Abstract:
Multiple trusted platform modules within a data processing system are used in a redundant manner that provides a reliable mechanism for securely storing secret data at rest that is used to bootstrap a system trusted platform module. A hypervisor requests each trusted platform module to encrypt a copy of the secret data, thereby generating multiple versions of encrypted secret data values, which are then stored within a non-volatile memory within the trusted platform. At some later point in time, the encrypted secret data values are retrieved, decrypted by the trusted platform module that performed the previous encryption, and then compared to each other. If any of the decrypted values do not match a quorum of values from the comparison operation, then a corresponding trusted platform module for a non-matching decrypted value is designated as defective because it has not been able to correctly decrypt a value that it previously encrypted.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an improved data processing system and, in particular, to a method and apparatus for data storage protection using cryptography. 
     2. Description of Related Art 
     Most data processing systems contain sensitive data and sensitive operations that need to be protected. For example, the integrity of configuration information needs to be protected from illegitimate modification, while other information, such as a password file, needs to be protected from illegitimate disclosure. As another example, a data processing system needs to be able to reliably identify itself to other data processing systems. 
     An operator of a given data processing system may employ many different types of security mechanisms to protect the data processing system. For example, the operating system on the data processing system may provide various software mechanisms to protect sensitive data, such as various authentication and authorization schemes, while certain hardware devices and software applications may rely upon hardware mechanisms to protect sensitive data, such as hardware security tokens and biometric sensor devices. 
     The integrity of a data processing system&#39;s data and its operations, however, centers around the issue of trust. A data processing system&#39;s data and operations can be verified or accepted by another entity if that entity has some manner for establishing trust with the data processing system with respect to particular data items or particular operations. 
     Hence, the ability to protect a data processing system is limited by the manner in which trust is created or rooted within the data processing system. To address the issues of protecting data processing systems, a consortium of companies has formed the Trusted Computing Group (TCG) to develop and to promulgate open standards and specifications for trusted computing. According to the specifications of the Trusted Computing Group, trust within a given data processing system or trust between a data processing system and another entity is based on the existence of a hardware component within the data processing system that has been termed the trusted platform module (TPM). 
     A trusted platform module physically secures and protects certain cryptographic key data. Each trusted platform module is unique at the point of manufacture. If a trusted platform module fails, the cryptographic key material that is protected by the device is rendered unusable. 
     Current trusted platform architectures focus on low-cost security modules, which are tied to a single system, such as a desktop computer or portable computer. Although these low-cost security modules are not necessarily prone to failure, the failure of a security module within a desktop computer would generally have less costly and less labor-intensive consequences than the failure of a similar security module within a high-performance server, which are often manufactured with redundant capabilities in order to avoid an unacceptable single point of failure. 
     Therefore, it would be advantageous to have a mechanism for improving the availability of a trusted platform module. It would be particularly advantageous to allow the use of low-cost trusted platform modules while ensuring system availability. 
     SUMMARY OF THE INVENTION 
     A method, a system, an apparatus, and a computer program product enable multiple trusted platform modules to be used in a redundant manner within a data processing system. A hypervisor that is executing on the data processing system reads secret data stored within a trusted platform in the data processing system and then requests that each trusted platform module in the data processing system encrypt a copy of the secret data, thereby generating multiple versions of encrypted secret data values. The encrypted secret data values are stored within a non-volatile memory within the trusted platform. At some later point in time, the encrypted secret data values are retrieved, decrypted by the trusted platform module that performed the previous encryption, and then compared to each other. If any of the decrypted values do not match a quorum of values from the comparison operation, then a corresponding trusted platform module for a non-matching decrypted value is designated as defective because it has not been able to correctly decrypt a value that it previously encrypted. Establishing a quorum of multiple trusted platform modules provides a reliability mechanism for securely storing secret material at rest that is used to bootstrap the system trusted platform module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, further objectives, and advantages thereof, will be best understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1A  depicts a typical network of data processing systems, each of which may implement the present invention; 
         FIG. 1B  depicts a typical computer architecture that may be used within a data processing system in which the present invention may be implemented; 
         FIG. 2  depicts a block diagram that shows an example of a typical trusted platform architecture; 
         FIG. 3  depicts a block diagram that shows some of the major components of a typical trusted platform module; 
         FIG. 4  depicts a block diagram that shows some of the components on a trusted platform that contains redundant trusted platform modules in accordance with an embodiment of the present invention; 
         FIG. 5  depicts a flowchart that shows a configuration process for a system that employs multiple redundant physical trusted platform modules in accordance with an embodiment of the present invention; 
         FIG. 6  depicts a flowchart that shows a bootstrapping process for a data processing system that employs multiple redundant physical trusted platform modules in accordance with an embodiment of the present invention; and 
         FIG. 7  depicts a flowchart that shows a process for incorporating a new trusted platform module within a data processing system that employs multiple redundant physical trusted platform modules in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In general, the devices that may comprise or relate to the present invention include a wide variety of data processing technology. Therefore, as background, a typical organization of hardware and software components within a distributed data processing system is described prior to describing the present invention in more detail. 
