Patent Publication Number: US-6983381-B2

Title: Methods for pre-authentication of users using one-time passwords

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present invention disclosure claims priority to Provisional U.S. Patent Application No. 60/262,875, filed Jan. 17, 2001, entitled Method and Apparatus for Pre-Authentication of Users Using One-Time Passwords. This application is herein by incorporated by reference for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to secure computer network access. In particular, the present invention relates to methods and apparatus for issuing and using one-time passwords for secure computer networks. 
     Secure remote access to computer networks requires the end user to be authenticated before the end user is granted access to the network. In current secure remote access systems, the end user is authenticated using a variety of methods. In one method, when the end user accesses a remote server, the end user is prompted for a combination of user name or login name, password or personal identification number (“PIN”), and the like. Upon verification that the user login name and PIN are registered, the end-user is granted access to a computer network. 
     Drawbacks to this scheme include that once the user name and password is compromised or stolen, unauthorized access to the computer system can easily occur. Another drawback includes that simple password guessing strategies can be used to guess a password. 
     Another method for restricting user access to a computer system has been through the use of electronic “key cards” or “tokens.” In such solutions, users are typically issued a physical hardware device or software that allows users to enter data therein. In response to such user data, these devices output passwords, or the like that are subsequently used for a login attempt. 
     Drawbacks to such devices include that it is very easy to misplace or lose such hardware devices. Another drawback is that kids, pets, or the like may tamper with such “toys” to render them inoperative. Yet another drawback is that in such systems, system administrators need to manually pre-register the key cards, before the key cards will work. Still another drawback is that if the hardware device is stolen, or the like, the thief will then possess the requisite electronic identification to access the computer network. 
     Another drawback is that such systems rely on precise time synchronization between such “keycards” or “tokens” and the server machine. This is often difficult to perform and difficult to maintain because of clock drifts in the various devices. 
     Thus in light of the above, what is needed in the industry are improved methods and apparatus for issuing and using one-time passwords for computer networks, while reducing the drawbacks discussed above. 
     SUMMARY OF THE INVENTION 
     The present invention relates to methods and apparatus for securely obtaining and using one-time passwords. Embodiments of the present invention may be applied to firewalls, VPN Gateways, Electronic Mail servers, web servers, database systems, application servers, wireless applications, secure distributed services access, embedded applications, and the like. Embodiments may advantageously be applied to currently deployed computer systems that include a firewall, a VPN Gateway or the like, without modification thereof. 
     Embodiments include methods and apparatus wherein a verification server (authentication server) sends a one-time password to a user as a challenge via an external server. The communication between the verification server, external server, and the users client system uses “strong” forms of encryption itself, such as IPSec, SSL, S-HTTP or the like. The verification server then receives a challenge response. In one embodiment, the challenge response includes a digital signature. In one embodiment, the challenge response also includes a digital certificate including the public key in encrypted form. In other embodiments, other forms of encryption other than using key pairs may also be used. 
     Once the verification (authentication) server verifies the user, via the digital signature and digital certificate, the verification server pre-authenticates or activates the onetime password. The user may then sign-on using the password-based security system using a user identification and the one-time password. Because the one-time password has been pre-authenticated or activated by the verification server, the password-based security system will approve the connection. As described in the attached documents, time limits may be set within the verification server such that if a login attempt is not made within a period of time after activating the one-time password, the one-time password is unauthorized, deleted, inactivated, or the like. 
     According to one aspect of the invention, a server can be used to implement a method for obtaining and using pre-authorized passwords. The method may include receiving at the server a challenge from an authentication server via a first secure communications channel, the challenge comprising a random password that is inactive, and communicating the challenge from the server to a client computer via a second secure communications channel. The communications channels can comprise physically distinct communication paths, or can be logical channels in a single communication path. The technique also includes receiving at the server a challenge response from the client computer via the second secure communications channel. A challenge response includes a digital certificate and a digital signature. The digital certificate typically includes a public key in an encrypted form. The public key and the private key form a key pair. Various techniques include communicating the challenge response from the server to the authentication server via the first secure communications channel. The random password is activated when the authentication server verifies the challenge response. Activation of the password in the authentication server allows a user to successfully login to a password-based security system coupled to the authentication server using that password. 
