Abstract:
A system and method for capturing non-forgeable packet traces. Upon start-up of a sniffer, a first quote of Platform Configuration Register (PCR) values in a Trusted Platform Module (TPM) utilized by the sniffer is obtained, wherein the first quote comprises a list of starting values in the PCRs and is signed by the TPM and stored in a packet log. When a packet of interest is intercepted by the sniffer, the sniffer obtains a hash of the packet and instructs the TPM to extend a PCR with the hash value. The packet of interest is then stored in the packet log. When the sniffer is shutdown, a second quote of values in the PCRs is obtained, wherein the second quote comprises a list of current values in the PCRs, and wherein the second quote is signed by the TPM and stored in the packet log.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to wiretapping electronic communications, and in particular to a computer implemented method, data processing system, and computer program product for authenticating or “notarizing” packet traces. 
         [0003]    2. Description of the Related Art 
         [0004]    Wiretapping is the process of monitoring telephone or electronic communications by third party, often by covert means. This process of intercepting telephone conversations and electronic communications such as faxes, email, and other data transfers provides an effective investigation tool to be used by law enforcement agencies. To implement a wiretap, law enforcement agencies typically issue a wiretap request to the central office of the telephone companies or Internet Service Providers (ISPs). Examples of wiretapping products employed by law enforcement agencies to intercept electronic communications include Carnivore, which was developed by the U.S. Federal Bureau of Investigation, and Cyveillance, a commercial product. The Carnivore system is deployed at the ISP of the person for whom the law enforcement officials have wiretap authorization to snoop and store their communication traces. Both Cyveillance and Carnivore operate essentially as packet sniffers, which are programs that can “see” all of the information passing over a network to which it is connected. The program looks at, or “sniffs”, each packet as the data streams over the network. The wiretap devices look for packets or communication sessions with particular packet attributes and if found, save the sessions to disk or tape for later viewing and use in court proceedings. However, if the chain of custody of generated computer records such as these stored sessions cannot be proven, a court may consider such records as hearsay, and special arguments must be made to be able to introduce the records as evidence in court. 
         [0005]    Existing methods in the current art for storing information related to a wiretap include hashing audit log records, using a hardware device to store the message digests of audit log records, integrating message digests into particular applications such as chat clients, and using a hardware device to store the message digests of a chat log. However, all of these existing methods typically store the wiretap information within a log and then perform a hash of the entire log. A hash function substitutes or transposes the data to create a digital “fingerprint”, or a hash value. A typical hash function comprises a short string of letters and numbers (binary data written in hexadecimal notation). When another hash value of the log is taken at a later time, the two hash values are compared. If the hash values match, the log is determined to be authentic. However, there may still be some question as to the authenticity of the data in a court of law since the computer data may potentially be altered prior to the initial hash of the complete log. There is currently no way to ensure that the data has not been altered or touched by someone in some way since the time it was collected. 