     With reference now to the figures,  FIG. 1A  depicts a typical network of data processing systems, each of which may implement a portion of the present invention. Distributed data processing system  100  contains network  101 , which is a medium that may be used to provide communications links between various devices and computers connected together within distributed data processing system  100 . Network  101  may include permanent connections, such as wire or fiber optic cables, or temporary connections made through telephone or wireless communications. In the depicted example, server  102  and server  103  are connected to network  101  along with storage unit  104 . In addition, clients  105 - 107  also are connected to network  101 . Clients  105 - 107  and servers  102 - 103  may be represented by a variety of computing devices, such as mainframes, personal computers, personal digital assistants (PDAs), etc. Distributed data processing system  100  may include additional servers, clients, routers, other devices, and peer-to-peer architectures that are not shown. 
     In the depicted example, distributed data processing system  100  may include the Internet with network  101  representing a worldwide collection of networks and gateways that use various protocols to communicate with one another, such as Lightweight Directory Access Protocol (LDAP), Transport Control Protocol/Internet Protocol (TCP/IP), Hypertext Transport Protocol (HTTP), Wireless Application Protocol (WAP), etc. Of course, distributed data processing system  100  may also include a number of different types of networks, such as, for example, an intranet, a local area network (LAN), or a wide area network (WAN). For example, server  102  directly supports client  109  and network  110 , which incorporates wireless communication links. Network-enabled phone  111  connects to network  110  through wireless link  112 , and PDA  113  connects to network  110  through wireless link  114 . Phone  111  and PDA  113  can also directly transfer data between themselves across wireless link  115  using an appropriate technology, such as Bluetooth™ wireless technology, to create so-called personal area networks (PAN) or personal ad-hoc networks. In a similar manner, PDA  113  can transfer data to PDA  107  via wireless communication link  116 . 
     The present invention could be implemented on a variety of hardware platforms;  FIG. 1A  is intended as an example of a heterogeneous computing environment and not as an architectural limitation for the present invention. 
     With reference now to  FIG. 1B , a diagram depicts a typical computer architecture of a data processing system, such as those shown in  FIG. 1A , in which the present invention may be implemented. Data processing system  120  contains one or more central processing units (CPUs)  122  connected to internal system bus  123 , which interconnects random access memory (RAM)  124 , read-only memory  126 , and input/output adapter  128 , which supports various I/O devices, such as printer  130 , disk units  132 , or other devices not shown, such as an audio output system, etc. System bus  123  also connects communication adapter  134  that provides access to communication link  136 . User interface adapter  148  connects various user devices, such as keyboard  140  and mouse  142 , or other devices not shown, such as a touch screen, stylus, microphone, etc. Display adapter  144  connects system bus  123  to display device  146 . 
     Those of ordinary skill in the art will appreciate that the hardware in  FIG. 1B  may vary depending on the system implementation. For example, the system may have one or more processors, such as an Intel® Pentium®-based processor and a digital signal processor (DSP), and one or more types of volatile and non-volatile memory. Other peripheral devices may be used in addition to or in place of the hardware depicted in  FIG. 1B . The depicted examples are not meant to imply architectural limitations with respect to the present invention. 
     In addition to being able to be implemented on a variety of hardware platforms, the present invention may be implemented in a variety of software environments. A typical operating system may be used to control program execution within each data processing system. For example, one device may run a Unix® operating system, while another device contains a simple Java® runtime environment. A representative computer platform may include a browser, which is a well known software application for accessing hypertext documents in a variety of formats, such as graphic files, word processing files, Extensible Markup Language (XML), Hypertext Markup Language (HTML), Handheld Device Markup Language (HDML), Wireless Markup Language (WML), and various other formats and types of files. 