     According to another aspect of the invention, a method for a client computer is disclosed. One technique includes receiving a challenge from a authentication server via a first secure communications channel, the challenge comprising a password that is inactive, receiving a user PIN, and recovering a private key in response to the user PIN. The technique may also include sending digital certificate to the authentication server via an external server, the digital certificate comprising a public key in a protected form, and sending a digital signature to the authentication server via the external server. Thereafter, the process may include sending a user login and the password to a password-based security system coupled to the authentication server. The authentication server may verify the digital signature and then activate the password. 
     According to another aspect of the invention, a server can be used to implement a method of providing one-time passwords. One technique may include receiving a request for a one-time password from a client computer, and determining a one-time password, the one-time password being inactive. The method may also include communicating the one-time password to the client computer, and receiving user identification data from a user at the client computer. Authenticating the user in response to the user identification data, and activating the one-time password when the user is authenticated are steps also provided in various embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  illustrates a block diagram according to an embodiment of the present invention; 
         FIG. 2  is a block diagram of a typical external server according to an embodiment of the present invention; 
         FIG. 3  illustrates a more detailed embodiment of the present invention; 
         FIGS. 4A–D  illustrate block diagrams of a flow chart according to an embodiment of the present invention; and 
         FIGS. 5A  and B illustrate other embodiments of the present invention. 
     
    
    
     DESCRIPTION OF THE SPECIFIC EMBODIMENTS 
     The attached documents describe embodiments of the present invention. More specifically, the documents describe embodiments where “strong” forms of encryption, such as public key cryptography, are used to obtain one-time passwords. Such passwords may be advantageously used by conventional password-based security systems, or the like. 
       FIG. 1  illustrates a block diagram according to an embodiment of the present invention.  FIG. 1  illustrates a external server  100 , a private computer network  110 , a private server  120 , and plurality of client systems  130 – 150 . As illustrated, such systems may be coupled to each other via a computer network  160 . 
     In the present embodiment, computer network  160  is the Internet. In alternative embodiments of the present invention, computer network  160  may be any computer network, such as an intranet, a wireless network, a local area network, an internet, and the like. Computer network  160  provides data communication among client systems  130 – 150 , external server  100 , and private company network  110 . Data communication may include transfer of HTML based data, textual data, binary data, form submissions, plug-in programs or viewers, applets, audio data, video data, encrypted data, and the like. Although computer network  160  is illustrated as a single entity, as is the case with the Internet, it should be understood that computer network  160  may actually be a network of individual routers and computer servers. 
     In this example, external server  100 , private computer network  110 , and client system  130 – 150  may include network connections that may have varying bandwidth characteristics, such as T 1  connections, 384 kilobits per second (kbps), 56 kbps connections, 14.4 kbps, and the like. 
     In the present embodiment, client systems  130 ,  140 , and  150  may embodied as typical desktop personal computers such as those available from companies such as HP, Compaq, IBM, and the like. In alternative embodiments, other personal computers such as those available from Apple or Dell, may also be used. Alternatively, client systems  130 – 150  may be embodied as notebook computers, television set top boxes, (e.g. WebTV™), game consoles (e.g. PlayStation2™), network computers, or other types of units incorporating processors, microcontrollers, ASICs, and the like. In other embodiments, client systems  130 – 150  may be embodied as PDAs or other portable computing platforms operating upon PalmOS, WindowsCE, and the like, or embodied as wireless devices using cellular technology, CDMA, TDMA, and other technologies, and using wireless application protocols such as WAP. In still other examples, client systems  130 – 150  may be embodied within kiosks, wrist watches, pocket or portable displays or terminals, wearable computers, retinal implants, surveillance equipment, kitchen appliances, and the like. 