       SUMMARY OF THE INVENTION 
       [0006]    The illustrative embodiments provide a computer implemented method, data processing system, and computer program product for authenticating or “notarizing” packet traces. In particular, the illustrative embodiments provide a network sniffer for capturing non-forgeable packet traces. Responsive to a start-up of the sniffer, a first quote of values is obtained from one or more platform configuration registers in a trusted platform module utilized by the sniffer, wherein the first quote comprises a list of starting values in the platform configuration registers, and wherein the first quote is signed by the trusted platform module and stored in a packet log. When a packet of interest is intercepted at the sniffer, the sniffer obtains a hash of the packet of interest. The sniffer then instructs the trusted platform module to extend a platform configuration register with the hash of the packet of interest by appending the hash of the packet of interest to the hash of the current value of the platform configuration register and hashing this value to create the new hash which is stored in the PCR. The sniffer may instruct the trusted platform module to extend the platform configuration register by calling a PCRExtend API. The packet of interest is then stored in the packet log. When the sniffer is shutdown, a second quote of values in the platform configuration registers is obtained, wherein the second quote comprises a list of current values in the platform configuration registers, and wherein the second quote is signed by the trusted platform module and stored in the packet log. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
           [0008]      FIG. 1  depicts a pictorial representation of a distributed data processing system in which the illustrative embodiments may be implemented; 
           [0009]      FIG. 2  is a block diagram of a data processing system in which the illustrative embodiments may be implemented; 
           [0010]      FIG. 3  is a block diagram of an exemplary trusted platform architecture in which the illustrative embodiments may be implemented; 
           [0011]      FIG. 4  is a block diagram illustrating an exemplary trusted platform architecture with which the illustrative embodiments may be implemented; 
           [0012]      FIGS. 5A and 5B  are block diagrams of known wiretapping configurations; 
           [0013]      FIG. 6  is a block diagram of an exemplary wiretapping configuration comprising a secure non-repudiable sniffer in accordance with the illustrative embodiments; 
           [0014]      FIGS. 7A and 7B  depict an example log file in accordance with the illustrative embodiments; 
           [0015]      FIG. 8  is a flowchart illustrating the sniffer logic in accordance with the illustrative embodiments; and 
           [0016]      FIG. 9  is a flowchart illustrating the process of validating the proof of log correctness in accordance with the illustrative embodiments. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    With reference now to the figures and in particular with reference to  FIGS. 1-2 , exemplary diagrams of data processing environments are provided in which illustrative embodiments may be implemented. It should be appreciated that  FIGS. 1-2  are only exemplary and are not intended to assert or imply any limitation with regard to the environments in which different embodiments may be implemented. Many modifications to the depicted environments may be made. 
         [0018]    With reference now to the figures,  FIG. 1  depicts a pictorial representation of a network of data processing systems in which illustrative embodiments may be implemented. Network data processing system  100  is a network of computers in which embodiments may be implemented. Network data processing system  100  contains network  102 , which is the medium used to provide communications links between various devices and computers connected together within network data processing system  100 . Network  102  may include connections, such as wire, wireless communication links, or fiber optic cables. 
         [0019]    In the depicted example, server  104  and server  106  connect to network  102  along with storage unit  108 . In addition, clients  110 ,  112 , and  114  connect to network  102 . These clients  110 ,  112 , and  114  may be, for example, personal computers or network computers. In the depicted example, server  104  provides data, such as boot files, operating system images, and applications to clients  110 ,  112 , and  114 . Clients  110 ,  112 , and  114  are clients to server  104  in this example. Network data processing system  100  may include additional servers, clients, and other devices not shown. 
         [0020]    In the depicted example, network data processing system  100  is the Internet with network  102  representing a worldwide collection of networks and gateways that use the Transmission Control Protocol/Internet Protocol (TCP/IP) suite of protocols to communicate with one another. At the heart of the Internet is a backbone of high-speed data communication lines between major nodes or host computers, consisting of thousands of commercial, governmental, educational and other computer systems that route data and messages. Of course, network data processing system  100  also may be implemented as a number of different types of networks, such as for example, an intranet, a local area network (LAN), or a wide area network (WAN).  FIG. 1  is intended as an example, and not as an architectural limitation for different embodiments. 
         [0021]    With reference now to  FIG. 2 , a block diagram of a data processing system is shown in which illustrative embodiments may be implemented. Data processing system  200  is an example of a computer, such as server  104  or client  110  in  FIG. 1 , in which computer usable code or instructions implementing the processes may be located for the illustrative embodiments. 
         [0022]    In the depicted example, data processing system  200  employs a hub architecture including a north bridge and memory controller hub (MCH)  202  and a south bridge and input/output (I/O) controller hub (ICH)  204 . Processing unit  206 , main memory  208 , and graphics processor  210  are coupled to north bridge and memory controller hub  202 . Processing unit  206  may contain one or more processors and even may be implemented using one or more heterogeneous processor systems. Graphics processor  210  may be coupled to the MCH through an accelerated graphics port (AGP), for example. 
