Abstract:
Methods and systems consistent with the present invention provide dynamic security policies that change the granularity of the security at the node level, process level, or socket level. Specifically, a channel number and virtual address are associated with various processes included in a process table. Since a security policy is required for all processes, secure and insecure processes located on the same channel may communicate with one another. Moreover, processes located on different channels may communicate with one another by a gateway that connects both channels. This scalable blanketing security approach provides an institutionalized method for securing any process, node or socket by providing a unique mechanism for policy enforcement at runtime or by changing the security policies.

Description:
RELATED APPLICATIONS 
     The following identified U.S. patent applications are relied upon and are incorporated by reference in this application. 
     U.S. patent application Ser. No. 09/458,043, now U.S. Pat. No. 6,970,941, entitled “SYSTEM AND METHOD FOR SEPARATING ADDRESSES FROM THE DELIVERY SCHEME IN A VIRTUAL PRIVATE NETWORK,” filed Dec. 10, 1999. 
     U.S. patent application Ser. No. 09/457,917, entitled “TRULY ANONYMOUS COMMUNICATIONS USING SUPERNETS WITH THE PROVISION OF TOPOLOGY HIDING,” filed Dec. 10, 1999, now U.S. Pat. No. 6,798,782. 
     U.S. patent application Ser. No. 09/457,889, now U.S. Pat. No. 6,977,929, entitled “METHOD AND SYSTEM FOR FACILITATING RELOCATION OF DEVICES ON A NETWORK,” filed Dec. 10, 1999. 
     U.S. patent application Ser. No. 09/457,916, entitled “SANDBOXING APPLICATIONS IN A PRIVATE NETWORK USING A PUBLIC-NETWORK INFRASTRUCTURE,” filed Dec. 10, 1999. 
     U.S. patent application Ser. No. 09/457,894, entitled “SECURE ADDRESS RESOLUTION FOR A PRIVATE NETWORK USING A PUBLIC NETWORK INFRASTRUCTURE,” filed Dec. 10, 1999, now abandoned. 
     U.S. patent application Ser. No. 09/458,020, entitled “DECOUPLING ACCESS CONTROL FROM KEY MANAGEMENT IN A NETWORK,” filed Dec. 10, 1999. 
     U.S. patent application Ser. No. 09/457,895, now U.S. Pat. No. 6,938,169, entitled “CHANNEL-SPECIFIC FILE SYSTEM VIEWS IN A PRIVATE NETWORK USING A PUBLIC NETWORK INFRASTRUCTURE,” filed Dec. 10, 1999. 
     U.S. patent application Ser. No. 09/458,040, entitled “PRIVATE NETWORK USING A PUBLIC-NETWORK INFRASTRUCTURE,” filed Dec. 10, 1999. 
     U.S. patent application Ser. No. 09/457,915, now U.S. Pat. No. 6,870,842 entitled “USING MULTICASTING TO PROVIDE ETHERNET-LIKE COMMUNICATION BEHAVIOR TO SELECTED PEERS ON A NETWORK,” filed Dec. 10, 1999. 
     U.S. patent application Ser. No. 09/457,896, entitled “ANYCASTING IN A PRIVATE NETWORK USING A PUBLIC NETWORK INFRASTRUCTURE,” filed Dec. 10, 1999, now abandoned. 
     U.S. patent application Ser. No. 09/458,021, entitled “SCALABLE SECURITY ASSOCIATIONS FOR GROUPS FOR USE IN A PRIVATE NETWORK USING A PUBLIC-NETWORK INFRASTRUCTURE,” filed Dec. 10, 1999. 
     U.S. patent application Ser. No. 09/458,044, entitled “ENABLING SIMULTANEOUS PROVISION OF INFRASTRUCTURE SERVICES,” filed Dec. 10, 1999, now abandoned. 
     FIELD OF THE INVENTION 
     The present invention relates generally to data processing systems and, more particularly, to a private network using a public-network infrastructure. 
     BACKGROUND OF THE INVENTION 
     As part of their day-to-day business, many organizations require an enterprise network, a private network with lease lines, dedicated channels, and network connectivity devices, such as routers, switches, and bridges. These components, collectively known as the network&#39;s “infrastructure,” are very expensive and require a staff of information technology personnel to maintain them. This maintenance requirement is burdensome on many organizations whose main business is not related to the data processing industry (e.g., a clothing manufacturer) because they are not well suited to handle such data processing needs. 
