RELATED APPLICATION [0001] This Application is related to U.S. Patent Application No. TBD3 entitled "Cooperative Embedded Agents," and filed concurrently herewith.

FIELD [0002] Embodiments of the invention relate cryptography and specifically to sharing of a cryptographic key among multiple clients.

BACKGROUND [0003] Current cryptographic techniques used for encryption of network traffic employ key distribution protocols capable of getting private keys to the endpoints desiring to engage in secure communication. Alternately, these private keys are distributed to the endpoints in advance of the secure communication by some other means (e.g., delivery service, in person, electronically, etc.). When an endpoint is a personal computing device, the keys are typically stored on a hard drive or other persistent storage device and are accessible to the operating system. This potentially makes the keys accessible to applications running on the operating system. Keys stored in this fashion can be accessed by an attacker who successfully compromises the operating system. [0004] In groups of networked endpoints, when one endpoint is compromised, the lack of security of the keys used for secure communication can potentially lead to compromise of other endpoints on the network. Another potentially more serious problem is the ability of the compromising agent (hacker, virus, etc.) to obtain the keys that may be later used to obtain and decrypt data from the secure communication channels. Thus, compromise of a system may lead to loss of cryptographic keys that could lead to loss of secure communication with those keys. [0005] Other problems associated with the keys associated with secure communication among endpoints in a network are potential difficulties with management and distribution. From a management standpoint, the storing and verifying of keys can become a difficult task as the number of endpoints in a network domain grows. Where a network device, such as a switch or firewall, may be able to manage keys for each client to which it is connected, as the number grows, the limited resources in terms of memory and computational resources of the network device may prevent the device from being able to manage keys for all connected endpoints. From a distribution standpoint, there may be difficulty in provisioning keys and keeping track of who has what keys, when keys should be changed, etc.

BRIEF DESCRIPTION OF THE DRAWINGS [0006] The description of embodiments of the invention includes various illustrations by way of example, and not by way of limitation in the figures and accompanying drawings, in which like reference numerals refer to similar elements. [0007] Figure 1 is one embodiment of a block diagram of a network system with clients sharing a cryptographic key. [0008] Figure 2 is one embodiment of a block diagram of a client having a secure storage and an embedded agent. [0009] Figure 3 is one embodiment of a block diagram of a network endpoint device. [0010] Figure 4 is one embodiment of a block diagram of elements of a network endpoint device. [0011] Figure 5 is one embodiment of a flow diagram of accessing a traffic flow with a shared cryptographic key. [0012] Figure 6 is one embodiment of a block diagram of use of an infrastructure device with endpoints having embedded agents for sharing a cryptographic key.

DETAILED DESCRIPTION [0013] Methods and apparatuses associated with sharing cryptographic keys among multiple network devices. A shared cryptographic key is provisioned to multiple devices to use in secure communication. Thus, each device will use the same shared key to engage in secure communication. In one embodiment a shared key is provisioned to clients of a virtual network. The private key identifies the client as a trusted device in the network, and enables the device to securely communicate with endpoints in the network. [0014] The shared cryptographic key is managed in a client by an embedded agent. The embedded agent operates independently of a platform on the client host device. A secure storage is used to store the key, and is accessible by the embedded agent, but not the host operating system. The shared key is thus kept secret from the host operating system. [0015] Figure 1 is one embodiment of a block diagram of a network system with clients sharing a cryptographic key. Virtual private group (VPG) 110 represents endpoints of a network that share a cryptographic key. As illustrated, client 120 and client 130 use a common cryptographic key to encrypt/decrypt secure data for communication over network 140 with server 150. [0016] Clients 120 and 130 include a combination of logic and processor(s). Some of the hardware may include embedded code (firmware) that is stored on and run on the hardware. Also, clients 120 and 130 include user interfaces allowing a user to interact with client 120 and/or client 130. Clients 120 and 130 will include an operating system (OS), that is the main code used to control the flow of execution and instruction on clients 120 and 130. The OS may include e.g., Windows® operating systems from Microsoft® Corporation, Linux, etc. The OS will typically be stored in a persistent storage (e.g., a hard drive) and initialized with boot-up of the client systems. The