     In the present embodiment, communications among external server  100 , private computer network  110 , private server  120 , and client systems  130 – 150  are performed using application software that supports secure-IPSec, HTTP (S-HTTP), TCP/IP, Secure Socket Layer (SSL) protocols, RTP/RTSP protocols, or other protocols, such as UDP. These communication protocols are well known, thus no description is given herein. Additionally, client systems  130 – 150  store and use encrypted public/private key pairs associated with authorized users, as will be described below. 
     The diagram in  FIG. 1  is merely an illustration which should not limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. 
       FIG. 2  is a block diagram of a typical external server  200  according to an embodiment of the present invention. External server  200  typically includes a monitor  210 , a computer  220 , a keyboard  230 , a graphical input device  240 , a network interface  250 , and the like. 
     In the present embodiment, graphical input device  240  is typically embodied as a computer mouse, a trackball, a track pad, wireless remote, and the like. Graphical input devices typically allow the users to graphically select objects, icons, text and the like output on monitor  210  in combination with a cursor. 
     Embodiments of network interface  250  include an Ethernet card, a modem (telephone, satellite, cable, ISDN), (asynchronous) digital subscriber line (DSL) units, and the like. Network interface  250  is coupled to a typical network as shown. 
     Computer  220  includes familiar computer components such as a processor  260 , and memory storage devices, such as a random access memory (RAM)  270 , a disk drive  280 , and a system bus  290  interconnecting the above components. 
     In one embodiment, computer  220  is a PC compatible computer having an x 86  based microprocessor, such as an Athlon™ microprocessor from Advanced Micro Devices, Inc. running WindowsNT™ operating system from Microsoft Corporation. 
     RAM  270  and disk drive  280  are examples of tangible media for storage of data, audio message files, computer programs, embodiments of the herein described invention, binary files, encrypted data, applet interpreters or compilers, virtual machines, and the like. Other types of tangible media include floppy disks, removable hard disks, optical storage media such as CD-ROMS and bar codes, semiconductor memories such as flash memories, read-only-memories (ROMS), and battery-backed volatile memories, and the like. In embodiments of the present invention such as set top boxes, mass storage, such as disk drive  280 , and the like may be dispensed with. 
     In the present embodiment, external server  200  also includes software that enables it to send and receive data to and from client systems  130 – 140  and private computer network  110  using communications protocols including, HTTP, S-HTTP, TCP/IP, IPSec, SSL, RTP/RTSP and the like. In alternative embodiments of the present invention, other software and transfer and communication protocols may also be used, for example IPX, UDP or the like. 
       FIG. 2  is representative of but one type of system for embodying the present invention. It will be readily apparent to one of ordinary skill in the art that many other hardware and software configurations are suitable for use with the present invention. For example, other types of processors are contemplated, such as the Pentium™-class or Celeron™-class microprocessors from Intel Corporation, PowerPC™ G3 or G4 microprocessors from Motorola, Inc., Crusoe™ processors from Transmeta, Inc. and the like. Further, other types of operating systems are contemplated in alternative embodiments including Solaris, LINUX, UNIX, MAC OS X from Apple Computer Corporation, BeOS™, and the like. Embodiments of private server  120  and client systems  130 – 150  may be configured similar to that shown in  FIG. 2 . 
       FIG. 3  illustrates a more detailed embodiment of the present invention. In particular,  FIG. 3  includes a client system  300 , an external server  310 , and a private network  320 . Private network  320  includes a firewall (or VPN) server  340 , an authentication server  350 , and a private server  360  coupled via a router  330 . 
     In this embodiment, client system  300  is coupled to both external server  310  and private network  320  often at different times, as will be described in greater detail below. As shown, firewall server  340  within private network  320  provides an interface for client system  300 . In this embodiment, firewall server  340  in combination with authentication server  350  are used to authenticate the user at client system  300 . Further, the combination is typically used to prevent unauthorized access to private server  360 . 