     The present invention may be implemented on a variety of hardware and software platforms, as described above with respect to  FIG. 1A  and  FIG. 1B . More specifically, though, the present invention is directed to enabling trusted computing platforms. Before describing the present invention in more detail, though, some background information about trusted computing platforms is provided for evaluating the operational efficiencies and other advantages of the present invention. Although the present invention may be implemented in conjunction with a variety of trusted computing platforms, possibly in accordance with one or more standards, the examples of the present invention hereinbelow employ the terminology and examples from the standards and/or specifications that have been promulgated by the Trusted Computing Group (TCG); it should be noted, though, that the examples are not meant to imply architectural, functional, nor definitional limitations with respect to embodiments of the present invention. 
     With reference now to  FIG. 2 , a block diagram depicts some of the components in a data processing system that is constructed using a model of a trusted platform architecture. Trusted platform architectures may be implemented for particular computational environments or for particular classes of devices;  FIG. 2  depicts a trusted platform architecture in accordance with the TCG&#39;s PC-specific implementation specification. 
     System  200  supports execution of software components, such as operating system  202 , applications  204 , and drivers  206 , on its platform  208 . The software components may be received through a network, such as network  101  that is shown in  FIG. 1A , or they may be stored, e.g., on hard disk  210 . Platform  208  receives electrical power from power supply  212  for executing the software components on add-on cards  214  and motherboard  216 , which includes typical components for executing software, such as CPU  218  and memory  220 , although motherboard  216  may include multiple CPU&#39;s. Interfaces  222  connect motherboard  216  to other hardware components within system  200 , and firmware  224  contains POST BIOS (power-on self-test basic input/output system)  226 . 
     Motherboard  216  also comprises trusted building block (TBB)  228 ; motherboard  216  is supplied by a manufacturer with TBB  228  and other components physically or logically attached and supplied by the manufacturer. TBB  228  comprises the combination of the core root of trust for measurement (CRTM) component  230 , the trusted platform module (TPM)  232 , the connection of the CRTM to motherboard  216 , and the connection of the TPM to motherboard  216 . 
     TPM  232  is explained in more detail with respect to  FIG. 3  hereinbelow. CRTM  230  is an immutable portion of the platform&#39;s initialization code that executes upon a platform reset; the platform&#39;s execution must begin at the CRTM upon any platform reset event. In this manner, the trust in the platform is based on the CRTM and the behavior of the TPM, and the trust in all measurements is based on the integrity of the CRTM. In the example that is shown in  FIG. 2 , the BIOS may be assumed to include a BIOS Boot Block and POST BIOS  226 ; each of these are independent components that can be updated independent of each other, wherein the manufacturer must control the update, modification, and maintenance of the BIOS Boot Block, but a third party supplier may update, modify, or maintain the POST BIOS component. In the example that is shown in  FIG. 2 , the CRTM may be assumed to be the BIOS Boot Block, and the POST BIOS is a measured component of the chain of trust. Alternatively, the CRTM may comprise the entire BIOS. 
     With reference now to  FIG. 3 , a block diagram depicts some of the major components of a trusted platform module according to TCG specifications. Trusted platform module  300  comprises input/output component  302 , which manages information flow over communications bus  304  by performing appropriate protocol encoding/decoding operations and routing of messages to appropriate components. Cryptographic co-processor  306  performs cryptographic operations within a trusted platform module. Key generator  308  creates symmetric keys and RSA asymmetric cryptographic key pairs. HMAC engine  310  performs HMAC (Keyed-Hashing for Message Authentication) calculations, whereby message authentication codes are computed using secret keys as integrity checks to validate information transmitted between two parties, e.g., in accordance with Krawczyk et al., “HMAC: Keyed-Hashing for Message Authentication”, Request for Comments (RFC) 2104, Internet Engineering Task Force (IETF), February 1997. 