OS provides user interface to client 120 and/or 130, and allows an environment on which applications may be executed by the systems. The hardware, firmware, and software aspects of a client 120 or 130 are to be understood as being the platform of the client. [0017] Client 120 is shown with embedded agent (EA) 121, and client 130 is shown with EA 131. Embedded agents 121 and 131 represent embedded systems on clients 120 and 130, respectively, that receive and manage the shared key. In one embodiment embedded agents 121 and 131 are systems including embedded processors, a secure key storage, and a cryptographic agent. The cryptographic agent may be implemented in hardware or software running on a device in clients 120 or 130, or a combination of these. The cryptographic agent performs the actual authenticating of data for clients 120 and 130 with the shared key. Authenticating the data with the shared key may include, e.g., hashing the data to authenticate, or sign, it, encrypting the data with the key, placing a derivative of the key in a header associated with the data in transmission. [0018] Embedded agents 121 and 131 may be firmware that is run on a processor on the host system that is independent from the main processor or central processing unit (CPU) of the system. In one embodiment aspects of hardware/firmware that make up embedded agents 121 and 131 are integrated into the same die as a chip or chipset of the platform. [0019] Network 140 is intended to represent any type of network, and may include a variety of network hardware (e.g., routers, switches, firewalls, hubs, traffic monitors, etc.). Each hop 141-143 in network 140 represents one such device. Hop 1 141 may be considered to an aggregation point for network 140, because it aggregates the traffic incoming to network 140 from the clients of VPG 110. Note that while three hops are shown in Figure 1, hop 1 141, hop 2 142, and hop N 143, it is to be understood that there may be more of fewer hops that traffic will take across network 140 from VPG 110 to server 150. In one embodiment network 140 merely consists of the communication line between clients 120 and 130 and server 150; thus, there are zero "hops." [0020] Key distribution 160 represents a trusted network entity to store, distribute, and otherwise manage cryptographic keys for the endpoints and devices of network 140. In one embodiment key distribution 160 maintains a public and private key associated with each endpoint on network 140. Key distribution 160 operates to distribute the shared keys to all systems in a domain sharing cryptographic keys, such as VPG 110. For example, VPG 110 may be considered a network domain because it includes a group of clients associated with each other in one topographical view of network 140. A virtual private network (VPN) may be another example of a domain where a cryptographic key may be shared among multiple endpoints. [0021] In one embodiment key distribution 160 periodically updates the shared key. The periodicity of key changing is dependent on factors such as how susceptible to attempted attack or infection the domain is, the number of client systems in the domain, the burden of key management, etc. For example, key changing may occur once per hour, once daily, once weekly, etc. Key distribution 160 may initiate the updating of the shared key by indicating a change to clients 120 and 130. Alternatively, key distribution may update the key in association with a public/private key exchange with the clients. [0022] Figure 2 is one embodiment of a block diagram of a client having a secure storage and an embedded agent. Virtual private group (VPG) client 200 may be a client from a VPG as described in Figure 1. VPG client 200 includes a host processor 210 that is the main processor in the computational platform of client 200. When client 200 is operational, host processor 210 includes host OS 220 that generally controls the environment of client 200. Host OS 220 is shown with user application threads 221-222, which represent applications and/or threads of applications running on host processor 210. There may be fewer or more user application threads than that shown in Figure 2. [0023] Client 200 includes a platform chipset 230. The platform chipset may include memory hubs and/or controllers, input/output (I/O) hubs and/or controllers, memory subsystems, peripheral controllers, etc. Platform chipset 230 is coupled with host processor 210 by means of one or more communication buses. For example, a peripheral component interconnect (PCI) bus is one common bus in a PC. In alternate embodiments, host processor is coupled with platform chipset 230 by means of a proprietary bus. [0024] In one embodiment platform chipset 230 includes cryptographic (crypto) module 231. Cryptographic module 231 represents hardware (embedded chips, logic, etc.) and/or code running on platform 230 that provides cryptographic services for client 200. In one embodiment hardware cryptographic module 231 may include a Galois counter mode encryption module (GCM) to add another layer of encryption on top of enciphered data. An example algorithm that may be used by a GCM includes Advanced Encryption Standard (AES). [0025] Platform chipset 230 includes crypto engine 232, an