         [0023]    In the depicted example, local area network (LAN) adapter  212  is coupled to south bridge and I/O controller hub  204  and audio adapter  216 , keyboard and mouse adapter  220 , modem  222 , read only memory (ROM)  224 , universal serial bus (USB) ports and other communications ports  232 , and PCI/PCIe devices  234  are coupled to south bridge and I/O controller hub  204  through bus  238 , and hard disk drive (HDD)  226  and CD-ROM drive  230  are coupled to south bridge and I/O controller hub  204  through bus  240 . PCI/PCIe devices may include, for example, Ethernet adapters, add-in cards, and PC cards for notebook computers. PCI uses a card bus controller, while PCIe does not. ROM  224  may be, for example, a flash binary input/output system (BIOS). Hard disk drive  226  and CD-ROM drive  230  may use, for example, an integrated drive electronics (IDE) or serial advanced technology attachment (SATA) interface. A super I/O (SIO) device  236  may be coupled to south bridge and I/O controller hub  204 . 
         [0024]    An operating system runs on processing unit  206  and coordinates and provides control of various components within data processing system  200  in  FIG. 2 . The operating system may be a commercially available operating system such as Microsoft® Windows® XP (Microsoft and Windows are trademarks of Microsoft Corporation in the United States, other countries, or both). An object oriented programming system, such as the Java™ programming system, may run in conjunction with the operating system and provides calls to the operating system from Java programs or applications executing on data processing system  200 . Java and all Java-based trademarks are trademarks of Sun Microsystems, Inc. in the United States, other countries, or both. 
         [0025]    Instructions for the operating system, the object-oriented programming system, and applications or programs are located on storage devices, such as hard disk drive  226 , and may be loaded into main memory  208  for execution by processing unit  206 . The processes of the illustrative embodiments may be performed by processing unit  206  using computer implemented instructions, which may be located in a memory such as, for example, main memory  208 , read only memory  224 , or in one or more peripheral devices. 
         [0026]    The hardware in  FIGS. 1-2  may vary depending on the implementation. Other internal hardware or peripheral devices, such as flash memory, equivalent non-volatile memory, or optical disk drives and the like, may be used in addition to or in place of the hardware depicted in  FIGS. 1-2 . Also, the processes of the illustrative embodiments may be applied to a multiprocessor data processing system. 
         [0027]    In some illustrative examples, data processing system  200  may be a personal digital assistant (PDA), which is generally configured with flash memory to provide non-volatile memory for storing operating system files and/or user-generated data. A bus system may be comprised of one or more buses, such as a system bus, an I/O bus and a PCI bus. Of course the bus system may be implemented using any type of communications fabric or architecture that provides for a transfer of data between different components or devices attached to the fabric or architecture. A communications unit may include one or more devices used to transmit and receive data, such as a modem or a network adapter. A memory may be, for example, main memory  208  or a cache such as found in north bridge and memory controller hub  202 . A processing unit may include one or more processors or CPUs. The depicted examples in  FIGS. 1-2  and above-described examples are not meant to imply architectural limitations. For example, data processing system  200  also may be a tablet computer, laptop computer, or telephone device in addition to taking the form of a PDA. 
         [0028]    In situations where computer records are routinely and automatically generated, the current standard required for showing chain-of-custody for computer records in a court of law is for a forensics collector to generate hash values for the computer records and show that the records shown in court have the same hash value as the collected records. However, the reliability and believability of current chain-of-custody evidence is based on the credibility of the forensics collector, since the records and the hashes may be tampered with by anyone who touches the records both during collection and after collection but before they are presented in court. Thus, the hashes may be validated only by assertion that everyone in the chain of custody acted honorably. 
         [0029]    The illustrative embodiments address the problems in the current art by providing a computer implemented method, data processing system, and computer program product for authenticating or “notarizing” wiretaps of electronic communications. In particular, the illustrative embodiments enable network sniffers to apply a validation to computer records at the point of record collection, thereby allowing one to verify the authenticity of the packet traces for court proceedings. A sniffer is a program which monitors and captures data being transmitted on a network. With the illustrative embodiments, the reliability of the records may be increased by utilizing a hardware device, such as a Trusted Platform Module (TPM), in conjunction with a network sniffer to provide the capability of “notarizing” wiretaps. The hashing of the computer records in the illustrative embodiments is performed at record collection time, thereby allowing one to compare, at a later date, a running hash against the stored hash to verify that the records are authentic. In addition, as the hash values are stored in the TPM, the values cannot be tampered without subverting the hardware. For instance, when a quote is taken, the quote is signed with the TPM key, and the signing key never leaves the TPM. If the quote is altered, the signature will not validate the new (altered) quote. 
