Abstract:
A system and method for protecting data transmitted across a private network is disclosed. A secure channel is established so that the client computer can securely transmit a password to the server computer. Once the password has been transmitted, future transmissions use the password to encrypt data by the sending computer and decipher the data at the receiving computer. In one embodiment, passwords expire after a certain amount of time and are thereafter renegotiated. In another embodiment, the password is successively modified by a counter value further preventing unauthorized persons from discovering the password used to encrypt the data. By using passwords rather than public-key encryption methods, less system resources are required to maintain data confidentiality. An information handling system securely transmitting data within a private network as well as a computer program product programmed to perform the encryption processing are further disclosed.

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The present invention relates in general to a method and system for securing private networks. Still more particularly, the present invention relates to an improved method and system encrypting information between server and client computers in a private network. 
   2. Description of the Related Art 
   A computer network becomes disproportionately more difficult to manage as it increases in size, complexity and geographic dispersion. Management of the network involves configuration of software available on the machines or for a user in the network, coordination of access to shared resources and implementation of security measures. In addition, communication traffic on the computer network is monitored to ensure that the system is configured appropriately to reduce security risks and to improve efficiency. 
   Computer network security typically is implemented from the point of view that computer networks external to an enterprise are inherently untrusted and that computer networks internal to an enterprise are inherently trusted. As a result, security tends to be implemented using perimeter, or point of access, security mechanisms where communications from the external network enter into the internal network. One common way to implement connectivity with computers external to the enterprise is by encrypting and authenticating such communications using a protocol such as Secure Socket Layers (SSL). Such a system, however, does not protect against internal security breaches. 
   One way communications internal to an enterprise could be protected would be by encrypting internal communications using public key encryption such as used in SSL. Public key encryption uses a pair of asymmetric keys for encryption. One of these pairs is referred to as a “public” key and is shared with others, while the other key is a “private” key which is never distributed and is always kept secret. When data is encrypted using the public key, it can only be deciphered using the private key, and vise-versa (i.e., data encrypted using the private key can only be deciphered using the public key). In order to establish the secure link between two computers, one computer initiates a “handshake” with another computer to exchange public keys and establish a secure connection. 
   Using public key encryption on a private network presents challenges to the enterprise. First, while performing handshakes between every computer on the private network would secure the network, the security processing would result in poor performance on the network as more resources would be devoted to implementing security. A second challenge faced when confronting the first challenge, is determining which connections need to be secure in order to prevent unintentional disclosure of sensitive information. For example, an employee sending medical information to the company&#39;s medical department may want the information to be kept secret from others not in the medical department. However, the same employee sending a bulletin intended for all employees probably does not care to encrypt the information. 
   What is needed, therefore, is a way to seamlessly secure certain communications across a private network without overloading system resources and without making the system too complex to efficiently manage. 
   SUMMARY 
   It has been discovered that data can be secured between a client computer and a server computer by first establishing a secure link between the two computers using a public-key encryption methodology followed by the client computer transmitting a password that the client wishes to use to encrypt subsequent information flowing between the client and server computers. The server computer keeps track of clients and the clients&#39; corresponding passwords for use with future communications with such clients. 
   In one embodiment, a server designed to receive confidential information is programmed to respond to client requests with a message informing the client that the server accepts encrypted data. Following the receipt of the server&#39;s response, the client initiates the public-key handshaking and sends the server a password that the client would like to use for future transmissions. 
   In another embodiment, the password is modified periodically to prevent a third party from eventually discovering the password used by the client. One way the password can be modified is by including a counter with the password. In this manner, someone would not only need to know the original password set by the client, but would also need to know the number of transmissions previously sent between the client and the server. Another way the password can be modified is by periodically (i.e., every 24 hours) requiring the client to renegotiate a new password by establishing the secure public-key channel between the client and the server and transmitting a new password to the server. A combination of these two password modification schemes can also be implemented for further securing communications between the client and server computers. 
   The foregoing is a summary and thus contains, by necessity, simplifications, generalizations, and omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the present invention, as defined solely by the claims, will become apparent in the non-limiting detailed description set forth below. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be better understood, and its numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings. The use of the same reference symbols in different drawings indicates similar or identical items. 
       FIG. 1  is a high level system drawing showing components involved in the present invention; 
       FIG. 2  is a data diagram showing data across the private network between the client and server computers; 
       FIG. 3  is a flowchart showing client establishing a password with server; 
       FIG. 4  is a flowchart showing server processing an encrypted submission from client; 
       FIG. 5  is a flowchart showing the client renegotiating a password after the password expired; 
       FIG. 6  is a flowchart showing the password being modified to enhance security; and 
       FIG. 7  is a block diagram of an information handling system capable of performing the present invention. 