embedded agent in client 200. Crypto engine 232 represents a cryptographic control system embedded on platform chipset 230. In one embodiment, crypto engine 232 includes an embedded processor or other computational device that has a direct connection to the network, as shown by communication channel 233. Communication channel 233 may represent one or multiple private communication channels. For example, in one embodiment crypto engine 232 represents multiple embedded agents on client 200, each with a private network access. In a case where multiple private communication channels are used, access may be arbitrated. [0026] Communication channel 233 may represent a channel over the same physical line as network link 234, but communication channel 233 is private to crypto engine 232, and is thus transparent to host processor 210. Thus, host processor 210 may have access to network link 234, but not to communication channel 233. In one embodiment communication channel 233 from crypto engine 232 to the network complies with the transport layer security (TLS) or the secure sockets link (SSL) protocols. Other protocols may include Internet Protocol Security (IPsec) and Wired Equivalent Privacy (WEP). Host processor 210 will have network access through network link 234, including secure communication access. [0027] In traditional systems the cryptographic keys used to encipher traffic intended for a secure network connection were accessible to host processor 210. In one embodiment crypto engine 232 provides the keys for enciphering traffic, and provides access to hardware encryption services. In this manner host processor 210 may not have access to the keys, even though host processor can request the encryption services through crypto engine 232. [0028] Client 200 also includes secure storage 240, which is accessible by platform chipset 230, but is independent of, and transparent to host processor 210. Secure storage 240 represents a combination of non- volatile storage (e.g., flash) with logic that prevents unauthorized access to the non- volatile storage. For example, secure storage 240 may be a trusted platform module (TPM). [0029] In one embodiment client 200 may include flash 250. Flash 250 represents a non¬ volatile storage upon which data related to the security of client 200 may be stored. For example, in one embodiment an image of the host is stored that can be verified to make sure the system has not been compromised. The determination of whether the system has been compromised is performed by an agent on platform chipset 230 that is part of, or works in conjunction with crypto engine 232. In this way crypto engine 232 may determine whether the system is compromised before providing access of a compromised system to network link 234. [0030] Figure 3 is one embodiment of a block diagram of a network endpoint device having cooperative embedded agents. The block diagram of Figure 3 is intended to represent a broad category of electronic systems having network interfaces. The electronic system can be, for example, a desktop computer system, a mobile computer system, a server, a personal digital assistant (PDA), a cellular telephone, a set-top box, game console, satellite receiver, etc. [0031] In one embodiment, processor 310 may be coupled to memory controller hub 320 by front side bus 315. While the electronic system of Figure 3 is described as having a single processor, multiple processor embodiments can also be supported. In an alternate embodiment, processor 310 may be coupled with memory controller hub 320 by a shared system bus. Processor 310 can be any type of processor known in the art, for example, a processor from the Pentium® family of processors, the Itanium® family of processors, the Xeon® family of processors, available from Intel Corporation of Santa Clara, California. Other processors can also be used. [0032] Memory controller hub 320 may provide an interface to memory subsystem 125 that can include any type of memory to be used with the electronic system. Memory controller hub 320 may also be coupled with input/output (I/O) controller hub (ICH) 330. In one embodiment, ICH 330 may provide an interface between the system and peripheral I/O devices 380 as well as between the system and network interface 340, which may provide an interface to external network 390. Digital signal processor (DSP) 331 may also be coupled with ICH 330. Network 390 may be any type of network, whether wired or wireless, for example, a local area network or a wide area network. [0033] In one embodiment, ICH 330 may be coupled with secure memory structure 370, which may provide security and/or cryptographic functionality. In one embodiment, secure memory structure 370 may be implemented as a trusted platform module (TPM). Secure memory structure 370 may provide a secure identifier, for example, a cryptographic key in a secure manner to embedded agent 351. [0034] Embedded agent 351 represents an embedded module or modules, whether in hardware or firmware, with a private network connection transparent to host processor 310. In one embodiment embedded agent 351 may be considered to have at least two separate parts, that may be physically or merely logically separate. Embedded agent 351 may physically be separate from ICH 