         [0030]    A TPM is a microcontroller affixed to the motherboard of a PC which stores keys, passwords, and digital certificates and performs all cryptographic functions on the chip. Alternatively, the TPM may be implemented in software. The TPM validates the stored data packets in the wiretap using integrity measurements which require a root of trust within the computing platform. In order to determine the integrity of the stored data packets, a hardware or firmware component, called the Trusted Building Block (TBB) component, takes integrity measurements at the initial boot process of the sniffer to create the Core Root of Trust for Measurement (CRTM). The CRTM is the basis of the chain of trust. All software that is executed on the sniffer is then measured and becomes part of the chain of trust. The TBB component provides trusted measurement functions (e.g. Secure Hash Algorithm-1 (SHA-1)) to the rest of the platform. A packet measurement is a hash of the complete packet, including packet headers and payload. These measurements are stored in the TPM. The hashes are stored in protected registers called Platform Configuration Registers (PCRs). For example, when a packet is received at the sniffer, the sniffer measures the entire packet. The sniffer then extends a particular PCR. The TPM extends the PCR by appending the hash value taken from the packet to the current hash value of the PCR. The extended value is then rehashed to form a composite hash value for the PCR. These extended PCR values obtained at the time of packet collection may then be used to validate the authenticity of the stored packets in the packet log. 
         [0031]    The sniffer is located at some point in the communications path between the sender and the receiver. The sniffer comprises wiretap software that is used to determine which packets traveling on the network match interest criteria and should be retained. The interest criteria used by the sniffer to determine which packets traveling on the network should be captured may include, but is not limited to, source or destination Internet Protocol addresses of the packets, keywords or phrases within the packet, as well as other packet attributes. The sniffer must have a TPM implementation and may operate either on the network with its network interface in promiscuous mode, or the sniffer may serve as the router or bridge. 
         [0032]    During sniffer start-up time, a quote (measurement) of the initial PCR values signed by the key stored in the TPM is taken by the sniffer. This initial quote is the starting PCR values hashed together to form a composite initial PCR value. For example, the initial value of a PCR is normally either “0000000000000000000000000000000000000000” or “FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF”. Alternatively, if the PCR was previously extended, an example value may comprise “ea1a3901c085941efde6f198f4b62e2fc2a6ea94”. The initial quote is signed by the TPM to allow one to verify through a digital signature that the content of the packet log is accurate and has not been tampered with. As packets arrive at the sniffer, the sniffer identifies packets which match the interest criteria. If the sniffer makes a determination that a packet should be stored, the packet may be measured by the sniffer individually, or the sniffer may group packets of interest together for speed and measurement. The measurement is stored by extending a PCR with the hash value. Intermediary quotes may be taken of the PCR values. In this manner, a PCR may be extended as many times as necessary while maintaining the packet log. When the sniffer is shut down, a final quote is taken of the PCR values, which comprises the values hashed together to form a composite final PCR value. The final quote contains the measurement of the entire packet log. 
         [0033]    When the packets are to be used as evidence in a court proceeding, the packets may be authenticated by re-running the packet log and validating that the resulting final PCR values match those from the final quote. If the calculated PCR value does not match the final quote value, then either the packet log or the quote has been tampered with since the time of collection. If the log has been tampered with, the packet log cannot be introduced as evidence in a court of law. 
         [0034]    With reference now to  FIG. 3 , a block diagram of an exemplary trusted platform architecture with which the illustrative embodiments may be implemented is shown.  FIG. 3  depicts a trusted platform architecture in accordance with the Trusted Computing Group&#39;s (TCG) PC-specific implementation specification. It should be clear to one skilled in the art that the sniffer may alternatively be based on a server, virtual, mobile phone or similar platform. 
