Patent Publication Number: US-9838205-B2

Title: Network authentication method for secure electronic transactions

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part (CIP) of co-pending U.S. patent application Ser. No. 14/488,255, entitled “NETWORK AUTHENTICATION METHOD FOR SECURE ELECTRONIC TRANSACTIONS”, filed on Sep. 16, 2014. 
    
    
     FIELD 
     The disclosure relates to network transaction authentication, and more particularly to a network authentication method for secure electronic transactions. 
     BACKGROUND 
     Online web-based services are widely used today, typical examples being online banking services and online shopping services. However, problems associated with transaction security have posed serious challenges and risks to institutions and their customers. In a global economy with billions of transactions carried daily over insecure public Internet Protocol (IP) networks, identity and/or personal information protection becomes paramount. In general, a customer computer environment is considered to be insecure due to its vulnerability to a variety of malicious software, such as keystroke recorder, Trojan horse, or even screen recorder, etc., that are able to record keystrokes, redirect critical messages to a fake server, or effectively “video record” a computer screen. Through a variety of means, hackers are able to steal customer identities and/or personal information. Even worse, critical data may be modified. 
     The traditional way to authenticate a customer is for a client computer to provide a user-id and a password. However, this one-factor (e.g., the combination of a user-id and a password) authentication is not secure enough to protect either the customer or the institution from attacks by malicious software or malware (including Trojan horses) using approaches, such as man-in-the-middle (MITM), man-in-the-browser (MITB), and keystroke logging. 
     Since the user-id and the password may be stolen, an identity verification device, e.g., a universal serial bus (USB) device loaded with a public key infrastructure (PKI) certificate, an integrated circuit (IC) electronic card or a dynamic token, may additionally be used for verifying the identity of the customer, thereby making the cost of customer service for personalization, distribution and troubleshooting considerable. Further, the necessity of having different identify verification devices for different institutions proves to be quite inconvenient for customers. 
     Therefore, there is still room for improvement in the above techniques. 
     SUMMARY 
     Therefore, an object of the disclosure is to provide a network authentication for secure electronic transactions that can overcome the aforesaid drawbacks. 
     According to the disclosure, there is provided a network authentication method to be implemented using a client device and a verification server that are connected to a communication network. The client device is associated with an end user and stores an authentication application. The network authentication method of the disclosure includes the steps of: 
     a) storing, by the verification server, a certificate that is assigned to the end user, and a public key that corresponds uniquely to the certificate, the certificate including a unique user identifier (UID) of the end user; 
     b) storing, by the client device, a certificate reference that is mapped uniquely to the certificate assigned to the end user, and a reference first private key portion that is obtained by encrypting a first private key portion of a private key with a personal identification number (PIN) code, which is determined by the end user, the public key and the private key cooperatively constituting an asymmetric key pair corresponding to the end user, the private key being capable of being divided into the first private key portion and a second private key portion; 
     c) by the client device, after receipt of the second private key portion and of transaction data that is associated with an electronic transaction between the client device and a network server and that is to be confirmed by the end user, in response to execution of the authentication application, generating a user input code through an input operation, decrypting the reference first private key portion stored in step b) with the user input code to obtain a current key portion, combining the current key portion and the second private key portion into a current key, and generating a digital signature for the transaction data using the current, key and the transaction data; and 
     d) by the verification server, upon receipt of a digital signature and a certificate reference via the communication network, determining, based on the public key corresponding to the certificate to which the certificate reference received thereby is uniquely mapped, whether or not the digital signature received thereby is signed with the private key, and obtaining front the digital signature received thereby the transaction data that has been determined, to be associated with the end user and that has been confirmed by the end user when it is determined that the digital signature is signed with the private key. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features end advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is a schematic block diagram illustrating a system that is configured for implementing a network authentication method according to the embodiment of the disclosure; 
         FIGS. 2A and 2B  cooperatively illustrate a registration procedure of the network authentication method of the embodiment, where an authentication server generates an asymmetric key pair; 
         FIGS. 2A and 2C  cooperatively illustrate a variation of the registration procedure, where a client device generates the asymmetric key pair; and 
         FIGS. 3A, 3B and 3C  cooperatively illustrate a procedure of how an electronic transaction is conducted in the system of  FIG. 1  according to the network authentication method of the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a system  100  is used to implement a network authentication method for secure electronic transactions according to the embodiment of the disclosure. The system  100  includes a network server  1  (e.g., an Internet content provider or ICP), a client device  2 , a verification server  3  (e.g., a certificate authority or CA) and an authentication server  4  that are connected to a communication network  400 , such as the Internet. Particularly, the network server  1  communicates with the client device  2  via a first communication channel  401  in the communication network  400 , with the verification server  3  via a second communication channel  402  in the communication network  400 , and with the authentication server  4  via a third communication channel  403  in the communication network  400 . The verification server  3  communicates with the authentication server  4  via a fourth communication channel  404  in the communication network  400 . The client device  2  communicates with the authentication server  4  via a fifth communication channel  405  in the communication network  400 . The first, second, third, fourth and fifth communication channels  401 ˜ 405  are different from one another. Accordingly, it is relatively difficult to attack the first to fifth communication channels  401 ˜ 405  simultaneously for stealing information associated with an end user  5 . 
