Abstract:
In some networking situations, securing an inner packet of a tunnel packet requires an intermediary networking device knowing a destination address of the secured inner packet. Consequently, an identity of a secured network is known to others and presents a security risk. The provided technique addresses this risk by: i) establishing at a first security interface a first secured network connection between a first and second secured network, the connection established for a first packet addressed to a virtual security interface and destined for the second secured network; and ii) responding to a network condition by establishing at a second security interface at least one second secured network connection between the first and second secured network, the connection established for a second packet addressed to the virtual security interface and destined for the second secured network.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Computer network traffic is normally sent unsecured without encryption or strong authentication of the sender and receiver. This allows the traffic to be intercepted, inspected, modified, or redirected. Either the sender or the receiver can falsify their identity. In order to allow private traffic to be sent in a secured manner, a number of security schemes have been proposed and are in use. Some are application dependent, as with a specific program performing password authentication. Others, such as (TLS), are designed to provide comprehensive security to whole classes of traffic such as web pages (e.g., Hypertext Transfer Protocol (HTTP)) and file transfers, e.g., File Transfer Protocol (FTP). 
         [0002]    Internet Security (IPsec) was developed to address a broader security need. As the majority of network traffic today is over Internet Protocol (IP), IPsec was designed to provide encryption and authentication services to this type of traffic regardless of the application or transport protocol. A standard IPsec datagram in tunnel mode can be used to provide Virtual Private Networking (VPN) and other security functions. In standard IPsec tunnel mode processing, the entire content of an original IP packet is encrypted and encapsulated inside another IP packet, namely, an IPsec packet. The IPsec packet is sealed with an Integrity Check Value (ICV) which authenticates a sender and prevents modification of the packet in transit. 
         [0003]    Unlike a standard IP packet or other types of IPsec packets (e.g., transport mode packets), an IPsec tunnel mode packet has its original IP header encapsulated and encrypted as well as its original IP payload. This allows a source and a destination address of the IPsec tunnel mode packet to be different from those of the encapsulated IP packet. This in turn permits a secure IP tunnel to be formed through which the IPsec tunnel packet is routed. 
         [0004]    When the IPsec tunnel mode packet arrives at its destination it goes through an authentication check. The authentication check includes validation of the IPsec tunnel mode packet header, and an authentication of the IP packet. The authentication of the IP packet includes performing a cryptographic hash such as MDS or SHA-1. A mismatched hash value is used to identify whether the IP packet was damaged in transit or whether an improper key was used. When the IPsec header of the IPsec tunnel mode packet is validated, the IPsec header is stripped off and the original IP packet is restored in the clear, including the original header with original source and destination addresses. 
         [0005]    Standard IPsec implementations require IP addresses be included in the ICV. Consequently, any modification (e.g., translation) to an IP address will cause the integrity check to fail when verified by a recipient. Since the ICV incorporates a secret key which is unknown by intermediate networking devices, such as an intermediate router used for network load balancing or resilient routing, in an event such a device modifies an IP address the device is unable to re-compute the ICV. Accordingly, standard IPsec implementations are not compatible with several common networking functions. Such IPsec implementations are limited to networking situations where a source and a destination networks are reachable without modifying an IP address. 
         [0006]    A solution is described in a U.S. Provisional Patent Application No. 60/756,765 entitled SECURING NETWORK TRAFFIC USING DISTRIBUTED KEY GENERATION AND DISSEMINATION OVER SECURE TUNNELS, filed Jan. 6, 2006, assigned to CipherOptics, Inc. This solution overcomes the limitation by copying an IP header of an outgoing packet in an outer header of an IPsec tunnel mode packet. More specifically, an original source IP address and an original destination IP address of an encrypted outgoing packet are copied to the outer header of the IPsec tunnel mode packet. By copying the addresses to the outer header resulting in an IPsec-like packet, there is greater flexibility in handling such a packet. The IPsec-like packet is suited for a number of networking situations previously unsuitable for an IPsec tunnel mode packet. 
         [0007]    For example, in a network situation, such as network load sharing and resilient routing where more than one physical router receives a packet, the packet travels down different network paths and between different internetworking devices. By copying the original source IP address and the original destination IP address of the encrypted outgoing packet copied to the outer header, the IPsec-like packet is routed according to its original addresses. That is, the IPsec-like packet is not exclusively routed according to IPsec tunnel mode addresses of the IPsec tunnel mode packet. 