         [0035]    System  300  supports execution of software components, such as operating system  302 , applications  304 , and drivers  306 , on its platform  308 . The software components may be received through a network, such as network  102  shown in  FIG. 1 , or may be stored, for example, on hard disk  310 . Platform  308  receives electrical power from power supply  312  for executing the software components on add-on cards  314  and motherboard  316 , which includes typical components for executing software, such as CPU  318  and memory  320 , although motherboard  316  may include multiple CPUs. Interfaces  322  connect motherboard  316  to other hardware components within system  300 , and firmware  324  contains POST BIOS (power-on self-test basic input/output system)  326 . 
         [0036]    Motherboard  316  also comprises trusted building block (TBB)  328 . Motherboard  316  is supplied by a manufacturer with TBB  328  and other components physically or logically attached and supplied by the manufacturer. TBB  328  comprises the combination of CRTM  330 , TPM  332 , the connection of CRTM  330  to motherboard  316 , and the connection of the TPM  332  to motherboard  316 . CRTM  330  is an immutable portion of the platform&#39;s initialization code that executes upon a platform reset event. 
         [0037]    Turning now to  FIG. 4 , a block diagram of an exemplary trusted platform module is shown.  FIG. 4  illustrates components of a trusted platform module, such as TPM  332  in  FIG. 3 , according to TCG specifications. As previously mentioned, TPM  400  is used in conjunction with a network sniffer to provide the capability of notarizing wiretaps. 
         [0038]    TPM  400  comprises input/output component  402 , which manages information flow over communications bus  404  by performing appropriate protocol encoding/decoding operations and routing of messages to appropriate components. TPM  400  contains cryptographic processing capabilities. TPM  400  may also be implemented on a cryptographic co-processor  406 , such as PCI-X Cryptographic Coprocessor (PCIXCC). Key generator  408  creates symmetric keys and RSA asymmetric cryptographic key pairs. HMAC engine  410  performs HMAC (Keyed-Hashing for Message Authentication) calculations, whereby message authentication codes are computed using secret keys as integrity checks to validate information. 
         [0039]    Random number generator  412  acts as a source of randomness for the computation of various values, such as keys or other values. SHA-1 engine  414  implements the SHA-1 hash algorithm. Power detector  416  manages the power states of TPM  400  in association with the power states of the platform. Opt-in component  418  maintains the state of persistent and volatile flags and enforces semantics associated with those flags such that TPM  400  may be enabled and disabled. Execution engine  420  runs program code to execute commands that TPM  400  receives through input/output component  402 . Non-volatile memory  422  stores persistent identity and state associated with TPM  400 . Non-volatile memory  422  may store static data items but is also available for storing dynamic data items by entities that are authorized by the TPM owner. Volatile memory  424  stores dynamic data items, including the Platform Configuration Registers, which are extended with the measurements of the packets of interest. 
         [0040]      FIGS. 5A and 5B  are block diagrams of known wiretapping configurations. In particular,  FIG. 5A  shows several computers linked together in a network. Computer  1   502 , computer  2   504 , and computer  3   506  are examples of data processing systems such as clients  110 - 114  in  FIG. 1  connected by a network, such as network  102 . In this illustrative example, a data packet may be transmitted from computer  1   502  to computer  2   504  or computer  3   506  via Internet Service Provider (ISP) routers  508  and  510 . However, router  512  containing a sniffer (sniffer  514 ) is placed between computers  1   502 ,  2   504 , and  3   506 . As the packet travels through router  512 , sniffer  514  captures all packets destined for computers  2   504  or  3   506  and examines the packet headers and/or content. Sniffer  514  is an “active” sniffer in that the sniffer receives packets intended for destination computers  2   504  and  3   506  and sends the packet to the destination computer after the packet header is analyzed. If a captured packet contains something of interest to the sniffer, the sniffer will first store the packet of interest in log  516  and then forward the packet to its intended destination computer, such as computers  2   504  or  3   506 . 