     For exemplary purposes, the network server  1  may be, but is not limited to, a web bank server. The verification server  3  includes a database unit (not shown in the drawings) for storing therein a certificate  31  that is to be assigned to the end user  5 , a certificate reference  32  that is mapped uniquely to the certificate  31 , and a public key  312  that corresponds uniquely to the certificate  31 . The certificate  31  includes a unique user identifier (UID)  311  of the end user  5 . The public key  312  and a private key cooperatively constitute an asymmetric key pair which corresponds to the end user  5 . It is noted that, in this embodiment, the private key is capable of being divided into a first private key portion (not shown in the drawings) and a second private key portion  315 . In addition, the verification server  3  is able to issue certificates to users, and is further regarded as a trusted third party appointed by the authentication server  4  and the network server  1  to perform verification for signature and data. 
     The client device  2  is used by the end user  5 , and may be an electronic device capable of Internet browsing or data communication, such as a personal computer, a notebook computer, a smart phone, a tablet computer, etc. The client device  2  includes a plurality of hardware components (not shown in the drawings), such as a central processing unit, a basic input/output system (BIOS) unit, a storage unit, a network interface unit, a motherboard, etc., each of which has a unique identification code (not shown in the drawings). The storage unit of the client device  2  stores a service application  21  associated with the network server  1 , an authentication application  22  associated with network authentication, the certificate reference  32 , and a reference first private key portion  23  obtained by encrypting the first private key portion with a personal identification number (PIN) code that is determined by the end user  5 . The authentication server  4  stores the second private key portion  315 , and reference hardware identification data  41  that is associated with the UID  311  of the end user  5  and that is used to verify the identity of the client device  2 . 
     Referring to  FIGS. 1, 2A and 2B , the system  100  implements a registration procedure of the network authentication method according to the embodiment of the disclosure. The registration procedure of the network authentication method illustrates how the public key  312  is stored to the verification server  3 , how the certification reference  32  and the reference first private key portion  23  are stored in the client device  2  and how the reference hardware identification data  41  and the second private key portion  315  are stored in the authentication server  4 , and includes the following steps. 
     In step S 201 , upon execution of the service application  21  on the client device  2 , the end user  5  inputs user login data using a user input interface (not shown in the drawings) of the client device  2  at a website provided by the network server  1 . The user login data is then sent from the client device  2  to the network server  1  via the first communication channel  401 . In this embodiment, the user login data includes a user identification serving as the UID  311 , and a password. 
     In step S 202 , upon receipt of the user login data from the client device  2 , the network server  1  determines whether the user login data is correct. If the result is affirmative, the network server  1  sends a successful login message to the client device  2  via the first communication channel  401  (step S 203 ). Otherwise, the network server  1  sends an error message to the client device  2  for displaying on a display unit (not shown in the drawings) of the client device  2  (step S 200 ). 
     In step S 204 , upon receipt of the successful login message from the network server  1 , the client device  2  sends, through the executed service application  21 , a registration request for the end user  5  to the network server  1  via the first communication channel  401 . 
     In step S 205 , in response to receipt of the registration request from the client device  2 , the network server  1  sends a certificate request for the end user  5  to the verification server  3  via the second, communication channel  402 . The registration request includes the UID  311  of the end user  5 . 
     In step S 206 , in response to receipt of the certificate request from the network server  1 , the verification server  3  assigns the certificate  31  to the end user  5 , and generates one certificate reference  32  that is mapped uniquely to the certificate  31 . The verification server  3  stores the certificate  31  and the certificate reference  32  in the database unit, and sends the certificate reference  32  to the network server  1  via the second communication channel  402 . 
     In step S 207 , upon receipt of the certificate reference  32  from the verification server  3 , the network server  1  sends an authentication registration request for the end user  5  to the authentication server  4  via the third communication channel  403 . The authentication registration request includes the UID  311  of the end user  5 , and the certificate reference  32  received by the network server  1 . 