   

   DETAILED DESCRIPTION 
   The following is intended to provide a detailed description of an example of the invention and should not be taken to be limiting of the invention itself. Rather, any number of variations may fall within the scope of the invention which is defined in the claims following the description. 
     FIG. 1  shows a high level system diagram showing components involved in securing communications between client computer  100  and server computer  150  across private network  140 . As shown, client computer  100  includes client&#39;s public key (CPK)  110 . Client&#39;s public key  110  is sent to other computers as a key for encrypting data. When client&#39;s public key is sent to another computer, the other computer encrypts data using the public key and sends the encrypted data back to client. Client computer then deciphers the encrypted data using client&#39;s private key (CpK)  120 . The exchange of public keys is the basis of Diffie-Hellman type encryption used to establish Secure Socket Layers (SSL) security on the Internet and in other applications. 
   Client&#39;s public key  110  is sent through private network  140  to server computer  150 . Server computer receives client&#39;s public key  110  and transmits server&#39;s public key (SPK)  160  back to client. Neither client computer  100  nor server computer  150  discloses their respective private keys (client&#39;s private key  120  and server&#39;s private key  170 ). The public keys are exchanged to establish a secure channel across private network  140 . 
   As will be appreciated by those skilled in the art, private network  140  may be an local area network, such as an intranet. Gateway computer  190  can be used to connect private network  140  to Internet  195  in order to access computers located in distant locations. Also, as will be appreciated by those skilled in the art, while described as being used in a preferred embodiment of a private network, the present invention is useful in any network environment, including the Internet, to secure data transmitted between computers. 
   Once a secure connection is established by the exchange of client&#39;s public key  110  and server&#39;s public key  160 , client computer selects and transmits password  130  used in future communications with server computer  150 . Password  130  is received by server  150  and stored in database  180  along with the client&#39;s address. Thereafter, when client computer  100  sends a packet of data to server computer  150 , the server computer retrieves the client&#39;s password from database  180  and uses the password to decipher client&#39;s data packet. 
     FIG. 2  is a data diagram showing data flowing through private network  140  between client computer  100  and server computer  150 . Client computer  100  contacts server computer  150  and initiates handshake  200  by transmitting client&#39;s public key  205  across private network  140  and received at step  210  by server computer  150 . Server computer then completes the handshake (step  215 ) by transmitting server&#39;s public key  220  across private network to client computer  100 . Note that during the handshake processing, the data is transmitted across an unsecured channel within private network. However, after the handshaking is complete, a secure channel exists between client computer  110  and server computer  150 . 
   Client computer  100  then selects a password (step  225 ) and transmits password  230  across the secure channel created within private network  140  to server computer  150 . Server computer  150  is programmed to accept any password sent by client computer  100 . Alternatively, server computer can be programmed to require that password  230  conform to certain rules (i.e., certain length, contain at least some numeric data, etc.). Server computer  150  accepts client password and associates the password with the client computer&#39;s address (step  235 ). Server computer also stores the client computer address and the password for future referencing. 
   Client computer  100  prepares data that is to be processed by server computer  150  (step  240 ). The data is encrypted (step  245 ) using password  230 . Encrypted data file  250  is transmitted across private network  140  to server computer  150 . Note that a secure channel does not exist for the transmission of encrypted data file  250 . However, eavesdroppers or other snoopers are unable to view the contents of encrypted data file  250  since it was encrypted using password  230 . When encrypted data file  250  is received by server computer  150  (step  255 ), the data file is deciphered using the password that server computer  150  received and stored in step  235 . Once encrypted data file  250  is deciphered, server computer  150  processes the data (step  260 ). Server  150  prepares data to be returned to client computer (step  265 ). In order to make sure the responsive data is protected, server computer  150  encrypts the responsive data using the stored password (step  270 ). Encrypted response data  275  is transmitted across private network  140  and received by client computer  100  where it is deciphered using the password (step  280 ). The deciphered response date can then be processed by client computer  100  (step  285 ). 
   By establishing a password between client computer  100  and server computer  150 , data can be safely transmitted between the computers in an encrypted fashion without the overhead involved with establishing and maintaining secure connections between the machines. Problems with establishing and maintaining secure connections is exacerbated when multiple clients establish secure connections with multiple servers impacting system performance and throughput. 
     FIG. 3  shows a flowchart to establish a password and send encrypted data across a private network. Client computer begins its processing at step  300  and sends client&#39;s public key to the server computer (step  310 ). Server computer begins its processing at step  305  and receives client&#39;s public key (step  315 ). Server computer responds by sending server&#39;s public key back to client (step  320 ) where it is received by client computer (step  325 ). At this point, the pubic keys have been exchanged and a secure connection can be established. Client computer select a password to use in further communications with the server (step  330 ). The password is encrypted using server&#39;s public key (step  335 ). The encrypted password is then sent to the server computer (step  340 ). The server computer receives the encrypted password (step  345 ). The server then deciphers the password using server&#39;s private key (step  350 ). As a public key-private key pair, only the private key can be used to decipher data that was encrypted using the public key. The server computer now stores the client computer address and the password that was chosen by the client (step  355 ). 