         [0008]    This solution by its very nature makes a secured network known. There are several instances where it is desirable or even necessary that the secured network is unknown or is otherwise hidden. One such instance is network security. Typically, packets from one secured network to another secured network traverse an unsecured network. Once a packet leaves a secured network and enters into an unsecured network, the packet can be intercepted and inspected, e.g., using a packet analyzer or “sniffer.” Inspecting an IPsec-like packet with a copied source address and a copied destination address reveals identities of both the first secured network and the second secured network. As such, an implementation other than copying an IP header of an outgoing packet to an outer header of an IPsec tunnel mode packet is desirable in terms of providing network security. 
         [0009]    Another such instance is address space conservation. Typically, a secured network has a limited number of available addresses. To conserve addresses, a network secured network uses private addresses. By agreement private addresses are freely usable by any network with the exception that packets addressed with private addresses cannot be routed in a public network, e.g., the Internet. That is to say, the use of private addresses is limited to a private network, e.g., a remote office. As such, an implementation other than copying an IP header of an outgoing packet to an outer header of an IPsec tunnel mode packet is necessary in terms of conserving addresses. 
       SUMMARY OF THE INVENTION 
       [0010]    For purposes of explaining aspects of various embodiments of the present invention, the following terms are defined and used herein: 
         [0011]    “Securing data” (or “traffic”) refers to applying a specific type of encryption and authentication to data. Applying encryption to data involves encrypting data in instances when data is unencrypted or “in the clear”, and de-encrypting data in instances when data is encrypted. 
         [0012]    “Secured data” (or “traffic”) refers to data secured by the application of a specific type of encryption and authentication. In some instances, secured data refers to encrypted and authenticated data, e.g., data traversing an unsecured network. In other instances, secured data refers to unencrypted and unauthenticated data, e.g., data in a secured network. 
         [0013]    A “secure tunnel” between two devices ensures that data passing between the two devices is secured. 
         [0014]    A “secured network” is a network in which data to and from the network is secured. 
         [0015]    A “security policy” (or simply “policy”) for a secure tunnel defines data (or “traffic”) to be secured by a source IP address, a destination IP address, a port number and/or a protocol. The security policy also defines a type of security to be performed. 
         [0016]    A “security key” for a secure tunnel is a secret information used to encrypt or to decrypt (or to authenticate and to verify) data in one direction of traffic in the secure tunnel. 
         [0017]    Embodiments of the present invention provide a technique for hiding and securing a network. In one embodiment, the technique comprises of: i) establishing at a first security interface a first secured network connection between a first secured network and a second secured network, the first secured network connection established for a first packet which is addressed to a virtual security interface and which is destined for the second secured network, and ii) responding to a network condition by establishing at a second security interface at least one second secured network connection between the first secured network and the second secured network, the at least one second secured network connection established for a second packet which is addressed to the virtual security interface and which is destined for the second secured network. 
         [0018]    In an alternative embodiment, the technique further comprises of sharing a security policy between the first security interface and the second security interface, the first secured network connection and the at least one second secured network connection established according to the shared security policy. 
         [0019]    In another embodiment, the technique responds to a network condition by offloading a network security burden from a first secured network connection to an at least one second secured network connection. 
         [0020]    In yet another embodiment, the technique responds to a network condition by balancing a network load from a first secured network connection to an at least one second secured network connection. 
         [0021]    In still another embodiment, the technique responds to a network condition by resiliently routing from a first secured network connection to an at least one second secured network connection. 
         [0022]    In an embodiment, the technique establishes a secured network connection between a first secured network and a second secured network by securing a packet addressed to a virtual security interface. 
         [0023]    In another embodiment, the technique secures a packet addressed to a virtual security interface by de-encapsulating and de-encrypting the packet according to a shared security policy. 
         [0024]    In yet another embodiment, the technique establishes a secured network connection between a first secured network and a second secured network by securing a packet addressed from the first secured network. 