     Another drawback to enterprise networks is that they are geographically restrictive. The term “geographically restrictive” refers to the requirement that if a user is not physically located such that they can plug their device directly into the enterprise network, the user cannot typically utilize it. To alleviate the problem of geographic restrictiveness, virtual private networks have been developed. 
     In a virtual private network (VPN), a remote device or network connected to the Internet may connect to the enterprise network through a firewall. This allows the remote device to access resources on the enterprise network even though it may not be located near any component of the enterprise network. For example,  FIG. 1  depicts a VPN  100 , where enterprise network  102  is connected to the Internet  104  via firewall  106 . By using VPN  100 , a remote device D 1    108  may communicate with enterprise network  102  via Internet  104  and firewall  106 . Thus, D 1    108  may be plugged into an Internet portal virtually anywhere within the world and make use of the resources on enterprise network  102 . 
     To perform this functionality, D 1    108  utilizes a technique known as tunneling to ensure that the communication between itself and enterprise network  102  is secure in that it cannot be viewed by an interloper. “Tunneling” refers to encapsulating one packet inside another when packets are transferred between two end points (e.g., D 1    108  and VPN software  109  running on firewall  106 ). The packets may be encrypted at their origin and decrypted at their destination. For example,  FIG. 2A  depicts a packet  200  with a source Internet protocol (IP) address  202 , a destination IP address  204 , and data  206 . It should be appreciated that packet  200  contains other information not depicted, such as the source and destination port. As shown in  FIG. 2B , the tunneling technique forms a new packet  208  out of packet  200  by encrypting it and adding both a new source IP address  210  and a new destination IP address  212 . In this manner, the contents of the original packet (i.e.,  202 ,  204 , and  206 ) are not visible to any entity other than the destination. Referring back to  FIG. 1 , by using tunneling, remote device D 1    108  may communicate and utilize the resources of the enterprise network  102  in a secure manner. 
     Although VPNs alleviate the problem of geographic restrictiveness, they impose significant processing overhead when two remote devices communicate. For example, if remote device D 1    108  wants to communicate with remote device D 2    110 , D 1  sends a packet using tunneling to VPN software  109 , where the packet is decrypted and then transferred to the enterprise network  102 . Then, the enterprise network  102  sends the packet to VPN software  109 , where it is encrypted again and transferred to D 2 . Given this processing overhead, it is burdensome for two remote devices to communicate in a VPN environment. 
     VPNs provide security at the network layer of the OSI model and generally cover all applications. The OSI model is a well-known model used to describe the seven protocol layers in a standard TCP/IP protocol stack. The OSI model contains seven layers that use various forms of control information to communicate with their peer layers in other computer systems. This “blanket security” approach requires the VPN to secure all applications regardless of the individual needs of the application. Because of this drawback VPNs cannot differentiate between security at the application level or security at the node level. Moreover, when communicating between security domains controlled by different VPNs, multiple devices are required to allow the connection, such as firewalls and routers. These devices provide gateway services that enable data to be exchanged between various security domains. 
     Therefore, it is desirable to provide a dynamic security protocol that easily integrates into existing VPNs. 
     SUMMARY OF THE INVENTION 
     Methods and systems consistent with the present invention overcome the shortcomings of existing security protocols by providing dynamic security policies that may change the granularity of the security at the node level, process level, or socket level. Specifically, these shortcomings are met by having a security context that includes a channel number and virtual address associated with each process included in a process table. Since a security policy is required for all processes, secure and insecure processes located on the same channel may communicate with one another. Moreover, processes located on different channels may communicate with one another by a gateway that connects both channels. This scalable blanketing security approach provides an institutionalized method for securing any process, node or socket by providing a unique mechanism for policy enforcement at runtime or by changing the security policies. 
     In accordance with the purpose of the invention as embodied and broadly described herein, a method provides communication access between a first process and a second process. To provide access, the method appends security context information for the first process in a process table, and opens a socket between the first process and the second process. The method then transmits a packet from the first process to the second process through the open socket. Each packet contains security context information for the first process in the process table. 
