Abstract:
A method and system for tracking communications in a client-server environment. The method includes the steps of sending a first request from the client to the server over a first connection, sending a first key from the server to the client over the first connection, sending the first key from the client and a second request to the server over a second connection, and sending a response to the second request and a second key distinct from the first key from the server to the client over the second connection. The system includes a client for establishing a terminal connection with a server and a server in communication with the client. The server further includes key generator means generating a plurality of keys for transmission to the client, authentication means in communication with the key generator means receiving the keys from the client to recognize the keys at the server, and discarding means linked to the key generator means for disposing of previously transmitted keys.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of application Ser. No. 09/009,832, filed Jan. 20, 1998. 
    
    
     MICROFICHE APPENDIX 
     A Microfiche Appendix is included in this application and comprises 2 sheets, having a total of 175 frames. The Microfiche Appendix contains material which is subject to copyright protection under the laws of the United States and other nations. The copyright owner has no objection to the facsimile reproduction by any person of the Microfiche Appendix, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever. 
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to a computer client-server environment. In particular, the invention relates to a method and system for providing secure transactions and for tracking the state of communications in a public network. 
     In an ever-increasing fashion, networks are used to transfer data among computers throughout the world. These networks utilize a protocol in which data groups, called packets, are requested by one computer and sent by another computer. With the prevalent use of the global public network known as the Internet, computers located remotely from each other can share information by requesting and delivering these packets. In a client-server environment, the client and a server are software or hardware applications which are used to communicate in a request/response manner. The separate client and server applications can be resident on a single computer or separated by thousands of miles in separate computers connected via a network. 
     The world-wide web, or “Web,” is one such information system implemented on the Internet. The Web is based on hypertext technology, which allows certain elements of a document or “page” to be expanded or linked to other elements elsewhere on the “Web” of interconnected computers. The Web may be viewed by users via “browsers,” which essentially are local computer programs that read hypertext documents and display graphics. The Web is gated or navigable via these hypertext documents and is structured using links between these documents. The address of individual documents are known as “universal resource locators,” or “URLs.” 
     In the Web&#39;s data exchange implementation, the local computer requesting information may be considered a “client” and the computer responding to the requests may be considered a “server.” Data exchange between the client and server is performed via discontinuous, unrelated and standalone request/response pairs for information. In order to more efficiently handle requests from many clients, the server initiates a new connection for every request. This connection is subsequently broken after each response is transmitted. The server is thereafter available to service a new connection requested from another client. 
     For every request from the same client, a new connection must be established, although this typically is done fairly quickly. Consequently, a user (or client) who has made previous requests is treated no differently from one who has not. The server responds to each request for information in the order received. Thus, if the client is accessing the server in a series of interdependent cumulative steps, the client not only must request a new connection, but must resend the results of the previous requests to the server. The existence of a new connection and a new set of requests that is sent from the client to the server is often concealed from the user. Thus, the client transparently remembers the “state” of the exchanges between the client and the server, and returns this information to the server so that the exchange can continue appropriately. Often, this “state” information is sent with the URL in each new request. 
     With this configuration, the state information is stored primarily at the client. If the client does not reestablish a connection with a particular server immediately, some of the state information may become irrelevant or stale as the server updates its own database information. Thus, the state information stored at the client may become irrelevant or useless after a period of time, and the client will need to reestablish the current state with a particular server again. 
     As the number of cumulative requests to an “interesting” server increases, however, the required amount of information that the client must send to the server also increases. An “interesting” Web application running on a server must acquire and retain state information from the client. With the bandwidth limitations of conventional phone lines or network cable, the retransmitted information increases the amount of time it takes for a client to send a request to the server and to receive a response. More importantly, valuable or confidential information, such as credit card account numbers, is repeatedly sent and is subject to increased risk of interception by undesired parties. Furthermore, should the integrity of the communications link between the client and the server be interrupted at any time, much of the state information retained at the client or the server may be lost, thereby requiring the client to proceed through a previous series of requests to establish the state where communications broke off. 
     The following practical example illustrates these shortcomings in the prior art. In this example, a server runs a “site,” or “Web application” program, which processes mail order requests for clothing. A consumer uses his computer, the client, to purchase a pair of pants over the Internet by executing a series of requests to a server: 
     
       
         
               
               
             
           
               
                 EXAMPLE I 
               
               
                   
               
             
             
               
                   Request No. 1: 
                 Client requests “pants.” 
               
