Abstract:
A method of maintaining ongoing authentication of a user of an application without the need to enter and re-enter a username and a corresponding password for each session initiated between a client side application residing on a client side platform and a server; and wherein the password is not stored on the server; the method comprising utilising an unbroken chain of one-time pass codes; each pass code in the chain being unique to the username and client side application; each pass code renewed periodically and preferably at least once during each said session.

Description:
[0001]    The present invention relates to a persistent authentication system incorporating one time pass codes and more particularly, but not exclusively such a system which does not require a user of the system to enter and re-enter a username and a corresponding password for a user session initiated by the user. 
       BACKGROUND 
       [0002]    The use of usernames and passwords is well known in the art. A growing problem exists where the server side storage of passwords is becoming more prone to attack and the burden on users to use different and secure passwords across multiple web sites has introduced inconvenience, inordinate complication and continuing security exposure. 
         [0003]    Attempts to solve this problem include device hardware fingerprinting or other multi factor authentication such as biometrics. These are used in an attempt to bolster the security and reduce the exposure of problems associated with standard username and password authentication systems. However, typically they only add more steps of complexity and inconvenience to an already burdensome process. 
         [0004]    One example of such an attempt is U.S. Pat. No. 5,875,296 to IBM the content of which is incorporated herein by cross reference. Its solution is outlined in claim  1  thereof which reads: 
         [0005]    A method of authenticating a client to a Web server connectable to a distributed file system of a distributed computing environment, the distributed computing environment including a security service for returning a credential to a user authenticated to access the distributed file system, comprising the steps of:
       responsive to receipt by the Web server of a user id and password from the client, executing a login protocol with the security service and storing a credential resulting therefrom;   returning to the client a persistent client state object having an identifier therein; and   having the client use the persistent client state object including the identifier in lieu of a user id and password to obtain subsequent access to Web documents in the distributed file system.
 
This arrangement can be interpreted as utilising a “cookie” as the persistent client state object. This arrangement suffers from significant security issues.
       
 
         [0009]    Further prior art examples (all of which are included by cross reference) include: 
         [0010]    U.S. Pat. No. 8,447,977 Canon K K whose main claim reads: 
         [0011]    A method of authenticating a device with a server over a network, the method comprising the steps of:
       establishing, by the device, a secure connection with the server;   communicating, by the device, identification information of the device to the server, wherein the identification information uniquely identifies the device to the server and is pre-stored in the device;   determining, by the server, the credibility of the device using the identification information communicated by the device; and   in a case where the server determines that the device is credible:   creating, by the server, a first authentication token for the device, the first authentication token indicating that the device is credible;   storing, by the server, the first authentication token;   transferring, by the server, the first authentication token to the device using the secure connection; and   storing, by the device, the first authentication token;   wherein the method further comprises the steps of:   establishing, by the device, a secure re-connection with the server; and   authenticating, by the server and over the secure re-connection, the device using the first authentication token stored by the device.       
 
         [0023]    U.S. Pat. No. 6,668,322 Sun MicroSystems whose Main Claim Reads 
         [0024]    A session credential for use in a security architecture controlling access to one or more information resources, the session credential comprising:
       a principal identifier uniquely identifying a principal; and   an encoding of authorization accorded by the security architecture after prior authentication of a login credential corresponding to the principal,   the principal identifier and authorization encoding being cryptographically secured and allowing the security architecture to evaluate sufficiency of the authorization for access to the one or more information resources without re-authentication of the login credentials.       
 
         [0028]    U.S. Pat. No. 6,421,768 First Data whose Main Claim Reads 
         [0029]    A method for transferable authentication, by which a user accessing a first computer can be authenticated to a second computer remote from said first computer, without necessarily requiring the user to explicitly identify himself to said second computer, comprising the steps of:
       at a user&#39;s computer, accessing said first computer;   authenticating said user to said first computer;   receiving from said first computer a cookie including said first computer&#39;s digital voucher of a user characteristic, said voucher being cryptographically assured by said first computer, said user characteristic being encrypted and incorporated into said digital voucher by said first computer using a client side public key confidential to said first computer and said second computer but unknown to said user, said client side public key being cryptographically assured using an asymmetric key of at least one of said first computer and said second computer;   transmitting said cryptographically assured client side public key to said second computer via said user&#39;s computer; and   sending at least a portion of said cookie, including said voucher, to said second computer configured to:   authenticate said voucher without necessarily requiring said user to explicitly identify himself to said second computer;   extract said user characteristic from said voucher; and   perform an action based on said user characteristic.       
 