     In another implementation, a method for providing secure communications between a first process and a second process is provided. The method obtains a channel number and a virtual address, and includes the channel number and the virtual address in a field corresponding to the first process in a process table. The method then transmits a datagram that contains the channel number and virtual address from the first process to a socket. The datagram is then received at the second process that contains the channel number and a second virtual address. 
     In another implementation, a method places processes executed in a node in a security context. The method sends a request from the node to a server to verify a username and a channel identification. In response to the request, the method receives security context information at the node from the server and initiates the process. The security context information includes a virtual address for the node. The method then appends the security context information and the channel identification for the process in a process table that is associated with the process. 
     This private network also provides flexible and dynamic mobility support. Sometimes, the device on which a node runs is relocated to a new physical location (e.g., a new office). In this situation, a problem arises because the nodes that send communications to the moving node will be unable to do so once the moving node relocates. This problem occurs because when the device moves, nodes that run on that device receive a new IP address. Some conventional systems solve this problem by using a proxy as a middleman between the source node and the destination node. In these systems, the source node sends a packet to the proxy, and the proxy then sends it to the destination node. Then, when the destination node moves, it updates the proxy with its new address so that it can continue to receive communications. Such systems incur significant processing overhead because of use of the proxy. The private network according to an implementation of the present invention does not use a proxy; instead, the private network sends communications directly from the sending node to the destination node. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This invention is pointed out with particularity in the appended claims. The above and further advantages of this invention may be better understood by referring to the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  depicts a conventional virtual private network (VPN) system; 
         FIG. 2A  depicts a conventional network packet; 
         FIG. 2B  depicts the packet of  FIG. 2A  after it has been encrypted in accordance with a conventional tunneling technique; 
         FIG. 3  depicts a data processing system suitable for use with methods and systems consistent with the present invention; 
         FIG. 4  depicts the nodes depicted in  FIG. 3  communicating over multiple channels; 
         FIG. 5  depicts two devices depicted in  FIG. 3  in greater detail; 
         FIGS. 6A and 6B  depict a flow chart of the steps performed when a node joins a VPN in a manner consistent with the present invention; 
         FIG. 7  depicts a process table used by the VPN in a manner consistent with the present invention; 
         FIG. 8  depicts a flow chart of the steps performed when sending a packet from a node of the VPN in a manner consistent with the present invention; 
         FIG. 9  depicts a flow chart of the steps performed when receiving a packet by a node of the VPN in a manner consistent with the present invention; and 
         FIG. 10  depicts a flow chart of the steps performed when logging out of a VPN in a manner consistent with the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Methods and systems consistent with the present invention provide a “Supernet,” which is a private network that uses components from a public-network infrastructure. A Supernet allows an organization to utilize a public-network infrastructure for its enterprise network so that the organization no longer has to maintain a private network infrastructure; instead, the organization may have the infrastructure maintained for them by one or more service providers or other organizations that specialize in such connectivity matters. As such, the burden of maintaining an enterprise network is greatly reduced. Moreover, a Supernet is not geographically restrictive, so a user may plug their device into the Internet from virtually any portal in the world and still be able to use the resources of their private network in a secure and robust manner. 
     Overview 
       FIG. 3  depicts a data processing system  300  suitable for use with methods and systems consistent with the present invention. Data processing system  300  comprises a number of devices, such as computers  302 - 312 , connected to a public network, such as the Internet  314 . A Supernet&#39;s infrastructure uses components from the Internet because devices  302 ,  304 , and  312  contain nodes that together form a Supernet and that communicate by using the infrastructure of the Internet. These nodes  316 ,  318 ,  320 , and  322  are communicative entities (e.g., processes) running within a particular device and are able to communicate among themselves as well as access the resources of the Supernet in a secure manner. When communicating among themselves, the nodes  316 ,  318 ,  320 , and  322  serve as end points for the communications, and no other processes or devices that are not part of the Supernet are able to communicate with the Supernet&#39;s nodes or utilize the Supernet&#39;s resources. The Supernet also includes an administrative node  306  to administer to the needs of the Supernet. 