               
                   
                 Client sends no state information. 
               
               
                   
                          In response, the server gets list of pants and 
               
               
                   
                       sends the data back to the client. 
               
               
                 Request No. 2: 
                 Client requests “brown” and sends 
               
               
                   
                 state information “clothing=pants.” 
               
               
                   
                       In response, the server gets a list of 
               
               
                   
                       brown pants and sends the data 
               
               
                   
                       back to the client. 
               
               
                 Request No. 3: 
                 Client requests “show me size 32” and sends 
               
               
                   
                 state information “color=brown”; “clothing=pants.” 
               
               
                   
                       In response, the server retrieves a list of 
               
               
                   
                       brown size 32 pants and sends the data 
               
               
                   
                       back to the client. 
               
               
                 Request No. 4: 
                 Client requests “show me cuffed” and sends 
               
               
                   
                 state information “color=brown”; “size=32”; 
               
               
                   
                 “clothing=pants.” 
               
               
                   
                       Server retrieves from its database the one 
               
               
                   
                       cuffed brown size 32 pair of pants and sends 
               
               
                   
                       the data back to the client. 
               
               
                 Request No. 5: 
                 Client requests “buy these, my CC#  is 
               
               
                   
                 1234-4321-1121-3231” and sends state information 
               
               
                   
                 “clothing=pants”; “color=brown”, “size=32”, 
               
               
                   
                 pantlegs=cuffed.” 
               
               
                   
                       Server retrieves from its database the 
               
               
                   
                       brown size 32 cuffed pants, processes the 
               
               
                   
                       purchase using client&#39;s credit card number, 
               
               
                   
                       and sends an appropriate response to the 
               
               
                   
                       client. 
               
               
                   
               
             
          
         
       
     