     Random number generator  312  acts as a source of randomness for the computation of various values, such as nonces, keys, or other values. SHA-1 engine  314  implements the SHA-1 hash algorithm. Power detector  316  manages the power states of a trusted platform module in association with the power states of the platform. Opt-in component  318  maintains the state of persistent and volatile flags and enforces semantics associated with those flags such that the trusted platform module may be enabled and disabled. Execution engine  320  runs program code to execute commands that the trust platform module receives through input/output component  302 . Non-volatile memory  322  stores persistent identity and state associated with the trusted platform module; the non-volatile memory may store static data items but is also available for storing dynamic data items by entities that are authorized by the trusted platform module owner, whereas volatile memory  324  stores dynamic data items. 
     Given the background information on trusted computing platforms that has been described with respect to  FIG. 2  and  FIG. 3 , a detailed description of the present invention is provided hereinbelow with respect to the remaining figures. As noted above, typical trusted platforms have been designed such that a trusted platform module exists within a trusted platform architecture as a potentially catastrophic single point of failure, which would be unacceptable behavior in a high-performance server or similar high-cost computing device. The present invention addresses this problem by providing redundancy with trusted platform modules as explained in more detail hereinbelow. 
     With reference now to  FIG. 4 , a block diagram depicts some of the components on a trusted platform that contains redundant trusted platform modules in accordance with an embodiment of the present invention. Hypervisor runtime  400  contains system TPM functional unit  402  within which secret data  404  either has been injected by the manufacturer during the manufacture of system TPM functional unit  402  or has been generated by system TPM functional unit  402 . Non-volatile RAM  406  provides a secure datastore; access to non-volatile RAM  406  is physically hardware-restricted to hypervisor  400 , which uses non-volatile RAM  406  to store different encrypted versions of secret data  404 . Hypervisor  400  invokes functionality in TPM  408 , TPM  410 , and TPM  412  to generate encrypted secret data  414 , encrypted secret data  416 , and encrypted secret data  418 , respectively. Multiple TPM&#39;s are available in a redundant manner; the trusted platform comprises a minimum of three trusted platform modules for completing a redundancy operation through the use of TPM integrity comparison unit  420  in hypervisor  400 , as explained in more detail further below. 
     With reference now to  FIG. 5 , a flowchart depicts a configuration process for a data processing system that employs multiple redundant physical trusted platform modules in accordance with an embodiment of the present invention. The process commences with a hypervisor on a trusted platform of a data processing system detecting that encrypted secret data that will be used when bootstrapping the data processing system has not yet been generated; for example, the hypervisor determines that the non-volatile RAM (NVRAM) on the trusted platform does not yet store the encrypted secret data (step  502 ). Preferably, predetermined locations within the non-volatile RAM are reserved for the encrypted secret data, and the hypervisor may check those particular locations for valid data. It may be assumed that the secret data either has been injected by the manufacturer during the manufacture of the trusted platform or has been generated by the trusted platform during the manufacturing process or at some other time, such as the process of taking ownership of the trusted platform. The process that is shown in  FIG. 5  may occur during the manufacture of the trusted platform, or it may occur when an entity takes ownership of the trusted platform. 
     After determining that the non-volatile RAM does not yet hold the encrypted secret data, the hypervisor requests each trusted platform module on the trusted platform to encrypt the secret data. The hypervisor obtains a copy of the secret data (step  504 ) and determines if there is a TPM that has not yet been used to generate an encrypted version of the secret data (step  506 ); if not, then the process is concluded. If all of the TPM&#39;s have not yet already generated an encrypted version of the secret data, then the hypervisor sends a request to the next unused TPM to encrypt a copy of the secret data (step  508 ), which is then stored into the non-volatile RAM (step  510 ). The hypervisor calls on each TPM, thereby generating multiple encrypted versions of the secret data through the redundant TPM&#39;s until the process is concluded. By performing this process during the manufacture or configuration of the trusted platform, the process that is shown in  FIG. 5  creates a set of checkpoint values that may be subsequently used to determine whether or not a trusted platform module has become defective. 
     With reference now to  FIG. 6 , a flowchart depicts a portion of a bootstrapping process for a data processing system that employs multiple redundant physical trusted platform modules in accordance with an embodiment of the present invention. The process commences with the starting of the hypervisor on a trusted platform of a data processing system, e.g., during startup or restart of the data processing system, after which the hypervisor reads the multiple encrypted versions of the secret data that were previously stored within the non-volatile RAM on the trusted platform (step  602 ), e.g., using the process that is depicted within  FIG. 5 . The hypervisor decrypts each encrypted version of the secret data using the respective TPM that generated the encrypted version (step  604 ). 