         [0038]    As stated above cookies have particular security issues and have ongoing adoption issues these days. 
         [0039]    Also disclosed are the following which disclose alternative ways of seeking to secure systems without the use of repetitive password entry and explicit communication of the password from one machine to another. These systems can be more complex including the use of a third party machine to perform verification/authentication. 
         [0040]    U.S. Pat. No. 4,578,531 AT&amp;T 
         [0041]    U.S. Pat. No. 6,134,592 Netscape 
         [0042]    U.S. Pat. No. 6,205,480 Computer Assoc 
         [0043]    U.S. Pat. No. 7,523,490 Microsoft 
         [0044]    U.S.20110320820 IBM 
         [0045]    U.S.20130219472 A1 QSAN 
         [0046]    Embodiments of the present invention are designed to address these issues. 
         [0047]    Notes 
         [0048]    The term “comprising” (and grammatical variations thereof) is used in this specification in the inclusive sense of “having” or “including”, and not in the exclusive sense of “consisting only of”. 
         [0049]    The above discussion of the prior art in the Background of the invention, is not an admission that any information discussed therein is citable prior art or part of the common general knowledge of persons skilled in the art in any country. 
       BRIEF DESCRIPTION OF INVENTION 
       [0050]    Broadly, the concept encapsulated in embodiments of the present invention is to rely on two pieces of information for a persistent authentication process and corresponding system and apparatus: 
         [0051]    In a preferred, detailed form, a new key pair is generated by the client and passed to the server for each session. Communication for a subsequent session is enabled only if there is a match between this server stored public key and the public key on the client matched to that user (user ID). 
         [0052]    Broadly, stated another way, in accordance with a preferred embodiment there is effected an unbroken chain of one-time pass codes to characterise the user when using the client side application which talks to the server. In a particular form the one-time pass codes are actually the public keys of the client generated key pairs. In a further particular preferred form, there is enabled an aspect of renewal whereby the one-time pass codes keep getting replaced at regular intervals (in a preferred form preferably once per connection session at least). 
         [0053]    Accordingly in one broad form of the invention there is provided a method of maintaining ongoing authentication of a user of an application without the need to enter and re-enter a username and a corresponding password for each session initiated between a client side application residing on a client side platform and a server; and wherein the password is not stored on the server; the method comprising utilising an unbroken chain of one-time pass codes; each pass code in the chain being unique to the username and client side application; each pass code renewed periodically and preferably at least once during each said session. 
         [0054]    Preferably the pass code comprises a client side public key which is maintained persistent on both the client side platform and the server until replaced by the next client side public key in the chain of pass codes. 
         [0055]    Preferably the client side public key comprises a public key of a PKI key pair. 
         [0056]    Preferably the corresponding client side private key is not shared with the server. 
         [0057]    In a further broad form of the invention there is disclosed a device including a processor in communication with a memory adapted to execute an application; said device maintaining ongoing authentication of a user of an application executable on the device without the need to enter and re-enter a username and a corresponding password for each session initiated between a client side application residing on a client side platform on the device and a remote server; and wherein the password is not stored on the server; the method comprising utilising an unbroken chain of one-time pass codes; each pass code in the chain being unique to the username and client side application; each pass code renewed at least once during each said session. 
         [0058]    Preferably the pass code comprises a client side public key which is maintained persistent on both the client side platform and the server until replaced by the next client side public key in the chain of pass codes. 
         [0059]    Preferably the client side public key comprises a public key of a PKI key pair. 
         [0060]    Preferably the corresponding client side private key is not shared with the server. 
         [0061]    In a further broad form of the invention there is provided a system including a device having a processor in communication with a memory adapted to execute an application; said device maintaining ongoing authentication of a user of an application executable on the device without the need to enter and re-enter a username and a corresponding password for each session initiated between a client side application residing on a client side platform on the device and a remote server, the system deriving a first and second item of data; said first item of data comprising: 
         [0062]    “Something you have” which in a preferred form is a client side public key, 
         [0063]    The second item of data comprising “Something you know”. 
         [0064]    Preferably said second item of data comprises a user PIN/password which is used to create a private key for any given session. 
         [0065]    Preferably said second item of data comprises any form of personally identifiable information including but not limited to thumb prints or other biometrics which is used to create a private key for any given session. 
         [0066]    Preferably a new key pair is generated by the client and passed to the server for each session and wherein communication for a subsequent session is enabled only if there is a match between this server stored public key and the public key on the client matched to that user (user ID). 
         [0067]    In yet a further broad form of the invention there is provided a platform including at least a processor in communication with a memory which executes code to perform a method of authentication of a user; said method comprising effecting an unbroken chain of one-time pass codes to characterise the user when using a client side application executing on said platform which communicates with a remote server over the Internet. 
         [0068]    Preferably the one-time pass codes are the public key of the client generated key pair. 
         [0069]    In yet a further broad form of the invention there is provided a system for maintaining ongoing authentication of a user of an application without the need to enter and re-enter a username and a corresponding password for each session initiated between a client side application residing on a client side platform and a server, said system utilising a string of one time passcodes which are renewable and wherein renewal is effected by the passcodes being replaced at regular intervals. 
         [0070]    In a preferred form an interval comprises a once per session connection interval. 
     
