Abstract:
A method for authenticating an entity at a first data resource, the method comprising the steps of: sending a first request token from the entity ( 100 ) to a token distribution unit ( 20 ) to request a first one-way authentication token, the first request token being a function of authentication information provided by the entity ( 100 ); sending the first one-way authentication token from the token distribution unit ( 20 ) to the entity ( 100 ); sending the first one-way authentication token from the entity ( 100 ) to the first data resource ( 200 ) to authenticate the entity ( 100 ) at the first data resource ( 200 ); sending the first one-way authentication token from the first data resource ( 200 ) to the token distribution unit ( 20 ) to validate the first one-way token; and invalidating the first one-way token.

Description:
PRIORITY DATA 
       [0001]    This application is a continuation of, and claims benefit of priority to, U.S. application Ser. No. 11/253,958, titled “Authentication Method and Devices”, filed Oct. 19, 2005, whose inventors were Eckehard Hermann and Dieter Hermann Kessler, which claims benefit of priority to European Patent Application Serial No. EP 04 025 186.0, titled “Authentication Method and Devices”, filed Oct. 22, 2004, whose inventors were Eckehard Hermann and Dieter Hermann Kessler, both of which are incorporated by reference in their entirety as though fully and completely set forth herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a method for authenticating an entity at a data resource. 
       THE PRIOR ART 
       [0003]    Access to data resources such as data bases or applications running on a main-frame computer is typically controlled by providing an authorized user with a password. However, since data resources are nowadays more and more distributed, the authentication information, such as the user name and the password or a certificate, must be sent over sometimes unsecured channels between the client application of the user and the addressed data resource. This is particularly a problem if a user intends to access a data resource which is not directly connected the client application but only via one or more intermediate servers or the like so that the authentication information is passed on over various channels. In such a situation, the user cannot control, whether all of the sections of the communication between the client application and the addressed data resource are indeed secured. 
         [0004]    One way of improving the security of authentication information is the use of tokens, i.e., virtual objects, passed from the client to the data resource for authentication. To obtain a token, a client sends at first authentication information to a trusted third party. If the client is authenticated, the trusted third party issues a token to the client, wherein in some systems the trusted third party also verifies the authorization of the client to access a certain data resource. By means of this token the client can access the various data resources, which may validate the token with the trusted third party. As a result it is no longer the authentication information itself, which is sent over the possibly unsecured channels, but only a token. 
         [0005]    However, even if tokens are used, an attacker could listen to the communication between the client and one or more data resources and try to gain access by replaying bit sequences sent to the data resources, which may contain the token. Accordingly, there is still a considerable risk that the identity of a user is “hijacked” and subsequently used to gain access to various data sources of a distributed network without being authorized. 
         [0006]    It is therefore the problem of the present invention to provide a method for authenticating an entity, such as a user or a client application, at a data resource, which overcomes the above explained disadvantages of the prior art and allows a secure access control, even if the communication between the entity and the data resources uses one or more unsecured channels. 
       SUMMARY OF THE INVENTION 
       [0007]    According to a first aspect of the present invention, this problem is solved by a method for authenticating an entity at a first data resource, the method comprising the steps of:
       sending a first request token from the entity to a token distribution unit to request a first one-way authentication token, the first request token being a function of authentication information provided by the entity,   sending the first one-way authentication token from the token distribution unit to the entity;   sending the first one-way authentication token from the entity to the first data resource to authenticate the entity at the first data resource,   sending the first one-way authentication token from the first data resource to the token distribution unit to validate the first one-way token; and   invalidating the first one-way token.       
 
         [0013]    Accordingly, instead of the single token of the prior art, there are two types of tokens: Request tokens, which are sent from the entity to the token distribution unit and one-way authentication tokens, which are received by the entity in response and which can be used for authentication of the entity at the data resource only once. After the one-way authentication token is sent from the data resource to the token distribution unit to verify that it is a correct authentication token, it is invalidated. 