   Back at the client computer, data is encrypted using the password that was sent to the server (step  325 ). After the data is encrypted, the encrypted data is sent to the server computer (step  360 ). Client computer is now able to continue sending and receiving encrypted data with server computer using the password that is now known by both computers. Server computer receives the encrypted data sent by the client computer (step  370 ) and deciphers the data using the stored password (step  375 ). This portion of the encryption processing is concluded, terminating at client (step  365 ) and server (step  380 ). 
     FIG. 4  shows how subsequent data can be sent from the client computer to the server computer without the need for establishing a secure channel. Client computer begins processing at step  400  thereafter determining whether the data to be sent to the server is sensitive or confidential (decision  402 ). If the data is sensitive or confidential, “yes” branch  403  is taken whereupon the data is encrypted (step  405 ) using the password established in  FIG. 3  before it is sent to the server (step  410 ). On the other hand, if the data is not sensitive or confidential, decision  402  branches to “no” branch  404  bypassing the encryption step and sending the plain data to the server in step  410 . One way the determination can be made as to whether the data is sensitive is by storing sensitive data in a particular location (i.e., subdirectory or database table) on the nonvolatile storage device attached to the client computer. Another way the determination can be made is by displaying a dialog box to the user prior to the transmission and having the user select whether the transmission contains sensitive or confidential information. 
   Server computer begins its processing at step  415  thereafter receiving the data file from the client computer (step  420 ). The server determines whether the data file is encrypted (decision  422 ). If the data is encrypted, “yes” branch  423  is taken whereupon steps  425  and  430  are performed as described below. If the data file is not encrypted, “no” branch  424  is taken bypassing the deciphering steps. One way the server can determine whether the received file is encrypted is by reserving a particular file type or other designation for the file being transmitted from the client computer. Another way the server can make the determination is by analyzing the internal contents or structure of the transmitted file and, based either upon a particular header or file organization, determining that the file is encrypted. 
   Along with the data file, the server computer received the network address of the client computer. The network address of the client computer was associated with the password supplied by the client computer. The server uses the network address of the client computer to look up the client&#39;s password (step  425 ). Once the password is located, the encrypted data is deciphered using the password. The data is processed and the server computer prepares a response based on the data (step  435 ). 
   The server determines whether the response contains sensitive or confidential information (decision  437 ). If the response is not sensitive or confidential, “no” branch  439  is taken bypassing the encryption step. On the other hand, if the response contains sensitive or confidential information, “yes” branch  438  is taken and the server computer encrypts the responsive data using the password (step  440 ). The response (encrypted or non-encrypted) is then sent back to the client computer (step  445 ) and this section of server processing is concluded at  450 . 
   The client computer receives the response data (step  455 ) and determines whether the response is encrypted (decision  457 ). If the response is encrypted, “yes” branch  458  is taken and the response is deciphered using the password (step  460 ). If the response is not encrypted, the deciphering step is bypassed by “no” branch  459 . Client processing is then terminates at step  465 . 
     FIG. 5  shows a flowchart used to renegotiate a stale password. Client computer begins processing at step  500  whereupon it encrypts data using the password previously shared between the client and server computers (step  505 ). Client computer then sends the encrypted data to the server computer (step  510 ). Server computer begins processing at step  515  thereafter receiving the encrypted data sent from client computer (step  520 ). Server computer uses the client computer&#39;s network address to look up the client&#39;s password. In this embodiment, a time/date stamp is included in the database storing the client passwords. The time/date stamp is compared with the current date to determine whether the password is still valid (step  530 ). 
   If the password is older than an allowed maximum time value (i.e., older than 24 hours), then the password is deemed to be stale and a new password is required by the system. If the password is not expired, “no” branch  535  is taken leading to the predefined process to decipher and process the encrypted data (step  570 ). On the other hand, if the password is expired, “yes” branch  540  is taken whereupon the server computer notifies the client computer that the password is expired and a new password is needed (step  545 ). The notification may take the form of an electronic message sent to the client computer. The client computer receives the password expired notice (step  550 ) whereupon it performs the steps necessary to establish a secure connection with the server computer and select a new password and re-encrypts the data using the new password (predefined process  555 , see also  FIG. 3 ). Once the password and re-encrypted data are sent, this portion of client processing is completed and terminated at step  560 . 
   Once a new password has been selected and a secure connection has been established between the client and server computers, the new password is received by the server computer along with the re-encrypted data (step  565 ) where it is stored in the database replacing the expired password. The encrypted data is then deciphered and processed (step  570 ) before this section of server processing is terminated at step  575 . 