         [0025]    In still yet another embodiment, the technique secures a packet addressed from a secured network by encrypting the packet according to a shared security policy and encapsulating the encrypted packet in a tunnel packet, a source of the tunnel packet is a virtual security interface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
           [0027]      FIG. 1  is a network diagram of an example wide area data communications network implementing an embodiment of the present invention; 
           [0028]      FIG. 2  is a block diagram of an example virtual security interface in accordance with an embodiment of the present invention; 
           [0029]      FIG. 3A  is a block diagram illustrating establishing at a security interface a secured network connection between a first secured network and a second secured network in accordance of an embodiment of the present invention; 
           [0030]      FIGS. 3B-3D  are block diagrams illustrating responding to a various network conditions by establishing at a security interface a secured network connection between a first secured network and a second secured network; 
           [0031]      FIG. 4  is a packet diagram illustrating securing a packet sent from an end node on a secured remote network to an end node on a secured local network in accordance with an embodiment of the present invention; 
           [0032]      FIG. 5  is a flow chart for an example process for hiding and securing a network in accordance with an embodiment of the present invention; 
           [0033]      FIG. 6  is a flow chart of an example process processing a packet from a secured remote network in accordance with an embodiment of the present invention; 
           [0034]      FIG. 7  is a flow chart of an example process processing a packet from a secured local network in accordance with an embodiment of the present invention; and 
           [0035]      FIG. 8  is a block diagram of an example security interface in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    A description of preferred embodiments of the invention follows. 
         [0037]      FIG. 1  illustrates an example wide area data communications network  100  implementing an embodiment of the present invention. 
         [0038]    In the network  100  there are secured networks  105   a,    105   b,  and  105   c,  generally  105 . Secured networks  105  may be may be subnets, physical LAN segments or other network architectures. What is important is the secured networks  105  are logically separate from one another and from other secured networks. 
         [0039]    The secured network  105  may be a single office of an enterprise which has only a few computers. In contrast, the secured network  105  may be a large building, complex or campus which has many computers. For example, the secured network  105   a  is in a west coast headquarters office located in Los Angeles and the secured network  105   b  is an east coast sales office located in New York City. 
         [0040]    In the network  100 , there is also an unsecured network  110 . The unsecured network  110  is, for example, the Internet. The network  100  is implemented or otherwise deployed in such a fashion which requires a secure network connection from one secured network (e.g.,  105   a ) to another secured network (e.g.,  105   b ) to traverse an unsecured network, e.g.,  110 . One or more tunnels are used to traverse an unsecured network (discussed in greater detail below). 
         [0041]    Continuing with  FIG. 1 , the secured networks  105  and unsecured network  110  are networked together with inter-network devices  115   a,    115   b,    115   c,    115   d,    115   e,  and  115   f,  generally  115 . The inter-network devices  115  are, for example, routers or switches. On the secured network  105  are end nodes  120   a,    120   b,  and  120   c,  generally  120 . The end nodes  120  may be typical client computers, such as Personal Computers (PCs), workstations, Personal Digital Assistants (PDAs), digital mobile telephones, wireless network enabled devices and the like. Additionally, the end nodes  120  may also be file servers, video set top boxes, other data processing machines, or indeed any other device capable of being networked from which messages are originated and to which message are destined. 
         [0042]    Communications between the end nodes  120  typically take the form of data packets in the well known Internet Protocol (IP) packet format. As is well known in the art, an IP packet may be encapsulated by other networking protocols such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), or other lower level and higher level networking protocols. 
         [0043]    Still referring to  FIG. 1 , in the network  100 , a [P] [A] Management System (PAMS) function  125  and a Key Authority Point (KAP) function  130 , and Policy Enforcement Points (PEPs)  135   a,    135   b,    135   c,  and  135   d,  generally  135 , secure data packets to and from the end nodes  120  according to security policies. 
         [0044]    Recall a security policy (or simply a “policy”) defines data packets (or “traffic”) to be secured by a source IP address, a destination IP address, a port number and/or a protocol. The security policy also defines a type of security to be performed on the traffic. 
         [0045]    The PAMS function  125  is used by an administrative user (e.g., a network administrator) to input and configure security policies. Additionally, the PAMS function  125  stores and provides access to security policies used by other elements or functions of the network  100 . 