     The relationship between the client and the server is “stateless,” in that their communication consists of transmissions bounded by disconnects and reconnects for each new request or response pair. The amount of data sent from the client to the server typically increases with every request by the client in order to ensure that each request from the client is recognized by the server in relation to previous requests. As those skilled in the art will appreciate, the state information sent in the final request necessarily repeats all of the state information accumulated from all previous communications within the same context. It is thus conceivable that a lengthy transaction could require the transmission of hundreds of pieces of state information between the client and server. 
     It is an objective of the present invention to provide a method for minimizing the amount of information to be transmitted between the client and the server during these network transactions. 
     It is also an objective of the present invention to increase the security and reliability of the client-server communications. 
     It is a further objective of the present invention to centralize and secure client-specific data and retain it at the server. 
     SUMMARY OF THE INVENTION 
     To meet the above objectives, the present invention replaces the information that tracks the results of the previous requests over established and reestablished communications links using an identifier string called a “key.” Instead of an ever-increasing set of information transmitted from the client to the server and back, the embodiment described herein localizes the state between the client and server at the server and associates the state with the key string. The substantive information from the previous commands, requests or responses need not be retransmitted upon the establishment of each new connection with a server. Rather, the server keeps track of this information and the server and client both reference this information with only the key. 
     One aspect of the present invention therefore provides a method for tracking communications in a stateless client-server environment comprising the steps of sending a first request from the client to the server over a first communication link or connection, sending a first identifier from the server to the client over the first link, sending the first identifier from the client and a second request to the server over a second link, and sending a response to the second request and a second identifier distinct from the first identifier from the server to the client over the second link. The first and second identifiers are thus distinct and can identify the state of the particular client to the server by representing the present state of communications, or simply identify the client based on the last secure identifier string exchange made between the server and the client. This identification information and state information may preferably be stored at the server, thereby providing the most secure and efficient repository for state or identification-tracking data. 
     In another aspect of the present invention, the server performs the steps of exchanging identifiers upon receipt of a new request from a distinct client. In particular, a method is provided comprising the steps of receiving a first request from a client over a first link, sending a first identifier to the client over the first link, receiving the first identifier from the client and a second request over a second link, and sending a response to the second request and a second identifier distinct from the first identifier to the client over the second link. 
     In yet another aspect of the present invention, a method for tracking communications in a client-server environment is provided including the steps of establishing a first connection between a client and a server, authenticating the client at the server, generating a first key in the server corresponding to the communication session and sending the first key to the client. After disconnecting the first connection, a second connection is established between the client and server, with the client generating a request and sending the request and the first key to the server. The server verifies the first key and generates a response (optionally using any local state information previously stored at the server and associated with the first key) to the request and a second key at the server. The response and the second key are then sent back to the client. In this fashion, the server is able to keep track of the state or status of a series of communications with a particular client by internally referencing the state of such communications with keys. A new key is sent to the client along with each response to a client&#39;s request. Any subsequent communication by the client is then transmitted back to the server along with a particular key that is recognized by the server. 
     In another aspect of the present invention, the keys used by the server to track the state of communications sessions are interchanged or changed often, preferably by the server, before any response is sent back to the client. 
     In still another aspect of the present invention, a system for tracking communications in a client-server environment is provided that includes a client computer operative to establish a connection with a server computer, and a server computer in communication with the client. The server includes a key generator means generating a plurality of keys for transmission to the client, a verification means in communication with the key generator means, the verification means receiving the keys from the client to recognize the client, and a discarding means linked to the key generator means for disposing of previously transmitted keys. 
     In yet another aspect of the present invention, a method for tracking communications in a client-server environment is provided including the steps of establishing a first connection between a client and a server, generating a first key in the server corresponding to a session between the client and the server, sending the first key to the client, disconnecting the first connection between the client and the server, establishing a second connection between the client and the server, generating a request at the client and sending the request and the first key to the server through the second connection, recognizing the first key at the server, generating a second key at the server, the second key being unrelated to the first key, processing the request of the client at the server to generate a response, sending the response and the second key back to the client over the second connection, and disconnecting the second connection between the client and the server. 