    
     
       DRAWINGS 
         [0071]      FIG. 1 —Main components of the example embodiment 
           [0072]      FIG. 2 —Control process for an initial use of the example embodiment 
           [0073]      FIG. 3 —Control process for a non initial use of the example embodiment 
           [0074]      FIG. 4 —is a block diagram of a method of construction of a private key according to a further embodiment. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0075]    Broadly, the idea is to rely on two pieces of information for initial and then ongoing authentication: 
         [0076]    In a preferred, detailed form, a new public key is generated by the client and passed to the server for each session. Communication for a subsequent session is enabled only if there is a match between this server stored public key and the public key on the client matched to that user (user ID). 
         [0077]    Broadly, stated another way, in accordance with a preferred embodiment there is effected an unbroken chain of one-time pass codes to characterise the user when using the client side application which talks to the server. In a particular form the one-time pass codes are actually public keys. In a further particular preferred form, there is enabled an aspect of renewal whereby the one-time pass codes keep getting replaced at regular intervals (once per session at least). 
         [0078]    Disclosed is an example embodiment that uses an unbroken chain of one time pass codes as a surrogate for a password in a traditional username and password authentication system. 
         [0079]      FIG. 1  shows the key components of an example embodiment. When a user, using a unique user ID  23 , connects with a server, an encryption and authentication system such as a public key encryption exchange is typically used. 
         [0080]    Typically the user has a client side application  24  that produces a key pair  10  that is used to communicate with the server which uses its own key pair  11 . In the known practice of public key cryptography the clients private key  12  is used with the public key of the server  14  to encrypt a message and the server uses the public key of the client  13  and the private key of the server  15  to decrypt the sent message. 
         [0081]    Once the identity of the sender  10  and receiver  11  has been verified the two parties share a secret password  17  which is used for high speed encryption and decryption of an encrypted message  16 . 
         [0082]    Typically the encrypted message  16  uses a secret password  17  that is only used for the length of the communication session, after which the password  17  is discarded and no longer used. 
         [0083]    In the example embodiment, the above key exchange and encryption process is expanded to include a second key pair set  18  that is generated by the client. This key pair generation  18  is used to uniquely link the current authenticated session with the next authentication system between the client and the server. 
         [0084]    This key pair  18  includes a private key  20  which is stored locally on the client device and a public key  19  which is also stored locally. The stored client public key is also shared with and transferred to the server  25  which then links a stored reference to the unique user ID  21  of the person currently using the client with a stored copy of the client&#39;s public key  22 . 
         [0085]    During subsequent connections between the client and the server, the stored and shared client public key  19 ,  22 , the server&#39;s public key  14  and the stored private key on the client  20  are used as current client side public key pairs and an additional key pair is then generated and stored for the follow on session. 
         [0086]      FIG. 2  discloses the control process of the initial session of the example embodiment. A user uses an application on the client side  30  of the communication to interact with a server  31 . 
         [0087]    Initially the user connects to a server that uses persistent one time keys with unique IDs  32 . Initially the server and the client use a traditional public key encryption session  33  to secure communications between the client  30  and the server  31 . 
         [0088]    Next the user is confirmed as wanting to use persistent one time codes  34  and the users unique ID is captured or retrieved from the user or from storage on the client and sent to the server  35 . Subsequently the server requests that the client generate a public key pair for use in the next session  36 . The client then generates a public key pair  37  which is securely stored at the client for use in the next session  38  and the public key of the key pair is shared with the server  39 . 
         [0089]    The clients public key that is to be used for the next session is stored on the server using the users unique ID  40 . Once this step has been confirmed the existing SSL, TLS or similar connection is used to secure the ongoing communication between the client and the server until the session is terminated or times out  41 . 
         [0090]      FIG. 3  discloses the control process of the non initial sessions of the example embodiment. A user uses an application on the client side  60  of the communication to interact with a server  61 . 
         [0091]    Initially the user connects to a server that uses persistent one time keys with unique ID&#39;s  62 . Initially the server and the client use a traditional public key encryption session  63  to secure communications between the client  60  and the server  61 . 
         [0092]    Next the unique ID is captured or retrieved from the user or from storage on the client  64 . Next the stored client key pair that were stored during the previous session are retrieved using the current users unique user ID  65 . Then the users unique ID and the previously stored client public key are shared with the server  66 . 