         [0046]    The KAP function  130  generates and distributes “secret data” known as a security keys to the PEPs  135 . Further details of a preferred embodiment for generating and distributing security keys are contained in a co-pending U.S. Provisional Patent Application No. 60/756,765 entitled SECURING NETWORK TRAFFIC USING DISTRIBUTED KEY GENERATION AND DISSEMINATION OVER SECURE TUNNELS, filed Jan. 6, 2006, assigned to CipherOptics, Inc., and which is hereby incorporated by reference in its entirety. 
         [0047]    The PEP function  135  enforces security policies. According to a security policy, the PEP function  135  secures or otherwise establishes a secured network connection to a secured network. In this way, the PEP function  135  acts as an security interface to the secured network. Presently different, packets destined to the secured network are sent through the PEP function  135 . Likewise, packets sourced from the secured network are sent through the PEP function  135 . 
         [0048]      FIG. 1  illustrates the network  100  has having a single PAMS function (e.g.,  125 ) and a single KAP function (e.g.,  130 ) immediately networked to the secured network  105   a.  One skilled in the art, however, will readily recognize the network configuration of network  100  is merely an example and other network configurations are within the contemplation the present invention. For example, in another example network there are more than one PAMS function and more than one KAP function distributed throughout a network and coordinated by a central function(s). 
         [0049]    Continuing with  FIG. 1 , packets between the secured networks  105   a  and  105   b  are secured by the PEPs  135   b  and  135   c  (PEP-B and PEP-C, respectively). Recall securing implies both encrypting data in transit and authenticating that data to ensure that the data has not been manipulated in transit. For purposes of explaining aspects of embodiments of the present invention, the secured network  105   a  is referred to hereinafter as a secured remote network and the secured network  105   b  is referred to hereinafter as a secured local network. In this way, the PEPs  135   b  and  135   c  are said to have an interface (not shown) to a secured remote network (e.g.,  105   a ) and an interface (not shown) to the secured local network  105   b.    
         [0050]    The interfaces to a secured local network are represented as a virtual security interface  140 . The virtual security interface  140  is not a physical interface, but rather a logical interface. As such, and as will be described in greater detail below, the virtual security interface  140  represents a plurality of interfaces to a secured local network. 
         [0051]      FIG. 2  further illustrates the virtual security interface  140  of  FIG. 1 . In  FIG. 2 , there are n number of security interfaces  205   a,    205   b  . . .  205   n  (generally  205 ) to a secured local network  210 . The security interfaces  205  secure or otherwise establish secured network connections between the secured local network  210  and a secured remote network  215 . In particular, the security interfaces  205  secure packets destined for the secured local network  210  which are sent from the secured remote network  215 , and vice versa. 
         [0052]    The virtual security interface  140  logically represents the security interfaces  205 . Packets addressed to the virtual security interface  140  are in reality destined for the security interfaces  205 . The following example illustrates the virtual security interface logically representing the security interfaces  205 . 
         [0053]    From the secured remote network  215 , a packet  220  is sent. The sent packet  220  is addressed to the virtual security interface  140 . Since the packet  220  is addressed to the virtual security interface  140  and not a particular security interface, the packet is destined for any of the security interfaces  205 . In some instances the packet  220  is destined for any number of the security interfaces  205  (described later). Consequently, any of the security interfaces  205  secure the packet  220  resulting in a secured packet  225 . 
         [0054]    By way of example, in  FIG. 2 , the packet  220 , addressed to the virtual security interface  140 , is destined for the security interface  205   a.  The security interface  205   a  secures the sent packet  220  resulting in the secured packet  225 . The broken lines denote the packet  220  being alternatively destined for a security interface other than the security interface  205   a.  As illustrated, the packet  220  destined for the security interface  205   b  is secured by that security interface, and so on. 
         [0055]    An identity, indeed a presence of a secured network is known because of a security interface(s) to the secured network. Hiding the security interface to the secured network effectively hides the secured network. In this way, addressing a packet to a virtual security interface rather than the security interface to the secured network, the identity or presence of the secured network cannot be ascertained by inspecting the packet. As such, the secured network is hidden. 