     In another aspect of the present invention, the keys used to track the communications are sequential and have no information or relationship to the data being transmitted between the client and the user. 
     In yet another aspect of the present invention, the keys used to track the communications are randomly generated or have no sequential relationship to one another. 
     In still another aspect of the present invention, the keys are invalidated by the server once they are used in a request or request/response pair so that they will never be used again or at least until the occurrence of a certain event (e.g., revised after 1 year, revised after 1000 sessions, etc.). 
     In another aspect of the present invention, the keys are invalidated after a specified period of time has elapsed. 
     In yet another aspect of the present invention, a method for tracking communications in a client-server environment is provided including the steps of establishing a connection between a client and a server, receiving a first key from the server, generating a request at the client, sending the request and the first key to the server through the connection, and receiving a response to the request and a new key from the server over the connection. 
     The present invention thus allows for the emulation of a stateful network environment. The recognition between the client and server requires only the transmission of the new request and a key string. Thus, from the user&#39;s or client&#39;s perspective, the communication with the server appears to be stateful and permanent, since there is no retransmission of old data. 
     The present invention alleviates problems found in the prior art by eliminating the need for any summary retransmission of state data. While the prior art requires this information to adequately describe the new instruction to the server, the present embodiment records this information at the server, which associates the current state information of the client with an unrelated or related key value. This results in a streamlined, secure environment for network conversations. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     The invention, together with further objects and attendant advantages, will best be understood by reference to the following detailed description, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram showing various client-server connections in a network system utilized in the preferred embodiment of the present invention. 
     FIG. 2 is a state diagram showing a prior art client-server exchange. 
     FIG. 3 is a flow diagram showing the exchange between the client and the server of FIG. 1 during an authentication operation as used in the method of the present invention. 
     FIG. 4 is a flow diagram showing the steady-state operation for requests between the client and the server over the network shown in FIG. 1 for the method of the preferred embodiment of the present invention. 
     FIG. 5 is a block diagram showing a system of the present invention utilized in the method shown in FIGS. 3 and 4. 
     FIG. 6 is a state diagram similar to that of FIG. 2 showing exchanges between the client and the server during an operating example of the present invention of FIGS. 3-5. 
     FIG. 7 is a flow diagram of the steps undertaken by the software implementation of the preferred embodiment of the method of FIGS.  3  and  4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A. Description of the Stateless Client-Server Environment and the Prior Art Environment 
     Referring now to the drawing figures, FIG. 1 is a diagram illustrating the Internet environment in which the preferred embodiment of the secure session tracking method operates. It should be noted that one skilled in the art would contemplate an implementation of the present invention in other non-Internet-based applications, and thus the present invention should not be restricted to implementation on the Internet. It shall be noted that “client” and “server” in the figures described herein need not be separate machines. A client can be any software that makes a request of a server, which is another module of running software. 
     Each client  50  preferably comprises a workstation which is capable of executing various computer programs and reading and/or writing to and from memory contained within the workstation. The workstations that may comprise all or part of the client may be fixed or portable personal computers adapted to operate in communication with the server  52  or the network  30 . In the preferred embodiment, the client  50  may simply comprise a single personal computer or microprocessor suitable for executing computer programs and processing data information input to the computer. Suitable hardware for the client  50  as shown in FIG. 1 is a SPARCstation 5 manufactured by Sun Microsystems® Inc., having at least 64 megabytes of memory and a 1 gigabyte hard disk drive. Personal computers such as the Dell® Dimension XPS P133s, manufactured by Dell Corporation®, having the same system parameters may be implemented as the workstation for client  50 . The server and workstations are platforms which can preferably utilize processors capable of executing the software in the attached Microfiche Appendix, or Microsoft® Windows 95®, manufactured by Microsoft Corporation®. One skilled in the art would recognize that numerous configurations of hardware and software may be utilized to implement the preferred embodiment disclosed herein. 
     In the prior art systems on which the preferred embodiment would be implemented, the user of the network requests information via the Internet from the client  50 . The server  52  receives the request and delivers the requested information back to the client  50 . In this stateless Internet environment, the client  50  first establishes a logical or physical connection or link  54  with the server  52 . It should be noted that the existence and/or permanency of any other connections or links between client  50  and server  52  (e.g. physical network cabling) does not affect the stateless nature of the logical connection or link  54 . After establishing a connection (or link), the client  50  sends the request to the server  52  through the connection  54 . After processing the request, the server  52  sends a response back to the client  50 . The connection  54  is then broken or moved to an “inoperative” state by the server, the client, or both. This allows the server  52  to participate in the establishment of a new connection, receive a request, and transmit a response to another client. 