         [0041]    Similar to  FIG. 5A ,  FIG. 5B  shows several computers, computer  4   522 , computer  5   524 , and computer  6   526 , connected in a network. A data packet may be transmitted from computer  4   522  to computer  5   524  or computer  6   526  via ISP routers  528  and  530 . In the configuration in  FIG. 5B , however, the sniffer being used on the network is not located within a router as in  FIG. 5A , but rather sniffer  532  is a “passive” sniffer and is located on the same network segment as one of the targeted computers or one of the routers along the path to the target computers. A passive sniffer does not directly intrude onto a foreign network or computer, and the activity of a passive sniffer is not detectable by the devices being observed. While computers  5   524  and  6   526  will accept only those packets from ISP router  530  which have packet header information indicating that the packet is intended for that particular computer, sniffer  532  accepts all packets and examines the packet headers and/or content. If a captured packet contains something of interest to sniffer  532 , the sniffer will store the packet of interest in log  534 . 
         [0042]      FIG. 6  is a block diagram of an exemplary wiretapping configuration comprising a secure non-repudiable sniffer in accordance with the illustrative embodiments. The wiretapping configuration in  FIG. 6  allows for intercepting and authenticating packet traces while the packet is transmitted from the source to the destination location, in contrast with the wiretapping configurations in  FIGS. 5A and 5B  which may authenticate the packet traces after the packets are stored. The drawback to the configurations in  FIGS. 5A and 5B  is that they leave a long window of vulnerability during which time the packet traces may have been undetectably altered. In addition, the authentication provided by the wiretapping configuration in  FIG. 6  also allows for determining the router software and hardware which collected the packet trace. 
         [0043]    In this illustrative example, a data packet may be transmitted from computer  1   602  to computer  2   604  or computer  3   606  via ISP routers  608  and  610 . All packets transmitted between computer  1   602  and computers  2   604  and  3   606  are intercepted by sniffer  612 . Sniffer  612  is a secure non-repudiable sniffer in that sniffer  612  allows packet trace measurements to be taken when the packets are collected, thereby increasing the reliability of the computer records for evidence purposes. It should be noted that although sniffer  612  is an active sniffer in the particular wiretapping configuration in  FIG. 6 , the sniffer may also be implemented as a passive sniffer without departing from the spirit or scope of the illustrative embodiments. 
         [0044]    TPM  614  is an example of a trusted platform module, such as TPM  400  in  FIG. 4 . TPM  614  is connected to sniffer  612  and used to store and authenticate the trust measurements of the packets intercepted by sniffer  612 . Sniffer  612  may be placed at any point in the communications path between computer  1   602  and computer  2   604  or computer  3   606 . As a packet travels from computer  1   602  to computer  2   604 , sniffer  612  captures the packet and examines the packet header and/or content. If the captured packet contains something of interest to sniffer  612 , the sniffer will store the packet information of interest in signed log  616  and then send the packet to its intended destination computer, such as computers  2   604  or  3   606  without knowledge or consent of the computer owners. In contrast with log  516  in  FIG. 5A  and log  534  in  FIG. 5B , log  616  contains the initial quote, the intermediary quotes, and the final quotes which form the basis for the strong authentication of the log. 
         [0045]      FIGS. 7A and 7B  depict an example log file in accordance with the illustrative embodiments. In particular, log file  700  represents a log file, such as log  616  in  FIG. 6 . However, for purposes of illustration, log file  700  has been rendered human readable, and thus does not represent the actual contents of the log file in the preferred embodiment. 
         [0046]      FIG. 8  is a flowchart illustrating the sniffer logic in accordance with the illustrative embodiments. The process begins with a trusted boot of the sniffer (step  802 ). In the trusted boot, the sniffer instructs the TPM to take an initial quote of the PCRs which comprises a hash of the starting values of the PCRs. The initial quote is then signed by the TPM and provided to the packet log (step  804 ). When a packet arrives at the sniffer (step  806 ), the sniffer determines whether the packet is a packet of interest (step  808 ). This determination may be made based on a set of interest criteria such as, for example, packet header information (e.g., IP source or destination address) or the content of the packet itself. 