         [0014]    As a consequence, each authentication token travels from the token distribution unit to the entity, from the entity to the data resource and back to the token distribution unit. The described life-cycle is only passed once and only in the indicated direction, before the one-way authentication token is invalidated. As a consequence, a data resource receiving the same one-way authentication token for the second time, will immediately recognize that a replay attack or the like is taking place and block the access to its data. This allows to transmit the authentication token over an unsecured channel without the risk of a hijack of the identity of the origin of the authentication information. 
         [0015]    A further advantage of the present invention is that the one-way authentication token can be made much smaller than ordinary digitally signed tokens. The authentication token may for example consist of only 16 bytes, which facilitates its integration into existing programs. 
         [0016]    Preferably, the token distribution unit sends the first request token used in the first method step to the entity in response to the authentication information being sent to the token distribution unit from the entity. Accordingly, a client sends at first authentication information, such as a username and a password or a certificate, to the token distribution unit and receives in response a request token, which allows to obtain an authentication token for a single access of a data resource. 
         [0017]    The security of the communication is further increased, if the one-way authentication token is valid only for a predefined limited time. By contrast, the first request token can preferably be reused by the entity to obtain further one-way authentication tokens to authenticate the entity at the first data resource again and/or at other data resources. Since the request token is in contrast to the authentication token preferably not transmitted over the unsecured channel(s) between the entity and the data resource(s), there is no risk that this token is intercepted by an attacker. 
         [0018]    In a particularly preferred embodiment of the first aspect of the invention the method comprises
       sending a second request token from the token distribution unit to the first data resource in response to the validation of the first one-way authentication token; and preferably   sending the second request token from the first data resource to the token distribution unit to request a second one-way authentication token;   sending the second one-way authentication token from the token distribution unit to the first data resource;   sending the second one-way authentication token from the first data source to a second data resource to authenticate the entity also at the second data resource;   sending the second one-way authentication token from the second data resource to the token distribution unit to validate the second one-way authentication token; and   invalidating the second one-way authentication token.       
 
         [0025]    Accordingly, the inventive concept of using one-way authentication tokens can also be extended to a situation, wherein a first data resource has to contact a second data resource to meet a request from the entity. To this end, the process is repeated, i.e. the first data resource is provided with a second request token to obtain a second authentication token, which it will then forward for authentication at a second data resource. The second data resource in turn validates the second authentication token at the token distribution unit, which leads finally to the invalidation of the second authentication. It is apparent that the described method can be cascaded so that chains of data resources of any length can be securely accessed by the method of the present invention, even if one or more of the channels linking the chained data resources are unsecured. 
         [0026]    According to a further aspect, the present invention is directed to a token distribution unit comprising a request token issue unit issuing a first request token in response to the receiving of authentication information from an entity, an authentication token issue unit issuing a one-way authentication token in response to the receiving of the first request token from the entity, a validation unit validating the one-way authentication token for a data resource, and an invalidation unit invalidating the authentication token issued by the authentication token issue unit and received with a validation request form the data resource. 
         [0027]    Finally, the present invention relates according to a still further aspect to a first data resource comprising an access control unit receiving a one-way authentication token to gain access to the data of the first data resource, a validation request unit sending a received one-way authentication token to a token distribution unit and obtaining a request token in response, and an authentication token obtaining unit sending the request token to the token distribution unit to obtain a one-way authentication token for a single access of the first data resource at a second data resource. 
         [0028]    Further dependent claims relate to preferred embodiments of the method and the token distribution unit. 
     
    
     
       SHORT DESCRIPTION OF THE DRAWINGS 
         [0029]    In the following detailed description presently preferred embodiments of the invention are described with reference to the drawings which show: 
           [0030]      FIG. 1 : An arrangement of a web server connected to several data resources to illustrate the problem underlying the present invention; and 
           [0031]      FIG. 2 : a schematic representation of the various steps performed in a method in accordance with a preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0032]      FIG. 1  illustrates a typical situation as it is encountered in today&#39;s distributed networks of data resources: A web server  100  provides access for a user not only to the files of the web server  100  itself but also to several data resources either directly or indirectly connected to the web server  100 . The data resources may in an exemplary configuration comprise one ore more applications  200 ,  500 , running for example on one or more mainframe computers (not shown), and a server  300  with a data base managing program handling requests for a database  400 , such as an Adabas database. 