     If the user wishes to make another follow-up request, either based on or independent from the previous request, the client  50  must reestablish or establish a new connection  54  with the server  52 . Preferably, the client  50  remembers or stores in memory through conventional means the URL, link or location of the particular server  52  or group of servers with which the client  50  was connected in the previous communication. To establish a connection, therefore, the user preferably enters the next follow-up request, and the client  50  automatically attempts a second connection with the server  52 . When a second connection  54  is established, server  52  is in an initial state and does not typically recognize the client  50  from the first connection as being the same client. 
     In fact, in prior art systems, the server is typically in this initial state regardless of how many connections have been or will be established. This is the “stateless” nature of the client-server environment. As a result, the client  50  must communicate to the server  52  information resulting from or pertaining to previous communications in order to establish the previous “state” of communications, if client  50  wishes his new request to be processed relative to such communications. In the prior art, this is done by resending all the previous state information to the server  52  with the new request. 
     FIG. 2 illustrates a state diagram of this prior art implementation, which is similar to the implementation of Example 1 previously described. As shown in FIG. 2, as time progresses from the top of the figure towards the bottom, the client sends requests to the server, and the server sends subsequent responses back to the client. Because each request and response pair is separated by a break in the connection between the server and the client, the client is forced to send data along with subsequent requests to the server so that the server will understand the state of the previous communications. For example, after the client has received a first response (response  1 ) from the server, the communication between the client and server is broken. At a subsequent time, the client sends a follow up request (request  2 ) to the server, but must send state information (data  1 ) that communicates to the server information relating to the previous communication between the client and the server relating to request  1 . The server receives the request and processes a response based on the data (data  1 ) received along with the second request (request  2 ). A response (response  2 ) is then sent from the server back to the client and the communication link is broken again. In a subsequent time, the client decides to send another request (request  3 ) to the server. Again, the client must send state information relating to the previous requests (request  1  and request  2 ). This additional information (data  1  and data  2 ) must be sent along with the third request (request  3 ) to the server. The server receives the third request and processes the request in light of the state information (data  1  and data  2 ) and returns a response (response  3 ) back to the client. The communication link is then broken again. Finally, when a fourth request (request  4 ) is sent to the server, state information from the previous requests (data  1 , data  2 , and data  3 ) must also be sent to the server to properly establish and inform the server of the state of previous communications. As the example of FIG. 2 demonstrates, as time moves forward, the amount of information sent with the new requests increases. Furthermore, data elements relating to previous communications must be continuously resent. 
     B. Description of the Method and System of the Preferred Embodiment 
     In the preferred embodiment of the method described, the client  50  instead sends an identifier or “key,” which the server  52  uses to identify any previously stored information for various clients. The interaction between client  50  and server  52  in the preferred embodiment is described in FIGS. 3 and 4. The creation and validation of keys at the server  52  are described in FIG.  4 . 
     The secure session tracking method of the preferred embodiment preferably operates with an initial authentication stage to identify or recognize the user or client. This authentication procedure is shown in the flow diagram of FIG.  3 . 
     Turning now to FIG. 3 in combination with previously discussed FIG. 1, the operations on the left side of the diagram take place at the client  50 , or on the client-side  56 . Similarly, operations on the right side of the diagram take place at the server  52 , or on the server-side  58 . Beginning at start boxes  60  and  62 , the client  50  and server  52  are operating independently from each other. At step  64 , the client  52  seeks and establishes a connection with the server  54 . The server  54  then verifies the connection and sends a confirmation to the client  50  (step  66 ). The client or server essentially recognize in this step that some form of communication or acknowledgment thereof is established. Client  50  receives the confirmation (step  68 ), and sends authentication information, such as a password, to server  52 . The server  52  receives this information and verifies the authentication information (step  72 ). This may be carried out using known techniques, such as by checking the password against a database of known passwords, or by recognizing the format or configuration of a password. In accordance with the present invention, if the authentication information is approved, the server  52  preferably generates a first key  74  (step  72 ), which is preferably a random character string from preferably base-62 character set. Preferably, the key encapsulates no data contained in the communications between the client and server. In the alternative, however, the key may actually contain state information embedded or encrypted into the character string. It should be noted that the most diverse (largest) character set from which individual characters for individual spaces in the multiple-character key are chosen is preferable. The base-62 character set includes the characters [a . . . z]+[A . . . Z]+[ 0  . . .  9 ] and being at least 1 character long. This preferred character set would avoid any characters that cause problems with the software (client or server) or in transmission to allow for the most secure implementation. One skilled in the art would recognize that the length of a key utilized in the present invention can vary widely. 
     In response to the authentication information transmitted by client  50  in step  70 , the server  52  preferably transmits an authentication verification and the first key  74  (step  72 ). The client  50  then receives the authentication verification and the first key (step  76 ). Finally, the connection between client  50  and server  52  is broken. This allows server  52  to handle requests from other clients. Boxes  80  and  82  mark the completion of the initial authentication routine. This process may be repeated if the client  50  sends an invalid key to server  52  as described below. 