         [0056]      FIG. 3A  illustrates establishing a first secured network connection at a first security interface. In  FIG. 3A , a packet  305  from a secured remote network  310  is addressed to a virtual security interface  315 . As previously described, packets addressed to a virtual security interface are secured by any security interface and any number of security interfaces. Since packets are addressed to the virtual security interface and not a particular security interface, it appears to an end node in the secured remote network  310  that a secured network connection is established at the virtual security interface. In actuality, one or more secured network connections between the secured remote network  310  and the secured local network  330  are established at the one or more security interfaces. In other words, the secured network connections actually established are transparent or otherwise hidden from an end node. More significantly, these connections are hidden from others in a network. 
         [0057]    By way of example, in  FIG. 3A , the packet  305 , while addressed to the virtual security interface  315 , is secured by a security interface  320 . At the security interface  320 , a first secured network connection between the secured remote network  310  and the secured local network  330  is established according to a security policy. The security policy states or otherwise defines a specific type of encryption and authentication to apply to packets between the secured remote network  310  and secured local network  330 . The packet  305  is sent from the secured remote network  310  to the secured local network  330  using the established first secured network connection. 
         [0058]    Securing the packet  305  results in a secured packet  306  destined for the secured local network  330 . In some instances, the secured packet  306  is de-encrypted and authenticated, i.e., the packet is “in the clear.” In other instances, the secured packet  306  is re-secured (e.g., re-encrypted) according to another security policy. While  FIG. 3A  illustrates establishing a single secured network connection between a secured remote network and a secured local network, there are several instances where more than one secured network connections are established. 
         [0059]      FIGS. 3B-3D  illustrate various examples of responding to a network condition by establishing at least one second secured network connection. In  FIG. 3B , packets  1305   a  and  1305   b  from a secured remote network  1310  are addressed to a virtual security interface  1315 . The packet  1305   a  is secured by a first security interface  1320   a.    
         [0060]    At the first security interface  1320   a,  a first secured network connection between the secured remote network  1310  and a secured local network  1330  is established according to a security policy. The security policy states or otherwise defines a specific type of encryption and authentication to apply to packets between the secured remote network  1310  and the secured local network  1330 . Using the established first secured network connection, the packet  1305   a  is sent from the secured remote network  1310  to the secured local network  1330 . A secured packet  1306   a  is received by the secured local network  1330 . 
         [0061]    The packet  1305   b,  however, is not secured by the first security interface  1320   a.  In this example, the first security interface  1320   a  is busy securing the packet  1305   a  and is unable to secure additional packets. That is to say, the first security interface  1320   a  is overloaded or otherwise overburdened with providing security. In order to offload or otherwise alleviate this burden, the packet  1305   b  is secured by a second security interface  1320   b.    
         [0062]    At the second security interface  1320   b,  a second secured network connection between the secured remote network  1310  and the secured local network  1330  is established according to a security policy. The security policy states or otherwise defines a specific type of encryption and authentication to apply to packets between the secured remote network  1310  and secured local network  1330 . Using the established second secured network connection, the packet  1305   b  is sent from the secured remote network  1310  to the secured local network  1330 . A secured packet  1306   b  is received by the secured local network  1330 . 
         [0063]    In this way, an at least one second secured network connection is established in response to a network security overload condition. Presently differently, an at least second secured network connection is established to offload a network security burden from one security interface (e.g., the first security interface  1320   a ) to another security interface, e.g., the second security interface  1320   b.    
         [0064]    In  FIG. 3C , packets  2305   a  and  2305   b  from a secured remote network  2310  are addressed to a virtual security interface  2315 . The packet  2305   a  is secured by a first security interface  2320   a.  At the first security interface  2320   a,  a first secured network connection  2325   a  is established between the secured remote network  2310  and a secured local network  2330  according to a security policy. The security policy states or otherwise defines a specific type of encryption and authentication to apply to packets between the secured remote network  2310  and secured local network  2330 . Using the established first secured network connection, the packet  2305   a  is sent from the secured remote network  2310  to the secured local network  2330 . A secured packet  2306   a  is received by an end node-A  2328   a  on the secured local network  2330 . 
         [0065]    The packet  2305   b,  however, is not secured by the first security interface  2320   a.  In this example, in contrast to packet  2305   a,  the packet  2305   b  is to be handled or otherwise processed not by the end node-A  2328   a,  but by an end node-B  2328   b  on the secured local network  2230 . In other words, packets are not necessarily processed by a single end node, but be processed by additional end nodes. 