         [0033]    When a user at the web server  100  wants to access data at the database  400 , his request is initially sent from the web server  100  to the application  200 , which processes the request and sends a corresponding request to the server  300 , which finally sends a request to the database  400 . Whenever one of the data resources  200 ,  300  or  400  receives a request, it requires authentication information which enables the respective data resource to verify, whether the requesting user is authorized to access the requested data. As a result, the authentication information has in the above example to be communicated over the channels a, b and c (cf.  FIG. 1 ). 
         [0034]    Whereas in the past the various applications, server and databases were typically localized in one, generally secure location interconnected by secure channels, the various data resources are nowadays typically distributed over several locations and interconnected by more or less open networks such as the Internet or an Intranet. As a consequence, the channels a, b, c, d are no longer secured channels. In particular, a user entering his authentication information at the web server  100  does not know and cannot control, whether one or more of the channels a, b, c, which are used to process his request, are secured or not. Therefore, there is a considerable risk that the authentication information supplied by a user and thereby his identity may be hijacked on its way to the data server  400 . 
         [0035]    The method according to the invention improves the security for the authentication process by providing an Integrated Authentication Framework (IAF)  20  as shown in  FIG. 2 . In the following, the function of the IAF  20 , in particular its distribution of various tokens, is described with respect to the specific network of data resources shown in  FIG. 2 . However, it is to be understood, that the IAF  20  and the method steps described below can also be applied to any other network of distributed data resources. Further, whereas the description refers in the following to a data request of a user at a web server  100 , the method and the system of the present invention can also be used for data being sent from the web server  100  to any of the data resources  200 ,  300 ,  400  and  500  or data being simply processed at one of the data resources. 
         [0036]    A user trying to access data at any of the data resources  200 ,  300 ,  400  or  500  enters the authentication information at the web server  100 . The web server  100  forwards the authentication information of the user, typically the username and the password or a certificate, to the IAF  20 . The channel f is a secured channel similar to all other channels g, h, and i, which preferably directly connect the IAF  20  to the various data resources  200 ,  300 ,  400 ,  500 . Instead of a (human) user, the whole process may also be started by an application running on the web server  100  or an interconnected client application, which requests data from one of the data resources  200 ,  300 ,  400  or  500  of the network. In this case the authentication information sent to the IAF will be provided by the client application (not shown), for example in the form of a certificate. 
         [0037]    
       15 
     
         [0038]    When the IAF  20  receives the authentication information from the web server  100 , it verifies its content and issues in response a first request token to the web server  100 . The request token is a unique set of bytes, typically 16 bytes, created by the IAF  20 , which enables the web server  100  to obtain from the IAF  20  one or more one-way authentication tokens, which the web server  100  can then use to access data at one of the data resources  200  or  500 . Whenever the web server  100  needs a further one-way authentication token, it will again send the request token to the IAF  20 , which will again respond with issuing a further one-way authentication token to the web server  100 . The first authentication token for the web server  100  can alternatively be sent already together with the initial issuing of the request token to reduce data traffic from and to the IAF  20 . 
         [0039]    The exchange of the authentication information and the request token between the web server  100  and the IAF is illustrated by the two continuous arrows on the left side of  FIG. 2 . The path of the one-way authentication tokens used in the method illustrated by  FIG. 2  is indicated by dotted or dash-dotted arrows. As can be seen, the first authentication token called “authentication token  1 ” is sent from the IAF  20  to the requesting web server  100 . If the web server  100  needs data from the data resource  200 , it will forward the authentication token  1  to the data resource  200 . 