         [0093]    The server then searches it&#39;s own user database for the users unique ID and retrieves the previously saved client public key  67  for comparison with the shared client public key from the client  68 . If the two keys do not match the server informs the user and suggests various measures to address the problem  70 . If a match does occur  69 , the server then requests  71  that a second public key pair be generated by the client  72  and the key pair is subsequently stored  73 . Additionally the public key of the key pair just generated  72  is shared with the server for use in the next session  74 . The server then stores the next client public key to be used with the users unique ID  75  and the current key pairs of both the client and the server are used for ongoing communication between the client and the server until the session is terminated or times out  76 . 
         [0094]    The result is a persistent chain of one time codes in the form of client public keys that can be used to establish and perpetuate a secure connection between a client system and a server system over multiple and ongoing sessions. 
       Alternative Embodiments 
       [0095]    The example embodiment uses the generation and linking of a series of client side public keys that are stored on both the client side and the server side as a persistent identifier for the purposes of authentication. An alternative embodiment could use a chain of TLS session keys such as shared AES pass codes as a persistent identifier. In this case each time a shared client side public key is used, a follow on key is generated and stored on both sides for use in the next session. The advantage of using a client side public key as the persistent identifier is that the client side private key is not shared with the server, unlike in the case of a TLS session key, and therefore adds a level of security to the system. 
         [0096]    In the example embodiment the client is used to generate key pairs for the process to use. In an alternative embodiment the server could be used to generate key pairs and share them with the client for use in follow on sessions. 
         [0097]    The example embodiment shares a server stored copy of the next client public key, with a shared copy of the client public key coming from the client during the current session. An alternative embodiment could use any equivalent of the client public key for comparison purposes including but not limited to a checksum or hash of the client public key. 
       Further Embodiment 
       [0098]    With reference to  FIG. 4  and in a particular preferred form an embodiment of the present invention reliant on two pieces of information in accordance with a method of construction of a private key according to a further embodiment. 
         [0099]    “Something you have” which in a preferred form is the client side public key 
         [0100]    “Something you know” which in a preferred form is the user PIN/password which is used to create a private key for any given session. 
         [0101]    In a further enhancement of the example embodiment the private key of the client key pair can be linked to a specific user of the client device to enforce two factor authentication. This is achieved by requiring the user to enter a PIN or other “thing that the user must know” with “a thing the user must have” in this case a required private key of a valid client key pair in a two factor authentication using the example embodiment. 
         [0102]    In this enhancement the private key  100  of the client key pair  101  is broken into two components  102   103 . The first component is a PIN  102  that is chosen by the user to verify their identity in future sessions. This PIN  102  is subtracted from a complete private key  100  to produce a differential key element  103 . The differential key element  103  cannot be used as a successful private key  100  in a client key pair  101  unless the user adds a correct PIN  102  to the correct differential key element  103  in order to produce a useable private key  100  of useable key pair  101 . 
         [0103]    The differential key element can be safely stored  104  on the client device for use in the next session because the element  104  cannot be successfully used without the required PIN  102 . 
         [0104]    In practice the PIN  102  would be requested of the user at the beginning of each session, then added to the differential key element  103  in order to establish successful public key data encryption and decryption. 
         [0105]    In addition the PIN  102  would be temporarily stored on the client and then used to generate a suitable differential key element  103  for the next session private key  20 . 
         [0106]    The example embodiment show the use of a PIN as a “thing the user must know” in order to achieve two factor authentication. An alternative embodiment could use any form of personally identifiable information including but not limited to thumb prints or other biometrics. 
         [0107]    The example embodiment uses subtraction to produce a differential key element by subtracting a PIN from a private key of a client side key pair. An alternative embodiment could use any calculation that allows the personally identifiable factor to be combined with a second file element in order to produce a useable private key in a client side key pair. 
         [0108]    The above describes only some embodiments of the present invention and modifications obvious to those skilled in the art can be made thereto without departing from the scope and spirit of the present invention. 
       INDUSTRIAL APPLICABILITY 
       [0109]    Embodiments of the invention may be applied in contexts where authentication of apparatus or an apparatus plus user combination is required to be verified prior to further communication with that apparatus.