       FIGS. 4A–D  illustrate block diagrams of a flow chart according to an embodiment of the present invention with reference to the elements shown in  FIG. 3 . 
     Initially, a user receives or establishes an asymmetric encryption key pair, step  400 . For example, the user may have been assigned or may have obtained a private key and a public key. The concepts of key pairs are well known in the industry. Next, the user obtains a digital certificate from a certificate authority (CA) or the like, step  410 . In one embodiment, the digital certificate comprises a user&#39;s public key encrypted with the CA&#39;s “domain key” (typically a symmetric key). The user&#39;s private key and digital certificate are then typically stored in a “key wallet” on the user&#39;s computer, step  420 . 
     In one embodiment of the present invention, the key wallet is a software application that securely stores the private key and the digital certificate. In one embodiment, to retrieve the private key and digital certificate from the key wallet, the user has to first enter one or more user name and a personal identification number (PIN), or the like. In one case, when the user name/PIN combination is correct, the key and digital certificate associated with the user is returned. 
     In other embodiments, the key wallet may return keys and certificates that are not associated with the user. In such an example, the keys and digital certificates appear to be valid, but they are inoperative to authenticate the user. Such embodiments include Arcot Systems brand “Cryptographic Camouflage” key protection system as described in the U.S. application Ser. No. 08/996,758, titled Method and Apparatus for Cryptographically Camouflaged Cryptographic Key Storage, Certification and Use, filed Dec. 23, 1997, and assigned to the same assignee. This application is incorporated by reference for all purposes. 
     In other embodiments, the key wallet may require other types of data than user names/passwords, for example, biometric data may be used. Examples of biometric data include fingerprints, retina scans, spoken text, execution of physical tasks, and the like. 
     In this embodiment, the user&#39;s computer may include additional software that may provide automatic use of the private key and digital certificate. One such embodiment of the additional software is called Arcot for Virtual Private Networks presently available from Arcot Systems, Inc. In an embodiment of the present invention, the additional software is downloaded from a computer network, or installed via physical media (CD-ROM), or the like, step  430 . 
     Referring to  FIG. 3 , the user at client system  300  next wants to access private server  360 , step  440 . The user enters their user name, PIN, biometric data, and the like to authenticate themselves, step  450 . If such data are valid, i.e. the user is authenticated, step  460 , the key wallet decrypts data and retrieves the private key and the digital certificate associated with the user, step  470 . If the data are invalid, an inoperative key and certificate may be generated as discussed in the above U.S. Patent Application, step  480 . 
     In this example, the application software in client system  300  contacts external server  310  to request a one-time password (or any other identification code), step  490 . The connection between client system  300  and external server  310  may be via the Internet, via a direct dial-up connection, or any other means including wireless. This connection is typically a secure connection including encryption of data between client system  300  and external server  310 , such as IPSec, S-HTTP, SSL, or the like. 
     In response to the request, external server  310  contacts an authentication server  350  and requests a one-time password, step  500 . The connection between external server  310  and authentication server  350  may be via the Internet, via a direct dial-up connection, or any other means including wireless. This connection is also typically a secure connection including strong forms of encryption of data between client system  300  and external server  310 , such as IPSec, S-HTTP, SSL, or the like. In one embodiment, communications between external server  310  and authentication server  350  may be direct, or indirect, for example via firewall server  340 . 
     Authentication server  350  next generates a one-time password (also known as a pre-authorized password) in response to the request, step  510 . In this embodiment, the one-time password is not activated, i.e. authentication server  350  will not allow access to private server  360  based upon the one-time password. 
     The one-time password is then communicated to external server  310 , step  520 , and external server  310  then communicates it to client system  300 , step  530 . This one-time password may be considered a “challenge” from authentication server  350  to client system  300 . 
     In the present embodiment, the additional software in client system  300  receives the one-time password, and creates a digital signature, step  540 . In one embodiment, the digital signature is a virtually unforgable transformation of the one-time password with the private key. In other embodiments, other conventional methods for forming digital signatures may be used such as using hashing. 