     It is important to note that a login name and/or password is not necessarily used to recognize the client. Thus, the step  70 , the verification of authorization information in step  72 , or the transmission of login verification in step  76  from the server  52  to the client  50  may be eliminated while remaining within the scope of the invention. As an example, a scenario without login information can occur by establishing a connection between the client  50  and the server  52 , generating a first key  74  in response to a request lacking a key or authentication information from the client  50 , and transmitting it from the server  52  to the client  50 . 
     FIG. 4 illustrates the steady-state operation of the method of the preferred embodiment herein. Here, either a first key  74  or some other previously sent key has been transmitted from the server  52  to the client  50 , which preferably stores the key value in memory or nonvolatile storage. As in FIG. 3, the operations on the left portion of the diagram occur at the client  50  and the operations on the right portion of the diagram occur at the server  52 . 
     First, the client  50  and the server  52  must establish a communications connection or link. Step  82  (client-side) and step  84  (server-side) represent steps  64  through  68  in FIG.  3 . After the connection is established, the server  52  is in some initial state  86 . The client  50  preferably sends a request  90  and a previously sent key  92  (step  88 ) and the server  52  receives them (step  94 ). Next, the server  52  validates key  92  (step  96 ). Note that upon the initial communication between the client  50  and the server  52 , the client will not have a key to send back to the server. Thus, the present diagram represents communications after at least an initial key is received by the client from the server. 
     This is preferably done by comparing the value of key  92  with key values stored in a key storage database at the server  52 . However, other methods of key validation are possible. For example, the key  92  may be self-validating in that the server  52  may be able to immediately recognizing the key&#39;s information or format. The server  52  may also ensure that the key has not been timed out. For example, the server may know when the particular key was sent in a response and by comparing that time with the time of the current request, the age of the key can be determined, and the age value of the key can be compared with a predetermined time value that has been found to be an acceptable age. It is a more secure optional enhancement to disallow keys that have been assigned and unused by the client for an overly long period of time. These two processes will be described in more detail in conjunction with FIG. 5 below. 
     After the key  92  is validated, the server  52  uses any state information recorded in its database to process the request. The server  52  uses the key  92  to emulate a certain environment for the client  50  by keeping track of state information. As a result, it can appear to the client  50  that the server  52  has been continually connected to it since the client  50  does not have to resend every piece of state information with each new request to the server  52 . 
     If the key  92  received in the server  52  is invalid, the server will not perform the request from the client. Optionally, the server may enter an error processing routine, eventually returning an error message to the client. Such routines are well-known in the art. 
     Preferably, after the initial authentication by the client  50 , the state of the communications session is tracked by the server  52  and retained upon termination of the connection through transmission of a response back to the client  50 . The initial state established by the server is shown as “server0” (reference numeral  86 ). After the server  52  performs the request  90  (step  100 ) using any stored state information identified by key N ( 92 ), it updates any state information it has determined may be necessary for possible future requests in a database. Next, the server creates a new key  106  (step  104 ). Preferably, the key is non-sequential or unrelated to the former key  92 . This method is one way to increase security by ensuring that no key value can be used twice. 
     Finally, the server  52  sends a response  108  to the client&#39;s request and the new key  106  to the client  50  (step  110 ). The server  52  then returns to its initial state  86  (step  112 ), and the client  50  and server  52  logically or physically break the connection between them (steps  114  and  116 ). For any subsequent connection, the routine in FIG. 3 repeats starting at steps  82  and  84 . 
     The keys are preferably sent between the server  52  and the client  50  via coding blocks hidden from the user. To protect the confidentiality of the information referenced by the key and to prevent unauthorized viewing of the key, the key may be encoded, encrypted or partially encrypted by a number of known conventional means. In the alternative, if encryption is not a concern, the keys may be sent as part of the URL area on the client&#39;s browser program. Furthermore, the entire response or request may be encrypted for decoding by the key or some other means. 
     When the preferred embodiment of the invention is applied to the client-server stateless environment which is HTTP communication (Hyper Text Transfer Protocol, the protocol used on the Internet for World Wide Web traffic), the key values are preferably stored as “cookies.” This term is a known term in the context of HTTP and specifically is a means for servers to instruct clients where to store sets of information specified by the server, to be unchanged by the client, so that the client can transparently return the information to the server with subsequent requests. Other ways exist for a server to “pass” information to a client and for the client to return it with subsequent requests. In the above-stated HTTP-based environment, for example, such information may be sent in the content of an HTML document, or in the content of a link, or URL. All of these options for the storage or communication of key values are well-known to one skilled in the art. 
     If desired, the encryption of the key and the entire communication between client and server provides the additional advantage of discouraging any unauthorized users from attempting to decode confidential private information. Decryption of the key only would provide an unauthorized user with a meaningless character string which preferably has no direct relationship to the transmitted sensitive information apart from the sensitive data actually stored on the server. Furthermore, as will be described below, the keys preferably have a finite “lifetime,” so any actual decryption of a key that might occur would not be useful indefinitely in attempting to retrieve data in an unauthorized fashion from the server  52 . 