     In step S 208 , in response to receipt of the authentication registration request from the network server  1 , the authentication server  4  generates an authentication code (e.g., a one-time code), and sends the authentication code to the network server  1  via the third communication channel  403 . 
     In step S 209 , upon receipt of the authentication code from the authentication server  4 , the network server  1  sends the authentication code received thereby to the client device  2  via the first communication channel  401 . 
     In step S 210 , in response to receipt of the authentication code from the network server  1 , the client device  2  executes the authentication application  22  to generate hardware scanning data that is associated with the identification codes of the hardware components of the client device  2  and to send the authentication code received thereby and the hardware scanning data generated thereby to the authentication server  4  via the fifth communication channel  405 . 
     In step S 211 , upon receipt of the hardware scanning data and the authentication code from the client device  2 , the authentication server  4  verifies whether the authentication code received thereby matches the authentication code generated in step S 208 . If the result is affirmative, the flow goes to step S 212 . Otherwise, the authentication server  4  sends an error message to the client device  2  for displaying on the display unit of the client device  2  (step S 213 ). 
     In step S 212 , the authentication server  4  generates the asymmetric key pair including the public key  312  and the private key, divides the private key into the first private key portion and the second private key portion  315 , stores the second private key portion  315  and the hardware scanning data received thereby as the reference hardware identification data  41  that is associated with the UID  311  of the end user  5  and that is used to verify the identity of the client device  2 , sends the public key  312  to the verification server  3  via the fourth communication channel  404 , and sends the first private key portion and the certificate reference  32  received thereby in the beginning of step S 208  to the client device  2  via the fifth communication channel  405  to the client device  2 . 
     Following step S 212 , in step S 214 , upon receipt of the first private key portion and the certificate reference  32  from the authentication server  4 , through the executed authentication application  22 , the client device  2  generates the PIN code through an input operation of the user input interface by the end user  5 , and encrypts the first private key portion with the PIN code generated thereby to generate the reference first private key portion  23 . Finally, the client device  2  stores the reference first private key portion  23  and the certificate reference  32  in the storage unit. 
     Following step S 212 , in step S 215 , upon receipt of the public key  312  from the authentication server  4 , the verification server  3  stores the public key  312  received thereby in the database unit. Accordingly, the registration procedure associated with the end user  5  is completed. 
     It is noted that, in the above registration procedure, the asymmetric key pair is generated by the authentication server  4  in step S 212  of  FIG. 2B . However, during the registration procedure, the asymmetric key pair may be optionally generated by the client device  2  rather than the authentication server  4 . 
       FIGS. 2A and 2C  illustrate a variation of the registration procedure, which differs from the above registration procedure in that the asymmetric key pair is to be generated by the client device  2  and which includes the same steps S 201 -S 209 . The following describes in detail the remaining steps of the variation of the registration procedure shown in  FIG. 2C . 
     Following step S 209 , in step  210 ′, in response to receipt of the authentication code from the network server  1 , the client device  2  executes the authentication application  22  to generate the asymmetric key pair including the public key  312  and the private key, and the hardware scanning data that is associated with the identification codes of the hardware components of the client device  2 , to divide the private key into the first private key portion and the second private key portion  315 , and to send the authentication code received thereby, the hardware scanning data, the public key  312 , and the second private key portion  315  generated thereby to the authentication server  4  via the fifth communication channel  405 . 
     In step S 211 ′, upon receipt of the public key  312 , the second private key portion  315 , the hardware scanning data and the authentication code from the client device  2 , the authentication server  4  verifies whether the authentication code received thereby matches the authentication code generated in step S 208 . If the result is affirmative, the flow goes to step S 212 ′. Otherwise, similar to step S 213  of  FIG. 2B , the authentication server  4  sends an error message to the client device  2  for displaying on the display unit of the client device  2  (step S 213 ′). 
     In step S 212 ′, the authentication server  4  stores the second private key portion  315 , and the hardware scanning data received thereby as the reference hardware identification data  41  that is associated with the UID  311  of the end user  5  and that is used to verify the identity of the client device  2 , sends to the client device  2  via the fifth communication channel  405  the certificate reference  32  included in the authentication registration request received thereby at the beginning of step S 208 , and sends the public key  312  to the verification server  3  via the fourth communication channel  404  (step S 212 ′). 
     Following step S 212 ′, in step S 214 ′, upon receipt of the certificate reference  32  from the authentication server  4 , through the executed authentication application  22 , the client device  2  generates the PIS code through an input operation of the user input interface by the end user  5 , encrypts the first private key portion with the PIN code generated thereby to generate the reference first private key portion  23 , and stores the reference first private key portion  23  and the certificate reference  32  in the storage unit. 