     The hypervisor then compares the decrypted values against each other to determine whether or not all of the decrypted values are equal to each other (step  606 ). If the decrypted values are all equal to each other, then the hypervisor may continue its bootstrapping process (step  608 ), and the process is concluded. If it is determined that no decrypted values are equal to any other decrypted values (step  610 ), then the boot process is stopped (step  612 ) or, alternatively, the boot process continues but without TPM functionality on the data processing system. 
     The process then continues by attempting to determine if a quorum has been established among the decrypted values. In other words, the decrypted values are compared, and equal values are logically grouped to determine if a set of equal values represents a majority of the set of available values, i.e., greater than fifty percent of the available values. If so, then a quorum has been established. If there is a set of equal values but it does not represent a majority of the set of available values, then a quorum has not been established. In alternative embodiments, other comparative algorithms may be employed, possibly depending on the number of TPM&#39;s within the data processing system. 
     Hence, if it is determined that there is a quorum amongst the decrypted values, then an error flag is set for each TPM that failed to generate a matching value with the majority of TPM&#39;s (step  614 ), and the booting process is allowed to continue (step  616 ); in other words, each TPM that failed to produce a value in the quorum is flagged as being in error. Alternatively, other methods for designating a TPM as defective may be used. 
     For example, referring again to  FIG. 4 , an example of a trusted platform depicts a minimum of three TPM&#39;s. Using the process that is shown in  FIG. 6  for a system with three TPM&#39;s, if two TPM&#39;s are able to generate two matching decrypted values for the previously encrypted secret data, then the bootstrapping process is able to continue; in other words, a quorum is determined to exist with at least two matching decrypted values. 
     With reference now to  FIG. 7 , a flowchart depicts a process for incorporating a new trusted platform module within a data processing system that employs multiple redundant physical trusted platform modules in accordance with an embodiment of the present invention. The process that is shown in  FIG. 7  assumes that a failed TPM has previously been detected and flagged, e.g., using the process that is depicted within  FIG. 6 , possibly followed by logging the event for a system administrator to discover and review. The failed TPM would then be physically removed and replaced with a new TPM. 
     The process commences at some later point in time when the hypervisor detects the new TPM (step  702 ). If necessary, the hypervisor clears the proper location within the non-volatile RAM on the trusted platform that has been reserved for holding corresponding data from the replaced TPM (step  704 ). The hypervisor obtains a copy of the secret data (step  706 ) and sends a request to the new TPM to encrypt a copy of the secret data (step  708 ), which is then stored into a predetermined location within the non-volatile RAM (step  710 ) so that the non-volatile RAM contains all of the data that would be necessary for completing a TPM integrity check operation when bootstrapping the data processing system in the manner that is described above with respect to  FIG. 6 . 
     The advantages of the present invention should be apparent in view of the detailed description that is provided above. By maintaining multiple copies of the encrypted secret data in non-volatile RAM, each of which corresponds to a trusted platform module within the data processing system, the hypervisor within the data processing system is able to detect the failure of one or more TPM&#39;s by decrypting the copies of the encrypted secret data and comparing the decrypted values in an attempt to establish a quorum among the decrypted values. If a quorum is found among the decrypted values, the data processing system may continue to operate without suffering catastrophic failure of the entire data processing system that might have otherwise been caused by the failed TPM(s) on a typical prior art system. 
     It is important to note that while the present invention has been described in the context of a fully functioning data processing system, those of ordinary skill in the art will appreciate that the processes of the present invention are capable of being distributed in the form of instructions in a computer readable medium and a variety of other forms, regardless of the particular type of signal bearing media actually used to carry out the distribution. Examples of computer readable media include media such as EPROM, ROM, tape, paper, floppy disc, hard disk drive, RAM, and CD-ROMs. Examples of transmission-type media include media such as digital and analog communications links. 
     A method is generally conceived to be a self-consistent sequence of steps leading to a desired result. These steps require physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It is convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, parameters, items, elements, objects, symbols, characters, terms, numbers, or the like. It should be noted, however, that all of these terms and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. 
     The description of the present invention has been presented for purposes of illustration but is not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments were chosen to explain the principles of the invention and its practical applications and to enable others of ordinary skill in the art to understand the invention in order to implement various embodiments with various modifications as might be suited to other contemplated uses.