         [0040]    In order to verify that the received one-way authentication token  1  has indeed been issued by the IAF  20 , the data resource  200  will sent the one-way authentication token  1  received over the unsecured channel a back to the IAF  20  via the preferably secured channel g. The IAF  20 , which preferably keeps track of all issued one-way authentication tokens, validates the correctness of the authentication token received from the data resource  200 . The IAF  20  may further check, whether a predefined time limit for the validity of the authentication token  1  has already expired and, if so, instruct the data resource  200  not to allow the access to the requested data. Otherwise, i.e. if the validation is successful, the IAF  20  issues a corresponding message to the data resource  200 , which then responds to the request of the web server  100 . 
         [0041]    Finally, the IAF invalidates the authentication token  1 , which can then no longer be used to access any data in the network of  FIG. 2 . As can be seen, the authentication token  1  has a life-cycle, which starts with the issuing at the IAF  20  and which terminates with its final invalidation at the IAF  20 . For any further request of data or sending of data from the web server  100  to the data resource  200  or another connected data resource  500 , the web server  100  will need a further one-way authentication token. In this case, the web server  100  will send once more its request token to the IAF  20 , which will respond with a further one-way authentication token. 
         [0042]    Since any one-way authentication token of the described method will only be used once and therefore only once travel along the possibly unsecured channel a (or one of the other channels b, c, d, see below), it is of no concern if an attacker listens on one of the unsecured channels for authentication information. Even if he succeeds to somehow catch the one-way authentication token during its single path from the web server  100  to the data resource  200 , he can not reuse the authentication token for any unauthorized data access. This is, since the IAF  20  will not validate a second use of the already invalidated authentication token, when it is received again from the data resource  200  for validation. Alternatively such a reused authentication token may already be rejected by the data resource  200 , if it keeps track of the received one-way authentication tokens. 
         [0043]    If the data requested by the web server  100  is not available on the data resource  200 , it might be necessary that the data resource  200  contacts a further data resource, for example the server  300 . This can be done as follows: 
         [0044]    When the data resource  200  validates the authentication token  1  by sending it along the channel g to the IAF  20 , it receives as a response not only a confirmation about the validity of the authentication token  1  but also a request token. This second request token—the first request token is the request token of the web server  100 —can be used by the data resource  200  to obtain an a one-way authentication token, called in the following authentication token  2 , for accessing the server  300 . To this end, the data resource  200  sends its request token to the IAF  20 , which verifies the request token and responds with the requested one-way authentication token  2 . Alternatively, the IAF  20  can provide the data resource  200  with the first one-way authentication token together with sending the request token, if it is desired to reduce the data traffic on the channel g. 
         [0045]    In a similar manner as the web server  100  uses the one-way authentication token  1  to access the data resource  200 , the data resource  200  can now access the server  300 , which will then validate the one-way authentication token  2  by sending it back to the IAF  20 , where it is checked and finally invalidated. 
         [0046]    As can be seen from  FIG. 2 , this process can be repeated to access the data base  400 , so that finally the one-way authentication tokens  1 ,  2  and  3  are used for the overall transaction. However, since all of the three tokens are used only once, the overall request from the web server  100  to the data base  400  can be processed via one or more unsecured channels without the risk of a hijacking of authentication information and thereby the identity of a user. 
         [0047]    When the described method is used with all data sources  200 ,  300 ,  400  and  500  participating, there will finally be a situation, wherein each data resource is provided with its respective request token. Each request token is bound to one member of the network, i.e. the web server  100  or any of the data resources  200 ,  300 ,  400  and  500 . However, the request tokens may also be provided with a time limit so that they will be automatically invalidated when a predefined time has elapsed. Clearly, the time limit may be different for different participants of the network. 
         [0048]    Finally, the request tokens may further be used by any of the participants of the network to get more information about the user. For example, if the data resource  500  needs additional information about the user in order to respond to a request from the web server  100  or to execute a certain task, it can send a command such as “getinfo(request token)” to the IAF  20 . Since any request token used by the various data resources and the web server  100  is a function of the authentication information initially sent to the IAF  20  and stored by the IAF, the IAF can then provide the required information, for example the full name of a user, his address, his degree of authorization etc.