     It should be noted that since the nodes of the Supernet rely on the Internet for connectivity, if the device on which a node is running relocates to another geographic location, the device can be plugged into an Internet portal and the node running on that device can quickly resume the use of the resources of the Supernet. It should also be noted that since a Supernet is layered on top of an existing network, it operates independently of the transport layer. Thus, the nodes of a Supernet may communicate over different transports, such as IP, IPX, X.25, or ATM, as well as different physical layers, such as RF communication, cellular communication, satellite links, or land-based links. 
     As shown in  FIG. 4 , a Supernet includes a number of channels that its nodes  316 - 322  can communicate over. A “channel” refers to a collection of virtual links through the public-network infrastructure that connect the nodes on the channel such that only these nodes can communicate over it. A node on a channel may send a message to another node on that channel, known as a unicast message, or it can send a message to all other nodes on that channel, known as a multicast message. For example, channel  1   402  connects node A  316  and node C  320 , and channel  2   404  connects node B  318 , node C  320 , and node D  322 . Each Supernet has any number of preconfigured channels over which the nodes on that channel can communicate. In an alternative embodiment, the channels are dynamically defined. 
     In addition to communication, the channels may be used to share resources. For example, channel  1   402  may be configured to share a file system as part of node C  320  such that node A  316  can utilize the file system of node C in a secure manner. In this case, node C  320  serves as a file system manager by receiving file system requests (e.g., open, close, read, write, etc.) and by satisfying the requests by manipulating a portion of the secondary storage on its local machine. To maintain security, node C  320  stores the data in an encrypted form so that it is unreadable by others. Such security is important because the secondary storage may not be under the control of the owners of the Supernet, but may instead be leased from a service provider. Additionally, channel  2   404  may be configured to share the computing resources of node D  322  such that nodes B  318  and C  320  send code to node D for execution. By using channels in this manner, resources on a public network can be shared in a secure manner. 
     A Supernet may also contain “linked” channels. These channels are linked by a gateway between the channels. The gateway allows the different channels to communicate with one another. With the gateway, a node on a channel may send a message to another node on a different channel. For example, gateway  410  connects channel  3   406  and channel  4   408 . Since channels  3  and  4  are linked, node A  316  and node B  318  may communicate with each other using channel  3   406  and channel  4   408 . 
     A Supernet provides a number of features to ensure secure and robust communication among its nodes. First, the system provides authentication and admission control so that nodes become members of the Supernet under strict control to prevent unauthorized access. Second, the Supernet provides communication security services so that the sender of a message is authenticated and communication between end points occurs in a secure manner by using encryption. By providing the security services, the Supernet enables scalable security from the socket level to the node level. Third, the system provides key management to reduce the possibility of an intruder obtaining an encryption key and penetrating a secure communication session. The system does so by providing one key per channel and by changing the key for a channel whenever a node joins or leaves the channel. Alternatively, the system may use a different security policy. 
     Fourth, the system provides address translation in a transparent manner. Since the Supernet is a private network constructed from the infrastructure of another network, the Supernet has its own internal addressing scheme, separate from the addressing scheme of the underlying public network. Thus, when a packet from a Supernet node is sent to another Supernet node, it travels through the public network. To do so, the Supernet performs address translation from the internal addressing scheme to the public addressing scheme and vice versa. To reduce the complexity of Supernet nodes, system-level components of the Supernet perform this translation on behalf of the individual nodes so that it is transparent to the nodes. Another benefit of the Supernet&#39;s addressing is that it uses an IP-based internal addressing scheme so that preexisting programs require little modification to run within a Supernet. 
     Lastly, the Supernet provides operating system-level enforcement of node compartmentalization in that an operating system-level component treats a Supernet node running on a device differently than it treats other processes on that device. This component (i.e., a security layer in a protocol stack) recognizes that a Supernet node is part of a Supernet, and therefore, it enforces that all communications to and from this node travel through the security infrastructure of the Supernet such that this node can communicate with other members of the Supernet and that non-members of the Supernet cannot access this node. Additionally, this operating system-level enforcement of node compartmentalization allows more than one Supernet node to run on the same machine, regardless of whether the nodes are from the same Supernet, and allows nodes of other networks to run on the same machine as a Supernet node. 