330. In another embodiment, embedded agent 351 is physically integrated with ICH 330. [0035] Embedded controller agent 150 may be coupled with ICH 130 and with network 190. The network connection for embedded controller 150 may be independent of the operation of the system and is independent of an operating system executed by processor 110. In one embodiment, embedded controller agent 150 may include a microcontroller or other type of processing circuitry, memory and interface logic. Embodiments of embedded agent 351 are described in greater detail below. [0036] In one embodiment, embedded controller agent 350 may be coupled with processor 310 via an interrupt interface. For example, embedded controller agent 350 may be coupled with the SMI pin of a Pentium® processor or with the PMI pin of an Itanium® processor (generically, xMI line 355). Other system interrupt signals may be used for other processors. [0037] ICH 330 may also be coupled with embedded firmware agent 360. In one embodiment, embedded firmware agent 360 may be a mechanism that enables executable content in the form of one or more software drivers to be loaded into a management mode of processor 310. Embedded agent 351 may be executed in a combination of hardware and/or software. The software may be transmitted to the system of Figure 3 by means of a machine accessible medium, which includes any mechanism that provides (i.e., stores and/or transmits) information in a form accessible by a machine (e.g., a computer, network device, personal digital assistant, manufacturing tool, any device with a set of one or more processors, etc.). For example, a machine accessible medium includes recordable/non- recordable media (e.g., read only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices; etc.), and electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), etc. [0038] In one embodiment, embedded controller agent 350 may be coupled with embedded firmware agent 360 via agent bus 365. Agent bus 365 may be a bi-directional private bus between the elements of embedded agent 351. Because one or more aspects of embedded agent 351 may be firmware, agent bus 365 is to be understood as a logical, functional connection between embedded controller agent 350 and embedded firmware agent 360, and not necessarily a physical link. By communicating over agent bus 365, embedded controller agent 350 and embedded firmware agent 360 may be configured to provide manageability and/or security functionality to the system in a secure and convenient manner. [0039] In one embodiment, embedded controller agent 350 may provide an integrity check on the system for security purposes, for example, prior to establishing a secure or trusted connection with a remote device via network 390. Embedded controller agent may perform a virus scan of the system to determine whether communication with the remote device is safe and/or whether support is required from the remote device. Embedded firmware agent 360 may provide an operating system-independent, secure storage for use by embedded controller agent 350 in performing the integrity check. [0040] During operation, embedded controller agent 350 may perform periodic integrity checks to provide enhanced security as compared to a single integrity check. Embedded controller agent 350 can also perform integrity checks prior to communication with remote management devices. [0041] Figure 4 is one embodiment of a block diagram of elements of a network endpoint device. I/O controller hub (ICH) 410 represents I/O controller hardware on a computing device. ICH 410 may be a chip or chipset with the control logic and interfaces, together with any discrete components that may make up ICH 410. In one embodiment embedded agent 411 is integrated onto the hardware of ICH 410. IfICH 410 is a chipset, embedded agent 411 may be a chip in the chipset and/or firmware no a chip in the chipset. If ICH 410 is a single chip, embedded agent 411 may be a separate circuit integrated onto the ICH 410 chip, and may share I/O pins, or have dedicated I/O pins in the package, or be embedded firmware in a storage of the chip (e.g., read-only memory, flash) that is executed by the ICH 410 chip. [0042] In one embodiment embedded agent 411 includes an embedded firmware agent to participate in the distribution of cryptographic keys, and manage a shared key or keys. A shared key is a key that is shared among multiple clients as part of a virtual group. The ability of the clients in the virtual group to function as a virtual group and use a shared private key depends upon the distributed ability of each client to maintain the security of the shared key. [0043] To maintain the security of the shared key, embedded agent 411 has private network connectivity as represented by agent line 412. A private network connection refers to a connection that is not visible by and/or not accessible to a host operating system. To provide the best security, agent line 412 should be isolated from the central processor of the endpoint device. This is because the central processor may be subject to compromise from attack, and preventing the central processor direct access to agent line 412 will mean that even if an OS running on the central processor is compromised, the security of