         [0066]    In one instance, packets are processed by different end nodes depending on a type or a protocol of a packet. For example, a Hypertext Transport Protocol (HTTP) packet (e.g., a HTTP GET) is processed by an HTTP server, while a File Transfer Protocol (FTP) packet (e.g., a FTP PUT) is processed by an FTP server. In another instance, packets are processed by different end nodes in an event one end node is overloaded or otherwise burden and unable to process additional packets. In either case, network loads of two of more end nodes are balanced. 
         [0067]    In order to balance network loads, the packet  2305   b  is secured by a second security interface  2320   b.  At the second security interface  2320   b,  a second secured network connection  2325   b  between the secured remote network  2310  and the secured remote network  2330  is established according to a security policy. The security policy states or otherwise defines a specific type of encryption and authentication to apply to packets between the secured remote network  2310  and secured local network  2330 . Using the established second secured network connection, the packet  2305   b  is sent from the secured remote network  2310  to the secured local network  2330 . A secured packet  2306   b  is received by an end node-B  2328   b  on the secured local network  2330 . 
         [0068]    In this way, an at least one second secured network connection is established in response to a network load balancing condition. Presently differently, an at least one second secured network connection is established to balance a network load of one end node (e.g., the end node-A  2328   a ) with a network load of another end node, e.g., the end node-B-A  2328   b.    
         [0069]    In  FIG. 3D , packets  3305   a  and  3305   b  from a secured remote network  3310  are addressed to a virtual security interface  3315 . The packet  3305   a  is secured by a first security interface  3320   a.  At the first security interface  3320   a,  a first secured network connection  3325   a  between the secured remote network  3310  and a secured local network  3330  is established according to a security policy. The security policy states or otherwise defines a specific type of encryption and authentication to apply to packets between the secured remote network  3310  and secured local network  3330 . Using the established first secured network connection, the packet  3305   a  is sent from the secured remote network  3310  to the secured local network  3330 . A secured packet  3306   a  is received by the secured local network  3330 . 
         [0070]    The packet  3305   b,  however, is not secured by the first security interface  3320   a.  In this example, the first security interface  3320   a  is malfunctioning or otherwise incapable of securing additional packets (denoted in  FIG. 3D  by broken lines). To prevent losing a packet, the packet  3305   b  is secured by a second security interface  3320   b.  At the second security interface  3320   b,  a second secured network connection  3325   b  between the secured remote network  3310  and the secured local network  3330  is established according to a security policy. The security policy states or otherwise defines a specific type of encryption and authentication to apply to packets between the secured remote network  1310  and secured local network  1330 . Using the established second secured network connection, the packet  3305   b  is sent from the secured remote network  3310  to the secured local network  3330 . A secured packet  3306   b  is received by the secured local network  3330 . 
         [0071]    In this way, an at least one second secured network connection is established in response to a network failover condition. Presently differently, an at least second secured network connection is established to resiliently route from one security interface (e.g., the first security interface  3320   a ) to another security interface, e.g., the second security interface  3320   b.    
         [0072]      FIG. 4 , an end node-A  405  on a secured remote network sends an Internet Protocol (IP) packet  410  to an end node-B  415  on a secured local network. The IP packet  410  has at least an IP header  411  and an IP payload  412 . The IP header  411  has at least a source IP address of the end node-A  405  and a destination IP address of the end node-B  415 . The IP packet  410  is secured by a security interface-A  420  according to a security policy. The security policy states or otherwise defines that data between a secured remote network and secured local network is to be secured by a specific type of encryption and authentication. The IP packet  410  is encrypted and encapsulated inside an IP tunnel packet  425 . The IP tunnel packet  425  has at least an IP tunnel header  426  and an encrypted payload  427 . The IP tunnel header  426  has at least a tunnel source IP address of the security interface-A  420  and a tunnel destination IP address of a virtual security interface (not shown). 
         [0073]    In order for the security interface-A  420  to send the IP tunnel packet  425  to the virtual security interface, a physical layer address of the virtual security interface must be resolved. This is accomplished, for example, with the well-known Ethernet Address Resolution Protocol (ARP). See Request For Comments (RFC)  826 . The security interface-A  420  broadcasts an ARP-request  435  asking for a physical layer address of the virtual security interface. Recall, the virtual security interface is not a physical interface, but a logical representation of one or more security interfaces to a secured local network. See  FIG. 1 . As such, the ARP-request  435  may be answered with a physical address of one of several security interfaces. 