     Next, client system  300  sends the digital signature and digital certificate to external server  310 , step  550 . As above, the transfer of data typically is via a secure communications channel. The digital signature and digital certificate are then communicated to authentication server  350 , step  560 . Again, strong forms of encryption may be used to protect the communication. This response from client system  300  may be considered a “challenge response” to authentication server  350 . 
     In this embodiment, authentication server  350  receives the digital certificate, and decrypts it using the Certification Authority&#39;s (CA&#39;s) domain key, step  570 . In one embodiment, the authentication server stores the domain key securely on the authentication server machine. The domain key can be stored on the authentication server in a password-protected file, a hardware token, or the like. In an alternative embodiment, authentication server  350  accesses the appropriate CA that issued the digital certificate for the domain key. In either embodiment, authentication server  350  then uses the CA&#39;s domain key and uses it to decrypt the digital certificate. In response to the decryption, the public key of the user is recovered. 
     The public key is used to verify the digital signature to confirm that only the user with the corresponding private key could have possible produced the digital signature, step  580 . This step is a standard operation supported by algorithms such as RSA. 
     In this embodiment, the verification confirms the identity of the user who created the signature, step  590 . If the digital signature is verified, the challenge is activated for that specific user and the challenge becomes the one-time-password within authentication server  350 , step  600 . If they do not match, the one-time password remains inactive, step  610 . 
     The present method therefore does not require authentication server  350  or external server  310  to pre-register a hardware “key” or “token” as was discussed in the background. Further, it does not require precise synchronization between devices, as was also discussed in the background. 
     In one embodiment, notification of the success or failure of the digital signature match, such as an error message is sent back to client system  300 . Further, if the digital signature is not verified, the process may alternatively return back to step  450 . 
     In one embodiment, the challenge provided by authentication server  250  is not the one-time password, instead, the challenge may be any random or pseudo random message, characters, or the like. The challenge is digitally signed and sent back to authentication server  350  as described above. If the user is authenticated, authentication server  350  may then send an activated one-time password to client system  300  via external server  310  using the same secure communications channels. 
     In either embodiment, after successful authentication, at this stage, client system  300  has an activated one-time password. Next, client system  300  is coupled to network  320 , step  620 . The communications channel is typically encrypted using IPSec, S-HTTP, SSL, or the like. As shown, private network  320  typically includes a firewall server  340  to prevent unauthorized access to private server  360 . 
     In this embodiment, client system  300  transfers authorization data to firewall server  340 , step  630 . In this example, the authorization data may include another user name and password combination, as well as the one-time password received from authentication server  350 . 
     In response, firewall server  340  contacts authentication server  350 , step  640 . In the present embodiment, communications between firewall server  340  and authentication server  350  may be using secure techniques such as Remote Authentication Dial In User Service (RADIUS), TACACS+ or the like. Firewall server  340  then communicates the authorization data and one-time password to authentication server  350 , step  650 . In this embodiment, authentication server  350  determines whether the one-time password is active and the authorization data is correct, step  660 . If matches are made, authentication server  350  notifies the firewall server that access is approved, step  670 , otherwise access is denied, step  680 . 
     If the access is approved, client system  300  is provided access to private server  360 , and the like, step  690 . In one example, after the one-time password has been successfully used, the one-time password is de-activated. In other embodiments, the passwords remain active even after being used by authentication server  350 . Such an embodiment would be a method for providing accesses and assigning passwords to “new” users or giving passwords to users during “initial” visits. 
     In one embodiment of the present invention, many of the steps are hidden from the user and may be automatic. In one example, the user performs step  450  and then simply waits until steps  680  or step  690  are performed. In this example, the steps  620  and  630  are automatically performed for the user. In another embodiment, after step  600 , the secure communications between client system  300  and authentication server  350  is terminated. The user then manually performs steps  620  and  630 . 
       FIGS. 5A  and B illustrate other embodiments of the present invention. In particular,  FIGS. 5A and 5B  illustrate other schemas for communication among a client system, an external server, and authentication server. 