agent line 412 will likely not be compromised. [0044] To communicate on agent line 412, embedded agent 411 may utilize the shared cryptographic key. Thus, security of each client in the virtual group is ensured by the use of an embedded agent, such as embedded agent 411, that has a private network link inaccessible to the host processor over which the embedded agent may receive and distribute the shared key. The use of the shared key is thus transparent to the host processor, and will not be compromised by an attack on the host processor. [0045] Traditional systems have also been vulnerable in attacks because their cryptographic keys were stored in memory accessible to the OS or user applications. To ensure the security of the shared cryptographic key, embedded agent 411 interfaces with secure key storage (SKS) 421 located on the host platform. In one embodiment, SKS 421 is located on network interface 420. Network interface 420 represents a network card (e.g., network interface card (NIC)), or a network interface circuit integrated onto the hardware/firmware platform of the host computing device. Embedded agent 411 will receive a shared key to be used by each client in the virtual group to identify the client as a member of the virtual group. Embedded agent 411 passes the key to SKS 421 and causes the key to be stored. [0046] In another embodiment, SKS 421 resides on the platform hardware not on the network interface 420. For example, SKS 421 could be a separate chip on a main circuit board. In another example, SKS 421 could be integrated with embedded agent 411, such as by integrating the logic of embedded agent 411 and the memory and logic of SKS 421 on a single integrated circuit or system on a chip. [0047] The key exchange between SKS 421 and embedded agent 411, GCM 422, and/or other hardware in the system will typically be across a private bus, or a bus not generally accessible in a host system. Alternatively, the internal key exchange may take place with encryption across a more generally accessible system bus. [0048] In one embodiment network interface 420 also includes Galois counter mode encryption module (GCM) 422. In alternate embodiments other hardware encryption modules may be used. GCM 422 may be hardware embedded on the system, or software running on an embedded entity on the system. GCM 422 has secure access to SKS 421 as described above. GCM 422 may obtain the shared key from SKS 421 to perform cryptographic services on data intended for secure transmission on the network. [0049] Figure 5 is one embodiment of a flow diagram of accessing a traffic flow with a shared cryptographic key. A system that participates in a network with shared cryptographic key(s) will typically obtain and store a shared key for use in secure communication. A system according to embodiments of the invention described herein may have a key from boot-up of a host operating system running on the system. The system at some point requests to transmit over a secure communication link to an endpoint on the network, 502. The system includes hardware and/or firmware to provide secure access to and secure storage of a shared symmetric cryptographic key. This includes an embedded agent that maintains the cryptographic key(s). [0050] In one embodiment prior to a transmission in the virtual network, the embedded agent verifies security of the platform, 504. In alternate embodiments the security may be known beforehand from prior verification. In the shared key network, the security is dependent upon each client securing the shared key, and preventing the client computing device from transmitting over a secure link if the client is compromised. Thus, the embedded agent verifies the client platform, including the software running on client, to determine if the client has been compromised by e.g., a virus, worm, hacker attack, etc. [0051] In a system that uses a shared cryptographic key, the sharing of the key presents many advantages as far as management, and integration of the system with other network hardware. However, security of the shared key becomes significantly important. A compromise of a client that results in dissemination of the shared key would destroy trust in the security of all secure communication in the network among clients sharing the key. Thus, in one embodiment the integrity of the system platform is constantly monitored to verify that it is secure. Even if the platform is determined to be free from compromise and the system continues to perform other operations, monitoring of the system integrity may be continued in parallel with the other operations. Note that in parallel does not necessarily infer that a single system element is performing both the monitoring and the other operations. There may be different hardware, software, and/or firmware elements independently and/or concurrently performing the system operations and the monitoring functions. [0052] If the embedded agent determines that the platform has been compromised, 510, the embedded agent may perform security protection operations, 512. Security protection may include, but is not limited to, transmitting on the secure link to a network manager that the client has been compromised, causing execution of security software, causing the client