     Implementation Details 
       FIG. 5  depicts administrative machine  306  and device  302  in greater detail, although the other devices  304  and  308 - 312  may contain similar components. Device  302  and administrative machine  306  communicate via Internet  314 . Each device contains similar components, including a memory  502 ,  504 ; secondary storage  506 ,  508 ; a central processing unit (CPU)  510 ,  512 ; an input device  514 ,  516  and a video display  518 ,  520 . One skilled in the art will appreciate that these devices may contain additional or different components. 
     Memory  504  of administrative machine  306  includes the SASD process  540 , VARPD  548 , and KMS  550  all running in user mode. That is, CPU  512  is capable of running in at least two modes: user mode and kernel mode. When CPU  512  executes programs running in user mode, it prevents them from directly manipulating the hardware components, such as video display  518 . On the other hand, when CPU  512  executes programs running in kernel mode, it allows them to manipulate the hardware components. Memory  504  also contains a VARPDB and a TCP/IP protocol stack  552  that are executed by CPU  512  running in kernel mode. TCP/IP protocol stack  552  contains a TCP/UDP layer  554  and an IP layer  556 , both of which are standard layers well known to those of ordinary skill in the art. Secondary storage  508  contains a configuration file  558  that stores various configuration-related information (described below) for use by SASD  540 . 
     SASD  540  represents a Supernet: there is one instance of an SASD per Supernet, and it both authenticates nodes and authorizes nodes to join the Supernet. VARPD  548  has an associated component, VARPDB, into which it stores mappings of the internal Supernet addresses, known as a node IDs, to the network addresses recognized by the public-network infrastructure, known as the real addresses. The “node ID” may include the following: a Supernet ID (e.g., 0×123), reflecting a unique identifier of the Supernet, and a virtual address, comprising an IP address (e.g., 10.0.0.1). The “real address” is an IP address (e.g., 10.0.0.2) that is globally unique and meaningful to the public-network infrastructure. In a Supernet, one VARPD runs on each machine, and it may play two roles. First, a VARPD may act as a server by storing all address mappings for a particular Supernet into its associated VARPDB. Second, regardless of its role as a server or not, each VARPD assists in address translation for the nodes on its machine. In this role, the VARPD stores into its associated VARPDB the address mappings for its nodes, and if it needs a mapping that it does not have, it will contact the VARPD that acts as the server for the given Supernet to obtain it. 
     KMS  550  performs key management by generating a new key every time a node joins a channel and by generating a new key every time a node leaves a channel. There is one KMS per channel in a Supernet. 
     To configure a Supernet, a system administrator creates a configuration file  558  that is used by SASD  540  when starting or reconfiguring a Supernet. This file may specify: (1) the Supernet name, (2) all of the channels in the Supernet, (3) the nodes that communicate over each channel, (4) the address of the KMS for each channel, (5) the address of the VARPD that acts as the server for the Supernet, (6) the user IDs of the users who are authorized to create Supernet nodes, (7) the authentication mechanism to use for each user of each channel, and (8) the encryption algorithm to use for each channel. Although the configuration information is described as being stored in a configuration file, one skilled in the art will appreciate that this information may be retrieved from other sources, such as databases or interactive configurations. 
     After the configuration file is created, it is used to start a Supernet. For example, when starting a Supernet, the system administrator first starts SASD, which reads the configuration information stored in the configuration file. Then, the administrator starts the VARPD on the administrator&#39;s machine, indicating that it will act as the server for the Supernet and also starts the KMS process. After this processing has completed, the Supernet is ready for nodes to join it. 
     Memory  502  of device  302  contains SNlogin script  522 , SNlogout script  524 , VARPD  526 , KMC  528 , KMD  530 , and node A  522 , all running in user mode. Memory  502  also includes TCP/IP protocol stack  534  and VARPDB  536  running in kernel mode. 
     SNlogin  522  is a script used for logging into a Supernet. Successfully executing this script results in a Unix shell from which programs (e.g., node A  522 ) can be started to run within the Supernet context, such that address translation and security encapsulation is performed transparently for them and all they can typically access is other nodes on the Supernet. Alternatively, a parameter may be passed into SNlogin  522  that indicates a particular process to be automatically run in a Supernet context. Once a program is running in a Supernet context, all programs spawned by that program also run in the Supernet context, unless explicitly stated otherwise. SNlogout  524  is a script used for logging out of a Supernet. Although both SNlogin  522  and SNlogout  524  are described as being scripts, one skilled in the art will appreciate that their processing may be performed by another form of software. VARPD  526  performs address translation between node IDs and real addresses. KMC  528  is the key management component for each node that receives updates whenever the key for a channel (“the channel key”) changes. There is one KMC per node per channel. KMD  530  receives requests from SNSL  542  of the TCP/IP protocol stack  534  when a packet is received and accesses the appropriate KMC for the destination node to retrieve the appropriate key to decrypt the packet. Node A  532  is a Supernet node running in a Supernet context. 