         [0074]    By way of example, in  FIG. 4 , the virtual security interface logically represents a security interface-B 1   430   a  and a security interface-B 2   430   b.  The security interface-B 1   430   a  and the security interface-B 2   430   b,  however, do not answer to the ARP-request  435 . That is to say, the ARP-request  435  is “transparent” to the security interface-B 1   430   a  and the security interface-B 2   430   b,  and “passes through” the security interface-B 1   403   a  and the security interface-B 2   430   b.  In this example, the ARP-request  435  is answered by a proxy  440 . The proxy  440  may be a network device (e.g., a router), a computer or for that matter any device or process capable for answering an ARP-request with a physical address which is not its own. In this example, the proxy  440  answers with an ARP-response  445  providing a physical address of the security interface-B 2   430   b.  The proxy  440  could have answered with a physical address of the security interface-B 1   430   a.  The physical address with which the proxy  440  actually answers with is not of importance. What is of significance, however, is an ARP-request for a physical address of a virtual security interface is answered with an ARP-response with a physical address of a security interface to a secured local network. 
         [0075]    Continuing with  FIG. 4 , in this example, the address of the virtual security interface is resolved to the physical address of the security interface-B 2   430   b.  Consequently, the IP tunnel packet  425  is secured by the security interface-B 2   430   b  and not the security interface-B 1   430   a.  Note, in an event the virtual security interface is resolved to the physical address of the security interface-B 1   430   a,  the IP tunnel packet  425  is secured by the security interface-B 1   430   a  and not the security interface-B 2   430   b.  Resuming the prior example, the security interface-B 2   430   b  de-encapsulates the IP tunnel packet  425  by stripping off or otherwise removing the IP tunnel header  426 . The security interface-B 2   430   b  de-encrypts the encrypted payload  427 . With the IP tunnel packet  425  de-encapsulated and de-encrypted, a secured IP packet  445  is destined for the end node-B  415 . 
         [0076]      FIG. 5  illustrates an example process  500  for hiding and securing a network. The process  500  establishes ( 505 ) a first secured network connection between a first secured network and a second secured network. The first secured network connection is established for a first packet which is addressed to a virtual security interface and which is destined for the second secured network. 
         [0077]    The process  500  responds ( 510 ) to a network condition by establishing at least one second secured network connection between the first secured network and the second secured network. The at least one second secured network connection is established for a second packet which is addressed to the virtual security interface and which is destined for the second secured network. 
         [0078]      FIG. 6  illustrates an example process  600  processing a packet from a secured remote network. The process  600  determines ( 605 ) whether the packet is a tunnel IP packet. If the process  600  determines ( 605 ) the packet is a tunnel IP packet, then the process  600  determines ( 610 ) whether the tunnel destination of the tunnel IP packet is a virtual security interface. 
         [0079]    In an embodiment, the process  600  is configured with at least one security policy (not shown). The security policy indicates using an IP address of a virtual security interface for selectors associated with a packet. The security policy dictates an action to take with respect to a packet. For example, a packet is accepted for further processing, passed through without further processing or dropped. In this way, according to a security policy, whether a packet is addressed with the IP address of the virtual security interface determines whether a packet is further processed, is not further processed or is simply dropped. 
         [0080]    In an alternative embodiment having more than one process  600 , the security policy indicating using an IP address of a virtual security interface for selectors associated with packets, is distributed or otherwise disseminated to each process  600 . Further details of a preferred embodiment for distributing security polices are contained in a co-pending U.S. Provisional Patent Application No. 60/813,766 entitled SECURING NETWORK TRAFFIC BY DISTRIBUTING POLICIES IN A HIERARCHY OVER SECURE TUNNELS, filed Jun. 14, 2006, assigned to CipherOptics, Inc., and which is hereby incorporated by reference in its entirety. 