     In step S 215 ′, upon receipt of the public key  312  from the authentication server  4 , the verification server  3  stores the public key  312  received thereby in the database unit. 
     Referring to  FIGS. 1, 2A, 3B and 3C , the system  100  is configured to implement a procedure of an electronic transaction between the end user  5  and the network server  1  in accordance with the network authentication method of the embodiment. The procedure of the electronic transaction illustrates identity verification, signature verification and data verification, and includes the following steps. 
     In step S 301 , upon execution of the service application  21  on the client device  2 , the end user  5  inputs user login data using the user input interface (not shown in the drawings) of the client device  2  at a website provided by the network server  1 . The user login data is then sent from the client device  2  to the network server  1  via the first communication channel  401 . In this embodiment, the user login data includes the UID  311  of the end user  5 , and the password. 
     In step S 302 , upon receipt of the user login data from the client device  2 , the network server  1  determines whether the user login data thus received is correct. If the result is affirmative, the network server  1  sends a successful login message to the client device  2  via the first communication channel  401  (step S 303 ). Otherwise, the network server  1  sends an error message to the client device  2  for displaying on the display unit of the client device  2  (step S 300 ). 
     Following step S 303 , in step S 304 , through the executed service application  21 , the client device  2  sends a transaction message associated with the electronic transaction to the network server  1  via the first communication channel  401 . 
     In step S 305 , upon receipt of the transaction message from the client device  2 , the network server  1  processes the transaction message thus received to generate transaction data that is to be confirmed and signed by the end user  5 . Then, the network server  1  sends an authentication request for the electronic transaction to the authentication server  4  via the third communication channel  403 . In this embodiment, the authentication request includes the UID  311  of the end user  5  and the transaction data. 
     In step S 306 , upon receipt of the authentication request from the network server  1 , the authentication server  4  generates a one-time message identification (MID) that corresponds uniquely to the authentication request thus received, and sends the MID to the network server  1  via the third communication channel  403 . 
     In step S 307 , the network server  1  transmits the MID from the authentication server  4  to the client device  2  via the first communication channel  401 . 
     In step S 308 , the client device  2  executes, in response to receipt of the MID from the network server  1 , the authentication application  22  to generate hardware scanning data that is associated with the identification codes of the hardware components of the client device  2  and to send the MID received thereby and the hardware scanning data generated thereby to the authentication server  4  via the fifth communication channel  405 . 
     In step S 309 , upon receipt of the MID and the hardware scanning data from the client device  2 , the authentication server  4  verifies whether the hardware scanning data received thereby matches the reference hardware identification data stored therein during the registration procedure (i.e., to verify the identity of the client device  2 ). If the result is affirmative (i.e., the identity of the client device  2  is successfully verified), the authentication server  4  sends the second private key portion  315  and a signature request for the transaction data to the client device  2  via the fifth communication channel  405  (step S 310 ). The signature request includes the transaction data that is received by the authentication server  4  in step S 306 . Otherwise, the authentication server  4  sends an error message to the client device  2  for displaying on the display unit of the client device  2  (step S 311 ). 
     Following step S 310 , in step S 312 , upon receipt of the second private key portion  315  and the signature request from the authentication server  4 , the client device  2  first displays the transaction data on the display unit for viewing by the end user  5  so that the end user  5  is able to confirm the correctness of the transaction data displayed on the display unit of the client device  2 . Subsequently, after confirmation, the client device  2 , through the executed authentication application  22 , generates a user input code through an input operation of the end user  5  using the user input interface, decrypts the reference first private key portion  23  stored in the storage unit with the user input code to obtain a current key portion, combines the current key portion and the second private key portion  315  received thereby into a current key, and generates a digital signature for the transaction data using the current key and the transaction data. It is noted that, in this case, the reference first private key portion  23  can be successfully decrypted using the user input code to obtain the first private key portion to serve as the current key portion when the user input code is identical to the PIN code. Then, the client device  2  sends, in response to the signature request, the certificate reference  32  stored therein, and the digital signature generated thereby and associated, with the certificate reference  32 , to the authentication server  4  via the fifth communication channel  405 . 
     In step S 313 , upon receipt of a digital signature and a certificate reference  32  via the communication network  400 , the authentication server  4  sends a verification request for the digital signature thus received to the verification server  3  via the fourth communication channel  404 . In this embodiment, the verification request for the digital signature includes the digital signature and the certificate reference  32 . 