to reboot, preventing the client from transmitting to the network on its network access ports, etc. These operations may be performed in combination as well as individually, or in a sequence. [0053] If the embedded agent determines that the platform has not been compromised, 510, the cryptographic services module (e.g., hardware, software) is provided access to obtain the shared key from a secure storage to perform encryption/decryption of data, 514. The cryptographic services are the provided with the shared key, 516. In the case of hardware encryption, a hardware module may obtain the key directly through a bus to the secured memory storing the shared key. The key is then used to perform the cryptographic services. In the case of software encryption, the software may make a call (e.g., application program interface (API)) to the embedded agent, which provides access to cryptographic services for the software. For example, access to services may be provided through interchange in a read/write area of system memory, and the shared key is not disclosed to the requesting OS or application(s). [0054] To communicate over the virtual network of which the client is a part, the client will provide authentication to identify itself to a verification module on the network, 518. For example, a client may provide authentication to a firewall that isolates the virtual network from the outside. In one embodiment the embedded agent provides authentication with a shared key to the verification module over the secure line the embedded agent has to the network. When authenticated, the client may be allowed to transmit, 520. [0055] Figure 6 is one embodiment of a block diagram of use of an infrastructure device with endpoints having embedded agents for sharing a cryptographic key. Endpoints 610- 611 desire to engage in secure communication, and will use enciphering/deciphering of data transmitted over a network connecting them. Endpoints 610-611 include embedded agents 620-621, respectively, and secure memory, illustrated as trusted platform modules (TPMs) 630-631, respectively. The operation of embedded agents 620-621 and TPMs 630-631 is according to embodiments of these devices as discussed above. [0056] Endpoints 610-611 are shown interacting through infrastructure device 640. Infrastructure device may be, for example, a firewall, switching device with restricted access services, etc. Infrastructure device 640 provides security by allowing authenticated traffic 650 to pass through infrastructure device 640, and rejecting unauthenticated traffic 660. Authenticated traffic 650 is transmitted through "holes" 641 in infrastructure device 640 opened to authenticated traffic 650. [0057] To determine whether network data should be trusted (650) or untrusted (660), infrastructure device 640 includes verification engine 642. Verification engine 642 communicates through links 670-671 with embedded agents 620-621 of endpoints 610- 611, respectively. In one embodiment the verification information is in the fact that authenticated data 651 was hashed or cryptographically altered using the shared key. Also, the verification information may be in the fact that authenticated data 651 includes a header with the shared key or a derivative of the shared key. [0058] Endpoints 610-611 use shared symmetric cryptographic keys for engaging in secure communication. The shared keys are common to endpoints that are part of a virtual network of devices. Embedded agents 620-621 verify the identity of endpoints 610-611, respectively, as belonging to the virtual network by the use of the shared key. When the identity and security of endpoints 610-611 is verified, they may engage in communication. For example, endpoint 611 may transmit authenticated data 651 to endpoint 610. [0059] The infrastructure devices of a network may thus be easily used with groups that share private cryptographic keys. Note that links 670-671, while shown as separate from authenticated data 650 are not necessarily to be understood as referring to separate physical links from endpoints 610-611 to infrastructure device 640. Link 670, which is accessible only to embedded agent 620, may be a private communication channel over the same physical link that carries data on other channels accessible from elements of endpoint 610 that may be subject to compromise. While made in reference to endpoint 610 and secure link 670, the same description applies to endpoint 611 and its associated secure link 671. [0060] Reference herein to "embodiment" means that a particular feature, structure or characteristic described in connection with the described embodiment is included in at least one embodiment of the invention. Thus, the appearance of phrases such as "in one embodiment," or "in alternate an embodiment" may describe various embodiments of the invention, and may not necessarily all refer to the same embodiment. Besides what is described herein, it will be appreciated that various modifications may be made to embodiments of the invention without departing from their scope. Therefore, the illustrations and examples herein should be construed in an illustrative, and not a restrictive sense. The scope of the invention should be measured solely by reference to the claims that follow.