         [0081]    Retuning to  FIG. 6 , if the process  600  determines ( 610 ) that the tunnel destination of the tunnel IP packet is a virtual security interface, then the process  600  de-encapsulates ( 620 ) the packet. As described earlier in reference to  FIG. 4 , de-encapsulating a tunnel IP packet involves at least removing a tunnel IP header from a tunnel IP packet. The process  600  de-encrypts ( 630 ) the packet with a security key according to a security policy. 
         [0082]    Recall, a security key is secret information used to encrypt or to de-encrypt data. In an embodiment having more than one process  600 , the security key is distributed or otherwise disseminated to each process  600 . Further details of a preferred embodiment for distributing security keys are contained in a co-pending U.S. Provisional Patent Application No. 60/756,765 entitled SECURING NETWORK TRAFFIC USING DISTRIBUTED KEY GENERATION AND DISSEMINATION OVER SECURE TUNNELS, filed Jan. 6, 2006, assigned to CipherOptics, Inc., and which is hereby incorporated by reference in its entirety. 
         [0083]    Returning to the process  600 , if the process  600  determines ( 605 ) the packet is not a tunnel IP packet (e.g., the ARP-request of  FIG. 4 ), then the process  600  does not further process ( 615 ) the packet. In some instances, such as the one described in reference to  FIG. 4 , packets are transparent to the process  600 . Presently differently, the process  600  is transparent to certain packet exchanges. 
         [0084]    Returning to the process  600 , if the process  600  determines ( 610 ) a tunnel destination of the tunnel IP packet is not a virtual security interface, then the process  600  drops ( 625 ) the packet. 
         [0085]      FIG. 7  illustrates an example process  700  processing a packet from a secured local network. The process  700  encrypts ( 705 ) the packet using a security key according to a security policy. Recall, a security key is secret information used to encrypt or to de-encrypt data. In an embodiment having more than one process  700 , the security key is distributed or otherwise disseminated to each process  700 . Further details of a preferred embodiment for distributing security keys are contained in a co-pending U.S. Provisional Patent Application No. 60/756,765 entitled SECURING NETWORK TRAFFIC USING DISTRIBUTED KEY GENERATION AND DISSEMINATION OVER SECURE TUNNELS, filed Jan. 6, 2006, assigned to CipherOptics, Inc., and which is hereby incorporated by reference in its entirety. 
         [0086]    Returning to  FIG. 7 , the process  700  encapsulates ( 710 ) the packet inside a tunnel IP packet according to a security policy. The tunnel IP packet has a tunnel source of a virtual security interface. In an embodiment of the present invention, the process  700  is configured with at least one security policy (not shown). The security policy indicates using an IP address of a virtual security interface as a tunnel source of the tunnel IP packet. 
         [0087]    In an alternative embodiment having more than one process  700 , a security policy indicating using an IP address of a virtual security interface as a tunnel source, is distributed or otherwise disseminated to each process  700 . Further details of a preferred embodiment for distributing security polices are contained in a co-pending U.S. Provisional Patent Application No. 60/813,766 entitled SECURING NETWORK TRAFFIC BY DISTRIBUTING POLICIES IN A HIERARCHY OVER SECURE TUNNELS, filed Jun. 14, 2006, assigned to CipherOptics, Inc., and which is hereby incorporated by reference in its entirety. 
         [0088]      FIG. 8  illustrates an example security interface  800  with a de-encapsulator  805 , a de-encryptor  810 , an encapsulator  815  and an encryptor  820 . The security interface  800  also includes an authenticator (not shown). From a first secured network  825 , a tunnel packet  830  is sent. The tunnel packet  830  is addressed to a virtual security interface (not shown). The security interface  800 , however, handles or otherwise processes the tunnel packet  830 . The de-encapsulator  805  removes a tunnel header addressed to the virtual security interface. The authenticator authenticates the resulting de-encapsulated packet. The de-encryptor  810  de-encrypts the authenticated packet, resulting in a secured packet  835 . The secured packet  835  is sent to a second secured network  840 . 
         [0089]    From the second secured network  840 , a packet  845  is sent. The packet  845  is addressed from an end node in the second secured network  840 . The security interface  800  handles or otherwise processes the packet  845 . The encryptor  820  encrypts the packet  845 . The authenticator authenticates the resulting encrypted packet. The encapsulator  815  adds a tunnel header addressed from the virtual security interface, resulting in a secured packet  850 . The secured packet  850  is sent to the first secured network  825 .