     TCP/IP protocol stack  534  contains a standard TCP/UDP layer  538 , two standard IP layers (an inner IP layer  540  and an outer IP layer  544 ), and a Supernet security layer (SNSL)  542 , acting as the conduit for all Supernet communications. To conserve memory, both inner IP layer  540  and outer IP layer  544  may share the same instance of the code of an IP layer. SNSL  542  performs security functionality as well as address translation. It also caches the most recently used channel keys for ten seconds. Thus, when a channel key is needed, SNSL  542  checks its cache first, and if it is not found, it requests KMD  530  to contact the appropriate KMC to retrieve the appropriate channel key. Two IP layers  540 ,  544  are used in the TCP/IP protocol stack  534  because both the internal addressing scheme and the external addressing scheme are IP-based. Thus, for example, when a packet is sent, inner IP layer  540  receives the packet from TCP/UDP layer  538  and processes the packet with its node ID address before passing it to the SNSL layer  542 , which encrypts it, prepends the real source IP address and the real destination IP address, and then passes the encrypted packet to outer IP layer  544  for sending to the destination. 
     SNSL  542  utilizes VARPDB  536  to perform address translation. VARPDB stores all of the address mappings encountered thus far by SNSL  542 . If SNSL  542  requests a mapping that VARPDB  536  does not have, VARPDB communicates with the VARPD  526  on the local machine to obtain the mapping. VARPD  526  will then contact the VARPD that acts as the server for this particular Supernet to obtain it. 
     Although aspects of the present invention are described as being stored in memory, one skilled in the art will appreciate that these aspects can also be stored on or read from other types of computer-readable media, such as secondary storage devices, like hard disks, floppy disks, or CD-ROM; a carrier wave from a network, such as the Internet; or other forms of RAM or ROM either currently known or later developed. Additionally, although a number of the software components are described as being located on the same machine, one skilled in the art will appreciate that these components may be distributed over a number of machines. 
       FIGS. 6A and 6B  depict a flow chart of the steps performed when a node joins a Supernet. The first step performed is that the user invokes the SNlogin script and enters the Supernet name, their user ID, their password, and a requested virtual address (step  602 ). Of course, this information depends on the particular authentication mechanism used. Upon receiving this information, the SNlogin script performs a handshaking with SASD to authenticate this information. In this step, the user may request a particular virtual address to be used, or alternatively, the SASD may select one for them. Next, if any of the information in step  602  is not validated by SASD (step  604 ), processing ends. Otherwise, upon successful authentication, SASD creates an address mapping between a node ID and the real address (step  606 ). In this step, SASD concatenates the Supernet ID with the virtual address to create the node ID, obtains the real address of the SNlogin script by querying network services in a well-known manner, and then registers this information with the VARPD that acts as the server for this Supernet. This VARPD is identified in the configuration file. If the node uses multiple channels to communicate, SASD sends the address mapping to the VARPD that acts as a server for that Supernet. 
     After creating the address mapping, SASD informs the KMS that there is a new Supernet member that has been authenticated and admitted (step  608 ). In this step, SASD sends the node ID and the real address to KMS who then generates a key ID, a key for use in communicating between the node&#39;s KMC and the KMS (“a node key”), and updates the channel key for use in encrypting traffic on this particular channel (step  610 ). Additionally, KMS sends the key ID and the node key to SASD and distributes the channel key to all KMCs on the channel as a new key because a node has just been added to the channel. SASD receives the key ID and the node key from KMS and returns it to SNlogin (step  612 ). After receiving the key ID and the node key from SASD, SNlogin starts a KMC for this node and transmits to the KMC the node ID, the key ID, the node key, the address of the VARPD that acts as the server for this Supernet, and the address of KMS (step  614 ). The KMC then registers with the KMD indicating the node it is associated with, and KMC registers with KMS for key updates (step  616 ). When registering with KMS, KMC provides its address so that it can receive updates to the channel key via the Versakey protocol. The Versakey protocol is described in greater detail in  IEEE Journal on Selected Areas in Communication , Vol. 17, No. 9, 1999, pp. 1614-1631. After registration, the KMC will receive key updates whenever a channel key changes on one of the channels that the node communicates over. 