     In step S 314 , in response to receipt of the verification request from the authentication server  4 , the verification server  3  verifies, based on the public key  312  corresponding to the certificate  31  to which the certification reference  32  is uniquely mapped, whether or not the digital signature included in the verification request thus received is signed with the private key. If the result is affirmative (i.e., the user input code is identical to the PIN code), the verification server  3  successfully decrypts the digital signature with the public key  312  to thus obtain from the decrypted digital signature the transaction data that is determined to be associated with the end user  5  and that has been confirmed by the end user  5 , and notifies the authentication server  4  of successful digital signature verification (step  315 ). Otherwise, the verification server  3  notifies the authentication server  4  of failed digital signature verification (step  316 ). 
     Following step S 315 , in step S 317 , upon receipt of the notification of successful digital signature verification from the verification server  3 , the authentication server  4  notifies the client device  2  of completion of digital signature verification. 
     Following step S 316 , in step S 318 , upon receipt of the notification of failed digital signature verification from the verification server  3 , the authentication server  4  increases a failure trial count of a failure counter (not shown in the drawings) associated with the authentication request for the electronic transaction by one, and determines whether the count value of the failure trial count is less than a predetermined threshold value, which is, for example, equal to 3. If the result is affirmative, the flow goes back to step S 310  to permit the end user  5  to enter again another user input code for generation of another digital signature. In this case, the signature request for the transaction data sent by the authentication server  4  in step S 310  further includes notification of PIN error. Otherwise, the flow goes back to step S 311 . 
     Following step S 317 , in step S 319 , upon receipt of the notification of completion of digital signature verification from the authentication server  4 , the client device  2  sends, through the executed, service application  21 , the certificate reference  32  stored therein to the network server  1  via the first communication channel  401 . 
     In step S 320 , upon receipt of a certificate reference  32  via the communication network  400 , the network server  1  sends a verification request for the transaction data to the verification server  3  via the second communication channel  402 . In this embodiment, the verification request includes the transaction data and the certificate reference  32  thus received. 
     In step S 321 , in response to receipt of the verification request from the network server  1 , the verification server  3  determines whether the transaction data from the network server  1  matches the transaction data obtained thereby in step S 315  and actually confirmed by the end user  5 . If the result is affirmative (i.e., it is confirmed that during transmission from the client device  2  to the network, server  1 , the transaction message has not been tampered with), the verification server  3  notifies the network server  1  of successful transaction data verification (step S 322 ). Otherwise, the verification server  3  sends an error message to the network server  1  (step S 323 ). 
     Following step S 322 , in step S 324 , in response to receipt of the notification of successful transaction data verification from the verification server  3 , the network server  1  notifies the authentication server  4  of successful transaction data verification. 
     In step S 325 , upon receipt of the notification of successful transaction data verification from the network server  1 , the authentication server  4  notifies the network server  1  of successful authentication of the electronic transaction, and clears the failure trial count of the failure counter. Finally, upon receipt, of notification of successful authentication of the electronic transaction from the authentication server  4 , the network server  1  processes the transaction data generated in step S 305  to perform the electronic transaction (step S 326 ). 
     Following step S 323 , in step  3327 , upon receipt of the error message, the network server  1  sends an error message to the client device  2 , which then notifies the end user  5  that the transaction has been cancelled (step S 327 ). 
     The following are some of the advantages attributed to the network authentication method of the disclosure: 
     1. Since the private key is divided in the registration procedure into the first private key portion, which is not stored in any one of the network server  1 , the client device  2 , the verification server  3  and the authentication server  4 , and the second private key portion  315 , which is stored merely in the authentication server  4 , and since the client device  2  merely stores the reference first private key portion  23  associated with but not same as the first private key portion in the registration procedure, the attacker can hardly obtain the complete private key, thereby ensuring effective electronic signature. 
     2. Only the certificate reference  32 , instead of the complete certificate  31 , is transmitted within the communication network  400 . In other words, after the public key  312  is stored in the verification server  3 , the public key  312  is not outputted by the verification server  3  and is not transported within the communication network  400 . Therefore, the attacker cannot steal the certificate  31  stored in the verification server  3  via the communication network  400 , thereby ensuring effective digital signature authentication. 
     3. After successful digital signature authentication, the transaction data of the electronic transaction obtained by the network server  1  is further verified by the verification server  3 , thereby effectively preventing the transaction message (transaction data) from being tampered with during transmission from the client device  2  to the network server  1 . 
     4. In addition to the service application  21 , the authentication application  22  is stored in the client device  2  and is executed to generate hardware scanning data associated with the hardware components of the client device  2  for subsequent use in authenticating the identity of the client device  2 . 
     In sum, due to the above advantages, the network authentication method of this disclosure can secure electronic transactions without the need for the additional identity verification device(s) in the prior art. 
     While the disclosure has been described in connection with what is considered the most practical embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.