurality of users of one terminal device 20 or different terminal devices 20 using the same attack program, “positive” stored in the appearance frequency storage unit 132 It is considered that the range and appearance order of the value of will be almost the same.

  In the above embodiment, when the frequency of appearance at ten places is counted, it is judged as a sign of a total hit attack. In this modification, the information of the appearance frequency storage unit 132 at the time of the determination is shared by other systems and other users, and the same generation pattern is determined by the other users, which is twice the maximum at 10 locations. It is possible to judge a brute force attack at an early stage.

  Therefore, the authentication server 10 according to the modification of FIG. 13 realizes a mechanism in which the information of the appearance frequency storage unit 132 can be shared by other users or other devices. This makes it possible to catch signs of brute force attacks earlier than usual, and reduce the risk of password leakage even if the correct password is entered accidentally by the early attacks. That is, it is possible to reduce the possibility of the password being leaked when the correct password is inputted by chance by the attacker in the early stage before the state of blocking changes.

  Specifically, in the authentication server 10 according to the modification of the embodiment shown in FIG. 13, an appearance frequency sharing storage unit 200 is added to the authentication server 10 according to the embodiment shown in FIG. Only the point is different. The appearance frequency shared storage unit 200 has the same structure as the appearance frequency storage unit 132 for each user, and when any user detects a sign of a brute force attack, its contents are copied, and an attack with another user is made. The appearance frequency storage unit 132 copied when performing the determination can be referred to. Data of one or more appearance frequency storage units 132 may be copied to the appearance frequency shared storage unit 200.

  FIG. 14 illustrates an example of the states of the appearance frequency storage unit 132 and the appearance frequency sharing storage unit 200 according to a modification of the embodiment. Here, an example is shown in which the indication of an attack on the terminal device 20 of the user A is shared with the terminal device for the user B.

  In a state where an attack is not performed, an appearance frequency storage section 132a shown in FIG. 14A of the user A storage section 13a and an appearance frequency storage section 132b shown in FIG. 14B of the user B storage section 13b. Is in a different state due to a past input error or the like of each user. Further, nothing is stored in the appearance frequency sharing storage unit 200 whose example is shown in FIG. 14C in the initial state.

  When an attacker has launched a brute force attack on user A, if the appearance frequency storage unit 132a detects a sign of a brute force attack, the appearance frequency storage unit 132a of user A is detected frequency of occurrence shared memory unit at the detected timing. Save to 200. In FIG. 15, since the positive region of the appearance frequency storage unit 132a is 10 or more places and it is determined to be a brute force attack, the data of the appearance frequency storage unit 132a of FIG. A state of being copied to the appearance frequency shared storage unit 200 is shown.

  When data is stored in the appearance frequency shared storage unit 200, the authentication unit 16 performs determination with reference to the appearance frequency storage unit 132 and the appearance frequency shared storage unit 200. FIG. 16 is a flowchart illustrating an example of the attack determination process according to the modification of the embodiment. In the present modification, the attack determination process of FIG. 16 is called instead of the attack determination process of FIG. 10 called in step S38 of FIG. In the attack determination process of FIG. 16, the description is simplified by attaching the same step number as the step number of FIG. 10 to the step performing the same process as the attack determination process of FIG. 10.

  Here, the attack determination process according to the modification is described using the flowchart of FIG. 16 for the login operation of user A, and the attack determination process for login operations of user B and other users is described by user A's. Since the process is the same as in the case, the description is omitted.

  When the process of FIG. 16 is started, the processes of steps S50 to S56 are performed. In step S54, the authentication unit 16 determines whether the Nth value of the appearance frequency storage unit 132 is a positive value. If the authentication unit 16 determines that the Nth value of the appearance frequency storage unit 132 is not a positive value, the process proceeds directly to step S78. On the other hand, when the authentication unit 16 determines that the Nth value of the appearance frequency storage unit 132 is a positive value, the counting unit 15 adds “1” to the counter C (step S56), and proceeds to step S78.

  In step S78, the authentication unit 16 determines whether the N-th occurrence frequency shared storage unit 200 is a positive value. If the authentication unit 16 determines that the Nth value of the occurrence frequency shared storage unit 200 is not a positive value, the process proceeds to step S58. On the other hand, when the authentication unit 16 determines that the N-th occurrence frequency shared storage unit 200 is a positive value, the counting unit 15 adds “1” to the counter C (step S80), and proceeds to step S58. .