     FIG. 6  shows a flowchart used to repetitively modify the password used to encrypt data files in order to provide more security than a static password. Client processing commences at step  600  whereupon the client computer initializes a password by establishing a secure connection and sending the password to the server computer (step  610 )(see  FIG. 3  for further details). Server processing commences as step  605  whereupon it receives and stores the password selected by the client computer (step  615 )(see  FIG. 3  for further details). The client initializes a counter that is combined with the password (step  620 ). The client computer then modifies the password using the counter (step  630 ). Meanwhile, the server computer also initializes a counter (step  625 ), modifies the password the same way that the client computer modified the password (step  635 ) and stores the password and counter in a database (step  640 ). Client then encrypts data using the modified password and send the encrypted file to the server (step  650 ). The server receives the encrypted file, looks up the password (including the counter) deciphers the data file using the password and counter, and processes the data (step  670 ). Both the client and the server then increment the counter (steps  655  and  675 , respectively) and modifies the password using the new counter value (steps  660  and  680  respectively). Both the client and server computer continue to send and receive encrypted data using continually modified passwords (loops  665  and  685 , respectively). By continually modifying the password, an eavesdropper or snoop would not only have to know the original password, but would also have to know the number of data packets that have been sent between the client and server computers in order to successfully decipher the data. 
     FIG. 7  illustrates information handling system  701  which is a simplified example of a computer system capable of performing the copy processing described herein. Computer system  701  includes processor  700  which is coupled to host bus  705 . A level two (L2) cache memory  710  is also coupled to the host bus  705 . Host-to-PCI bridge  715  is coupled to main memory  720 , includes cache memory and main memory control functions, and provides bus control to handle transfers among PCI bus  725 , processor  700 , L2 cache  710 , main memory  720 , and host bus  705 . PCI bus  725  provides an interface for a variety of devices including, for example, LAN card  730 . PCI-to-ISA bridge  735  provides bus control to handle transfers between PCI bus  725  and ISA bus  740 , universal serial bus (USB) functionality  745 , IDE device functionality  750 , power management functionality  755 , and can include other functional elements not shown, such as a real-time clock (RTC), DMA control, interrupt support, and system management bus support. Peripheral devices and input/output (I/O) devices can be attached to various interfaces  760  (e.g., parallel interface  762 , serial interface  764 , infrared (IR) interface  766 , keyboard interface  768 , mouse interface  770 , and fixed disk (FDD)  772 ) coupled to ISA bus  740 . Alternatively, many I/O devices can be accommodated by a super I/O controller (not shown) attached to ISA bus  740 . 
   BIOS  780  is coupled to ISA bus  740 , and incorporates the necessary processor executable code for a variety of low-level system functions and system boot functions. BIOS  780  can be stored in any computer readable medium, including magnetic storage media, optical storage media, flash memory, random access memory, read only memory, and communications media conveying signals encoding the instructions (e.g., signals from a network). In order to attach computer system  701  another computer system to copy files over a network, LAN card  730  is coupled to PCI-to-ISA bridge  735 . Similarly, to connect computer system  701  to an ISP to connect to the Internet using a telephone line connection, modem  775  is connected to serial port  764  and PCI-to-ISA Bridge  735 . 
   While the computer system described in  FIG. 7  is capable of executing the copying processes described herein, this computer system is simply one example of a computer system. Those skilled in the art will appreciate that many other computer system designs are capable of performing the copying process described herein. 
   One of the preferred implementations of the invention is a client application, namely, a set of instructions (program code) in a code module which may, for example, be resident in the random access memory of the computer. Until required by the computer, the set of instructions may be stored in another computer memory, for example, in a hard disk drive, or in a removable memory such as an optical disk (for eventual use in a CD ROM) or floppy disk (for eventual use in a floppy disk drive), or downloaded via the Internet or other computer network. Thus, the present invention may be implemented as a computer program product for use in a computer. In addition, although the various methods described are conveniently implemented in a general purpose computer selectively activated or reconfigured by software, one of ordinary skill in the art would also recognize that such methods may be carried out in hardware, in firmware, or in more specialized apparatus constructed to perform the required method steps 
   While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this invention and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this invention. Furthermore, it is to be understood that the invention is solely defined by the appended claims. It will be understood by those with skill in the art that is a specific number of an introduced claim element is intended, such intent will be explicitly recited in the claim, and in the absence of such recitation no such limitation is present. For non-limiting example, as an aid to understanding, the following appended claims contain usage of the introductory phrases “at least one” and “one or more” to introduce claim elements. However, the use of such phrases should not be construed to imply that the introduction of a claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an”; the same holds true for the use in the claims of definite articles.