     FIG. 5 shows a server system  115  used to implement the preferred embodiment of the invention and illustrates the operation of the server  52 . The functionality of the server  52  preferably is founded on the database  118  shown in the server system  115 . Constant updating to the database  118  allows the system to act intelligently and thereby creates the emulation of a stateful environment across any request/response pairs for a given client. 
     There are preferably five processes performed by various system means implemented by the software of the server  52 : key validation (process  122 ), request interpretation (process  124 ), response generation (process  126 ), and key generation (process  128 ). The discussion of the operation of the server  52  will be divided into two categories: (1) optimal authentication to the server and (2) steady-state operation. 
     The initial authentication verification (process  120 ) described in steps  70 - 76  of FIG. 3 preferably interacts with the database  118  by comparing authentication information with known values in the database  118 . At this authentication juncture, it is preferably assumed that there is no valid key for the client  50  and one must be provided by the server  52  for the client  50  to continue. If the information provided is the same as that in the database  118 , then the client  50  is authorized to continue. At this point, the server  52  preferably generates a random identifier value to store in the database (step  128 ). As described previously, this value, referred to hereinafter as a “key,” is a string of letters and/or numbers of a desired length. After the key has been generated, the server  52  preferably sends login verification and the first key  74  to the client  50 . 
     After a connection is established between the client  50  and server  52 , a steady-state operation begins, and the server  52  waits for two items of information from the client: (1) a request  90  for data and (2) a previously sent key  92 . The server  52  first evaluates any new connections from clients and checks any incoming keys that are received (process  122 ). If the server  52  does not find a key  92 , the server generates a response (process  126 ) that directs the client  50  to login to the system using process  120 . State at this point would be “server0” for that connection. If no login sequence is utilized, the server  52  directs the client  50  to some other starting state through which a first key  74  can be generated or assigned to recognize the user or client  50 . 
     If the server  52  receives a key  92  of the proper format, the key validation (process  122 ) continues by interfacing with the database  118 . Preferably, the value of the key  92  is first compared with a plurality of key values stored in the database  118 . If none of the values match, the key and client are not “recognized” and the server  52  operates as it did when no key was sent. If the value is recognized, then the process preferably continues to determine if the key has been “timed-out.” Preferably, key values stored in the database  118  are associated with a date and time value after which the key is no longer valid. These time values are preferably based on the time and/or date of creation of each key. The server ignores keys in the database created before a certain date or time. In the preferred embodiment, particular keys are preferably valid for less than one hour. This is an additional security measure which ensures that the key transmitted is being sent by the authorized user and that the state associated with the key remains “fresh.” 
     Without this device, an unauthorized user could, for example, make a connection with the server  52  several days later, send a new request  90  with the previously sent key  92 , and continue where the authorized user left off. If the time when the key  92  is received by the database  118  is earlier than the “time-out” time period, then the key  92  is deemed valid. Again, if no valid or non-timed-out key is found, the client  50  must log in to the server  52  again. 
     Before the response is sent back to the client  50 , the server  52  generates a new key (process  128 ) by generating a new random key string of set length. This is the new key  106 . The key generation procedure preferably stores the value of the key  106  in the database  118  along with the present state of communications with this particular client, thus replacing the old key  92 . Implicitly, the old key  92  is invalidated since it is no longer stored in the database  118 . Other methods can be utilized by the server to ensure that the value of the old key  92  is not reused. This may entail storing the value in the database and comparing the new key  106  with a list of used keys, discarding the used keys, or retrieving keys to be used from a finite, stored set of keys and discarding them after use. 
     The server  52  completes its connection with the client  50  by sending back to the client  50  the new key  106  and the response  108  and terminates the connection. At this stage, the server  52  is free to make a connection with another client and repeat the same processes. When the client  50  establishes another connection with the server  52 , the client  50  will not have to resend the state information describing what has already taken place since this data is stored in the server&#39;s database  118  in association with new key  106 . Rather, the transmission of key  106  to the server will forego the need for a relogin or a retransmission of state information. 
     The key validation process ( 122 ) and key generation process ( 128 ) allow the server  52  to behave in an intelligent and efficient manner. The preferred embodiment herein solves many communication inefficiencies that would otherwise occur. For example, various problems may be incurred if a client sent the same request twice in prior art systems. Prior art servers would not be storing any state information, and the client would send all the state information and the server would have no “memory” of what happened previously. Since each transaction is completely independent, the results of the request would be duplicated. In some cases, multiple sets of goods could be mistakenly ordered, database data could conflict, or sensitive information could be disseminated. Furthermore, because information about state is stored on a server, critical state information may be stored in a physically stable environment. This becomes important should client hardware fail, or should the client switch hardware. 