     Next, SNlogin configures SNSL (step  618  in  FIG. 6B ). In this step, SNlogin indicates which encryption algorithm to use for this channel and which authentication algorithm to use, both of which are received from the configuration file via SASD. SNSL stores this information in an access control list. In accordance with methods and systems consistent with present invention, any of a number of well-known encryption algorithms may be used, including the Data Encryption Standard (DES), Triple-DES, the International Data Encryption Algorithm (IDEA), and the Advanced Encryption Standard (AES). Also, RC2, RC4, and RC5 from RSA Incorporated may be used as well as Blowfish from Counterpane.com. Additionally, in accordance with methods and systems consistent with the present invention, any of a number of well-known authentication algorithms may be used, including Digital Signatures, Kerberos, Secure Socket Layer (SSL), and MD5, which is described in RFC1321 of the Internet Engineering Task Force, April, 1992. 
     After configuring SNSL, SNlogin invokes an operating system call, SETVIN, to cause the SNlogin script to run in a Supernet context (step  620 ). In Unix, each process has a data structure known as the “proc structure” that contains the process ID as well as a pointer to a virtual memory description of this process.  FIG. 7  depicts a process table  700  that lists all of the proc structures currently executing in memory. The columns  710 ,  720 ,  730 , and  740  show data regarding the attributes of each process. A record  750  includes for each process: a process ID  710 ; a process name  720 ; a Supernet ID  730  indicating the channel the process belongs; and vaddr  740  indicating the virtual address for the node. One skilled in the art will appreciate that process table  700  may contain additional information to maintain the process. To join multiple Supernets, the user repeats the steps of  FIGS. 6A and 6B  for each Supernet. 
     In accordance with methods and systems consistent with the present invention, the IDs indicating the channels over which the process communicates as well as its virtual address for this process are added to this structure. By associating this information with the process in process table  700 , the SNSL layer can enforce that this process runs in a Supernet context. Also during step  620 , a gateway may be initiated to communicate across multiple channels. To do so, SNlogin executes a gateway process that spawns two child processes, both of which are connected by a shared-memory region in memory. Each child process connects one channel to the shared gateway process. Alternatively, Snlogin may execute a “privileged process” that determines which channels belongs in the gateway. The privileged process is capable of connecting any channel and is created by a user with access to all channels (e.g., a superuser). This process forwards information from a first socket to a second socket within an address space of the privileged process to establish the gateway. Although methods and systems consistent with the present invention are described as operating in a Unix environment, one skilled in the art will appreciate that such methods and systems can operate in other environments. After the SNlogin script runs in the Supernet context, the SNlogin script spawns a Unix program, such as a Unix shell or a service daemon (step  622 ). In this step, the SNlogin script spawns a Unix shell from which programs can be run by the user. All of these programs will thus run in the Supernet context until the user runs the SNlogout script. 
       FIG. 8  depicts a flow chart of the steps performed when sending a packet from node A. Although the steps of the flow chart are described in a particular order, one skilled in the art will appreciate that these steps may be performed in a different order. Additionally, although the SNSL layer is described as performing both authentication and encryption, this processing is policy driven such that either authentication, encryption, both, or neither may be performed. The first step performed is for SNSL layer  542  to receive a packet originating from node A via the TCP/UDP layer and the inner IP layer  540  (step  802 ). The packet contains a source node ID, a destination node ID, and data. The packet may be received from a process executing in node A connected to a socket. A socket is a well-known software object that connects an application to a network protocol. In UNIX, for example, an application can send and receive TCP/IP messages by opening a socket and reading and writing data to and from the socket. When the packet is received, a Supernet ID and virtual address are appended to a socket structure. The socket structure is modified so as to contain an extra data field for the Supernet ID and virtual address. The addition of a Supernet ID and virtual address in the socket structure enables the Supernet to provide flexible security at a socket level, process level, or node level since the socket structure can discard packets when the sending application/node/process is prohibited from using that channel. Therefore, when a process executing on node A opens a socket to transmit the packet to SNSL layer  542  (step  802 ), the corresponding Supernet ID and virtual address for that process are also included in the socket request. 