  In step S58, the authentication unit 16 adds “1” to the variable N, and changes the area of the appearance frequency storage unit 132 to the next area, ie, the Nth. Next, the authentication unit 16 determines whether the end of the area of the appearance frequency storage unit 132 has been checked (step S60). For example, the authentication unit 16 determines “Yes” when the value of N is 55, and determines “No” when the value of N is less than 55. If the authentication unit 16 determines that the end of the area of the appearance frequency storage unit 132 has not been checked, the process returns to step S54, and determines whether the Nth value of the appearance frequency storage unit 132 is a positive value. That is, the processes of steps S54, S56, S78, S80, S58, and S60 are repeated until the area from the top (0th) area to the last area (54th) of the appearance frequency storage unit 132 is checked. If it is determined in step S60 that the authentication unit 16 has checked the end of the area, it is determined whether the number of counters C is equal to or greater than a predetermined number (step S62).

  For example, counting the number of matching areas of the appearance frequency storage unit 132a shown in FIG. 17A and the appearance frequency sharing storage unit 200 shown in FIG. 17C, the number of counters C is 20. . Assuming that the predetermined number is 10, in step S62, the authentication unit 16 determines that the number of counters C is equal to or greater than the predetermined number, determines that a brute force attack is being performed, and sets the operation mode flag 133 to The "block" state is set (step S64), and the present process ends.

  As described above, in the attack determination process according to the modification of the embodiment, data is present in the appearance frequency sharing storage unit 200, and both the appearance frequency storage unit 132 for each user and the appearance frequency sharing storage unit 200 If the same place is "positive", the number of additions of the counter C is doubled. As a result, the count increase upon receiving the same brute force attack is doubled at the maximum at maximum, rather than each user individually detecting the number of "positive" value areas in the appearance frequency storage unit 132. You can catch signs of a brute force attack up to twice as fast.

  Further, although the appearance frequency sharing storage unit 200 is one in the above description, a plurality of this is prepared, and signs of brute force attacks are detected by a plurality of users, and when the appearance patterns differ, each copy is used It is also good. Also, even a single user may save a copy each time he has captured multiple attacks. When there are a plurality of appearance frequency shared storage units 200, the authentication unit 16 repeats the determination for the number of appearance frequency shared storage units 200.

  According to the authentication server 10 according to the modification of the embodiment, data of the appearance frequency storage unit 132 of one user is transferred to the appearance frequency share storage unit 200 of the authentication server 10, and a brute force attack on another user is performed. It can be used when making a decision. In addition, since the appearance frequency storage unit 132 to be transferred does not include the correct password input by the user or the direct character string of the incorrect password history, there is little risk that the password may be leaked at the time of sharing. There is.

  In the above, the authentication server 10 which concerns on one Embodiment, and the authentication server 10 which concerns on the modification were demonstrated. According to the authentication server 10 according to the present embodiment and its modification, password leakage in a brute force attack and a dictionary attack can be prevented, so that the user can easily use a password without being forced to set complicated password setting rules. It can be set.

  Also, since passwords that are prone to input errors are stored using the password history storage unit 131 and the appearance frequency storage unit 132 is weighted “negative” according to the incorrect password input frequency, the total is immediately set. It is not judged to be a hit attack. Therefore, there is no disadvantage that the account is locked if the password is incorrect the predetermined number of times.

  In addition, since the hashed numerical value is used for the attack determination of the password string and storage of the past input password, there is no need to store the input string itself inside the system. As a result, the processing speed can be increased, the required amount of memory can be reduced, and the security can be improved.

  The authentication apparatus, the authentication program, and the authentication method have been described above according to the above embodiments, but the authentication apparatus, the authentication program, and the authentication method according to the present invention are not limited to the above embodiments, and various modifications are possible within the scope of the present invention Variations and improvements are possible. Moreover, when there exist two or more said embodiment and modification, it can combine in the not inconsistent range.