     In one embodiment, as illustrated in  FIG. 5A , a client system  400  does not contact external server  310  directly. Instead, as shown, a filtering module  470  is installed into firewall server  440 . When filtering module  470  detects a request from client system  400  for a one-time password, filtering module  470  re-directs the request to external server  410 . 
     In an embodiment illustrated in  FIG. 5B , external server  310  does not directly contact authentication server  350 . Instead, as shown, communications are channeled through firewall server  440 . 
     Further embodiments can be envisioned to one of ordinary skill in the art. For example, in one embodiment, the password-based security system may be integrated into a firewall, VPN or the like. In another embodiment the external server communicates with the verification server without passing through a firewall, or the like. In another case, the external server and the verification server are both behind a firewall, VPN, or the like. In yet another embodiment, the verification server and the firewall may be integrated into one server. 
     In one embodiment of the present invention, authentication server  350  may send a one-time password and a challenge. In such an embodiment, the challenge may be digitally signed and returned to authentication server  350  along with the digital certificate for verification purposes. If the user is verified, authentication server  350  activates the one-time password. Thus, in this embodiment, the one-time password need not be digitally signed as described in the above disclosure. 
     In one embodiment of the present invention, activation of the one-time passwords may be time limited. Thus although the one-time password and the authorization data may be correct, authentication server  350  may still deny access to the network. As an example, when authentication server issues a one-time password, it sets a maximum period of time that the one-time password is active, e.g. 5 minutes. Accordingly, if the user at client system  300  tries to gain access to private network  320  the next day, their access would be denied. 
     In still another embodiment, the one-time passwords may be active for only a limited number of login attempts. Thus although the one-time password and the authorization data may be correct, authentication server  350  may still deny access to the network. As an example, when authentication server issues a one-time password, it sets a maximum number of tries, e.g. 3 tries. Accordingly, if the user at client system  300  tries to gain access to private network  320  using the incorrect user name and password, but the correct one-time password, after the third try, the one-time password is deactivated. By providing such use-limited one-time passwords, it is believed the risks of network access compromise are reduced. 
     In light of the present patent application disclosure, embodiments of the present invention may be applied to financial transactions, such as credit card transaction systems, or the like. For example, one-time credit card numbers, one-time debit card numbers, or the like may be enabled in much the same manner as described above for one-time passwords. Accordingly, a client may first make a request for a one-time credit card number. In response, a credit-card authentication server may issue a challenge in the form of a one-time credit card number via an external server. The client signs the one-time credit card number with the user&#39;s private key and transmits the signed card number with the user&#39;s digital certificate. If the authentication server verifies that the signature and certificate, the one-time credit card number is activated. Later, when the user decides to pay for a product, service, or the like, the user submits the one-time credit card number. If verified above, the financial transaction is completed using the one-time credit card number. In other embodiments, other financial transaction data may be provided by the authentication server, for example, one-time bank account number, brokerage account number, telephone access card, and the like. 
     In one embodiment of the present invention, the client system may include a level of key wallet password checking. In the embodiment illustrated above, if a user enters an incorrect key wallet password, an inoperative private key and digital certificate are retrieved from the key wallet in step  480 . In this embodiment, for an incorrect key wallet password, the key wallet application may report that the password is incorrect, and the method goes back to step  450 . Such a comparison may be accomplished by using a hash or partial hash of the user&#39;s key wallet password, or the like. In different embodiments, the key wallet application may report incorrect passwords half the time, one-quarter the time, or any other frequency desired. Further, the key wallet application may report incorrect passwords that only include typographic error derivations of the password, or the like. 
     In other embodiments of the present invention, combinations or subcombinations of the above-disclosed invention can be advantageously made. The block diagrams of the architecture and flowcharts are grouped for ease of understanding. However it should be understood that combinations of blocks, additions of new blocks, re-arrangement of blocks, and the like are contemplated in alternative embodiments of the present invention. 
     The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the claims.