     The SNSL layer then accesses the VARPDB to obtain the address mapping between the source node ID and the source real address as well as the destination node ID and the destination real address (step  804 ). If they are not contained in the VARPDB because this is the first time a packet has been sent from this node or sent to this destination, the VARPDB accesses the local VARPD to obtain the mapping. When contacted, the VARPD on the local machine contacts the VARPD that acts as the server for the Supernet to obtain the appropriate address mapping. 
     After obtaining the address mapping, the SNSL layer determines whether it has been configured to communicate over the appropriate channel for this packet (step  706 ). This configuration occurs when SNlogin runs, and if the SNSL has not been so configured, processing ends. Otherwise, SNSL obtains the channel key to be used for this channel (step  808 ). The SNSL maintains a local cache of keys and an indication of the channel to which each key is associated. Each channel key is time stamped to expire in ten seconds, although this time is configurable by the administrator. If there is a key located in the cache for this channel, SNSL obtains the key. Otherwise, SNSL accesses KMD which then locates the appropriate channel key from the appropriate KMC. After obtaining the key, the SNSL layer encrypts the packet using the appropriate encryption algorithm and the key previously obtained (step  810 ). When encrypting the packet, the source node ID, the destination node ID, and the data may be encrypted, but the source and destination real addresses are not, so that the real addresses can be used by the public network infrastructure to send the packet to its destination. 
     After encrypting the packet, the SNSL layer authenticates the sender to verify that it is the bona fide sender and that the packet was not modified in transit (step  812 ). In this step, the SNSL layer uses the MD5 authentication protocol, although one skilled in the art will appreciate that other authentication protocols may be used. Next, the SNSL layer passes the packet to the IP layer where it is then sent to the destination node in accordance with known techniques associated with the IP protocol (step  814 ). 
       FIG. 9  depicts a flow chart of the steps performed by the SNSL layer when it receives a packet. Although the steps of the flow chart are described in a particular order, one skilled in the art will appreciate that these steps may be performed in a different order. Additionally, although the SNSL layer is described as performing both authentication and encryption, this processing is policy driven such that either authentication, encryption, both, or neither may be performed. To decapsulate the packet with the additional information (Supernet ID and virtual address), similar to the sending node, the receiving node uses a modified socket structure. The first step performed by the SNSL layer is to receive a packet from the network (step  901 ). This packet contains a real source address and a real destination address that are not encrypted as well as a source node ID, a destination node ID, and data that are encrypted. Then, it determines whether it has been configured to communicate on this channel to the destination node (step  902 ). If SNSL has not been so configured, processing ends. Otherwise, the SNSL layer obtains the appropriate key as previously described (step  904 ). It then decrypts the packet using this key and the appropriate encryption algorithm (step  906 ). After decrypting the packet, the SNSL layer authenticates the sender and validates the integrity of the packet (step  908 ), and then it passes the packet to the inner IP layer for delivery to the appropriate node (step  910 ). To pass the additional information to the other IP layers, the packet is passed using a modified socket structure, as described above. Upon receiving the packet, the inner IP layer uses the destination node ID to deliver the packet. 
       FIG. 10  depicts a flow chart of the steps performed when logging a node out of a Supernet. The first step performed is for the user to run the SNlogout script and to enter a node ID (step  1002 ). Next, the SNlogout script requests a log out from SASD (step  1004 ). Upon receiving this request, SASD removes the mapping for this node from the VARPD that acts as the server for the Supernet (step  1006 ). SASD then informs KMS to cancel the registration of the node, and KMS terminates this KMC (step  1008 ). Lastly, KMS generates a new channel key for the channels on which the node was communicating (step  1010 ) to reduce the likelihood of an intruder being able to intercept traffic. 
     CONCLUSION 
     Although the present invention has been described with reference to a preferred embodiment, those skilled in the art will know of various changes in form and detail which may be made without departing from the spirit and scope of the present invention as defined in the appended claims and their full scope of equivalents.