     Using the secure tracking method described, each request appears to the user of the client not to be independent. While the client-server environment is still stateless, the server  52  “remembers” what the client has previously done by storing information identified by the key  92 . Thus, the present embodiment can solve these multiple request dilemmas by maintaining the database  118 . Here, for example, the server  52  could clear the stored information in the database after a product is purchased, or trigger a warning or other subroutine should a request be made more than once. 
     FIG. 6 shows a state diagram illustrating communications between the client  50  and the server  52 , and the advantages of the presently preferred embodiment as compared with the prior art may be more easily seen. In particular, comparison should be made with the state diagram of FIG.  2 . FIG. 6 shows four request and response pairs for particular requests made by the client of the server. The four request and response pairs are preferably separated by breaks in the communication link between the client and the server after a particular response is received by the client. As shown in this example, an initial request (request  1 ) is sent by the client to the server. The server processes request  1  and generates a key (key  1 ) that represents the state of communications. The present state of communications between this particular client and the server is stored in the data storage area (data  1 ) in association with key  1 . The server then sends the response (response  1 ) to the request along with key  1  back to the client. Communications are then broken. Preferably, after a short period of time passes, the client sends a second request (request  2 ) to the server along with the key (key  1 ) which was sent by the server to the client during the previous communication. The server processes request  2  and generates a response (response  2 ) based on the state of previous communications (data  1 ) which has been retrieved from the data storage area using the key  1  which was sent to the server with request  2 . Using data  1 , the server produces a response  2  and a generates a new key. The new key (key  2 ) now represents the present state of communications, which has been stored as data  1  and data  2  in the data storage area. The key  2  and response  2  are then sent back to the client. 
     Next, the client sends a third request (request  3 ) and the previously sent second key (key  2 ) to the server. The server processes request  3  given the data relating to the previous communications which has been retrieved using key  2 . Again, the server generates a third key which it associates with stored data relating to the previous communications (data  1 , data  2  and data  3 ). The response (response  3 ) and the new key (key  3 ) is then sent back to the client, and the operation continues. 
     Note that as time moves forward, the amount of information sent with new requests to the server remains substantially constant, and that all that is sent is a key which represents data at the server containing the state of previous communications or information from those previous communications. Thus, preferably most or all of the information which is required for subsequent processing by the server is kept at the server, and the need for retransmission of information is preferably eliminated. 
     Preferably, the system and method of the preferred embodiment is implemented partially on software running on the server  52 . The software preferably implements the Java Virtual Machine®, a proprietary software module of Sun Microsystems, Inc.; and operates using the general steps as will be described below. 
     FIG. 7 shows a high-level flow diagram of the various steps undertaken by the software in implementing the method of the preferred embodiment. As shown in box  200 , the server  52  first receives an entire request from the client  50 , while leaving the new HTTP connection open. As shown in box  202 , the server then separates the URL from the request and hands off processing to a submodule in the software that performs the key authentication steps. As shown in box  204 , if the submodule requires specific authorization or access to data previously related to the present session with the present client, the key which was sent with the request is separated from the request and verified (box  205 ). As described above, verification preferably consists of, but is not limited to, checking for the particular key in a database of known previously issued keys and checking to ensure that the key was issued within a predetermined amount of time. Next, the server continues to process the request (box  206 ), forming a response and using any and all data sources available to it, including calls to other databases ( 207 ). Some of the data sources may require the transmitted key in order to retrieve data. The server then generates a new key value ( 208 ). 
     As shown in box  210 , the server  52  then bundles the new key value with other relevant information into a response appropriately formatted for transmission back to the client  50 . The server sends the response back to the client along the open HTTP connection (box  212 ). As shown in box  214 , once successful delivery is reasonably assured, the server  52  and the client  50  drop their mutual connection and the server  52  updates the local data base of the valid keys, replacing the old key with the new key value. 
     The objects for this software implementation are included in the Microfiche Appendix attached hereto, and the Java summary documents containing related object hierarchy are also included. One skilled in the art can readily utilize known methods, software and systems to implement the embodiment as described herein and exampled in the source code provided in the attached Microfiche Appendix. 
     Of course, it should be understood that a wide range of changes and modifications can be made to the preferred embodiments described above. For example, the method and system described herein should not be limited to the Internet. Indeed, the system and method may be implemented on any type of network, including private intranets or semi-permanent cellular or wired networks. Furthermore, one skilled in the art would recognize that a wide variety of software and hardware platforms may be utilized to implement the present invention. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting and that it be understood that it is the following claims, including all equivalents, which are intended to define the scope of this invention.