The following sections will be further disclosed regarding the above description.
(Supplementary Note 1)
When storing a password for which authentication processing has failed anew or a corresponding value of the password in a storage unit for storing a predetermined number of passwords for which authentication processing has failed before receiving a correct password or the corresponding value of the password A counting unit that counts the number of lost passwords or corresponding values of the passwords;
An authentication unit that resets the counted value without determining that the authentication processing is successful when the input of the correct password is accepted when the counted value is equal to or greater than a predetermined number;
An authentication device having
(Supplementary Note 2)
The authentication unit determines that the authentication processing is successful when the input of the correct password is accepted when the counted value is less than a predetermined number.
The authentication device according to appendix 1.
(Supplementary Note 3)
If the counted value is equal to or more than a predetermined number, the authentication unit indicates that the operation mode information is an authentication by a password of an attacker from a first mode indicating that authentication by the password of the attacker is not performed. Switch to mode
When the counted value is equal to or more than a predetermined number, operation mode information is switched to the first mode when an input of a correct password is accepted,
The counting unit is the same as the password or the corresponding value of the password that disappears from the storage unit in the first mode state or the password that disappears from the storage unit in the second mode state. In the case of, excluding at least once from the counted number,
The authentication device according to Appendix 1 or 2.
(Supplementary Note 4)
When storing a password for which authentication processing has failed anew or a corresponding value of the password in a storage unit for storing a predetermined number of passwords for which authentication processing has failed before receiving a correct password or the corresponding value of the password A process of counting the number of lost passwords or corresponding values of the passwords;
A process of resetting the counted value without determining that the authentication process is successful when the input of a correct password is accepted when the counted value is equal to or greater than a predetermined number;
An authentication program to make a computer run.
(Supplementary Note 5)
If the counted value is less than a predetermined number, it is determined that the authentication process has succeeded when the input of the correct password is accepted.
The certification program described in Appendix 4.
(Supplementary Note 6)
When the counted value is equal to or more than a predetermined number, the operation mode information is switched from a first mode indicating that the authentication is not based on the password of the attacker to a second mode indicating that the authentication is based on the password of the attacker;
When the counted value is equal to or more than a predetermined number, operation mode information is switched to the first mode when an input of a correct password is accepted,
If at least one of the password or the corresponding value of the password lost from the storage unit in the second mode state has the same value as the password or the corresponding value of the password lost from the storage unit in the first mode state, Times are excluded from the counted number,
The authentication program according to appendix 4 or 5.
(Appendix 7)
When storing a password for which authentication processing has failed anew or a corresponding value of the password in a storage unit for storing a predetermined number of passwords for which authentication processing has failed before receiving a correct password or the corresponding value of the password Count the number of lost passwords or their corresponding values,
When the counted value is equal to or more than the predetermined number, when the input of the correct password is accepted, the counted value is reset without determining that the authentication process is successful.
An authentication method that a computer performs.
(Supplementary Note 8)
If the counted value is less than a predetermined number, it is determined that the authentication process has succeeded when the input of the correct password is accepted.
The authentication method according to appendix 7.
(Appendix 9)
When the counted value is equal to or more than a predetermined number, the operation mode information is switched from a first mode indicating that the authentication is not based on the password of the attacker to a second mode indicating that the authentication is based on the password of the attacker;
When the counted value is equal to or more than a predetermined number, operation mode information is switched to the first mode when an input of a correct password is accepted,
If at least one of the password or the corresponding value of the password lost from the storage unit in the second mode state has the same value as the password or the corresponding value of the password lost from the storage unit in the first mode state, Times are excluded from the counted number,
The authentication method according to appendix 7 or 8.

Reference Signs List 1 authentication system 10 authentication server 11 input reception unit 12 input check unit 13 storage unit 13a storage unit for user A 14 password conversion unit 15 count unit 16 authentication unit 17 control unit 20 terminal device 30 network 131a, 131 password history storage unit 132a, 132 appearance frequency storage unit 133a, 133 operation mode flag 134a, 134 authentication status flag

Claims (5)

When storing a password for which authentication processing has failed anew or a corresponding value of the password in a storage unit for storing a predetermined number of passwords for which authentication processing has failed before receiving a correct password or the corresponding value of the password A counting unit that counts the number of lost passwords or corresponding values of the passwords;
An authentication unit that resets the counted value without determining that the authentication processing is successful when the input of the correct password is accepted when the counted value is equal to or greater than a predetermined number;
An authentication device having The authentication unit determines that the authentication processing is successful when the input of the correct password is accepted when the counted value is less than a predetermined number.
The authentication device according to claim 1. If the counted value is equal to or more than a predetermined number, the authentication unit indicates that the operation mode information is an authentication by a password of an attacker from a first mode indicating that authentication by the password of the attacker is not performed. Switch to mode
When the counted value is equal to or more than a predetermined number, operation mode information is switched to the first mode when an input of a correct password is accepted,
The counting unit is the same as the password or the corresponding value of the password that disappears from the storage unit in the first mode state or the password that disappears from the storage unit in the second mode state. In the case of, excluding at least once from the counted number,
The authentication device according to claim 1. When storing a password for which authentication processing has failed anew or a corresponding value of the password in a storage unit for storing a predetermined number of passwords for which authentication processing has failed before receiving a correct password or the corresponding value of the password A process of counting the number of lost passwords or corresponding values of the passwords;
A process of resetting the counted value without determining that the authentication process is successful when the input of a correct password is accepted when the counted value is equal to or greater than a predetermined number;
An authentication program to make a computer run. When storing a password for which authentication processing has failed anew or a corresponding value of the password in a storage unit for storing a predetermined number of passwords for which authentication processing has failed before receiving a correct password or the corresponding value of the password Count the number of lost passwords or their corresponding values,
When the counted value is equal to or more than the predetermined number, when the input of the correct password is accepted, the counted value is reset without determining that the authentication process is successful.
An authentication method that a computer performs.

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