         [0047]    If the sniffer determines the packet is of interest (‘yes’ output of step  808 ), the sniffer then measures the packet by taking a hash of the entire packet (step  810 ). This hashed value measurement is then stored in a PCR by extending the current PCR value with the hashed value of the packet (step  812 ). The packet of interest is then stored in the packet log (step  814 ). The packet is then sent to its intended destination computer (step  816 ). 
         [0048]    Turning back to step  808 , if the sniffer determines that the packet is not of interest (‘no’ output of step  808 ), the sniffer skips to step  816  and sends the packet to its intended destination. 
         [0049]    The sniffer then makes a determination as to whether an intermediary quote should be taken of the stored packets (step  818 ). Intermediary quotes of the stored packets may be taken periodically and appended to the packet log. If the sniffer determines that an intermediary quote should not be taken (‘no’ output of step  818 ), the process continues to step  822 . However, if the sniffer determines that an intermediary quote should be taken (‘yes’ output of step  818 ), the sniffer instructs the TPM to take a quote of the PCR values and stores that quote in the packet log (step  820 ). A determination is then made as to whether the sniffer has been shut down (step  822 ). If the sniffer is not shut down (‘no’ output of step  822 ), the process loops back to step  806  and the sniffer waits for another packet to arrive. If the sniffer is shut down (‘yes’ output of step  822 ), then a final quote is taken (step  824 ), with the process terminating thereafter. The final quote of the stored packets may be appended to the packet log. 
         [0050]      FIG. 9  is a flowchart illustrating the process of validating the proof of log correctness in accordance with the illustrative embodiments. The process in  FIG. 9  may be implemented in the sniffer or may be a standalone process. 
         [0051]    The process begins with the validator reading a first quote in the log (step  902 ). The validator verifies the signature of the quote using the sniffer TPM key to determine if the signature is valid (step  904 ) via standard digital signature technique. If the signature does not validate using the sniffer TPM key (‘no’ output of step  904 ), the validator determines that the log has been tampered with (step  906 ), and the process terminates thereafter. 
         [0052]    If the signature validates using the sniffer key (‘yes’ output of step  904 ), the validator obtains the PCR values from the quote read from the log (step  908 ). The PCR values from the quote are then extended for each packet in the log (step  910 ). Subsequently, the next quote in the log is read by the TPM (step  912 ). The validator compares the signature of the next quote against the sniffer TPM key to determine if the signature is valid (step  914 ). If the signature does not validate using the sniffer key (‘no’ output of step  914 ), the TPM determines that the log has been tampered with (step  906 ), and the process terminates thereafter. 
         [0053]    If the signature validates using the sniffer TPM key (‘yes’ output of step  914 ), a determination is made as to whether the PCR values of the first quote after having been extended with the each packet in the log up to the next quote is the same as the PCR values of the next quote (step  916 ). If the PCR values are different (‘no’ output of step  916 ), the validator determines that the log has been tampered with (step  906 ), and the process terminates thereafter. 
         [0054]    If the PCR values are the same (‘yes’ output of step  916 ), then a determination is made as to whether the quote is the final quote in the log (step  918 ). If the quote is not the final quote (‘no’ output of step  918 ), the process loops back to step  910  where the PCR values are calculated for each packet in the log up to the next quote. If the quote is the final quote in the log (‘yes’ output of step  918 ), the validator determines that the entire log is valid (step  920 ), with the process terminating thereafter. 
         [0055]    The invention can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment containing both hardware and software elements. In a preferred embodiment, the invention is implemented in software, which includes but is not limited to firmware, resident software, microcode, etc. 
         [0056]    Furthermore, the invention can take the form of a computer program product accessible from a computer-usable or computer-readable medium providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable or computer readable medium can be any tangible apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. 
         [0057]    The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. Examples of a computer-readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk and an optical disk. Current examples of optical disks include compact disk-read only memory (CD-ROM), compact disk-read/write (CD-R/W) and DVD. 
         [0058]    A data processing system suitable for storing and/or executing program code will include at least one processor coupled directly or indirectly to memory elements through a system bus. The memory elements can include local memory employed during actual execution of the program code, bulk storage, and cache memories which provide temporary storage of at least some program code in order to reduce the number of times code must be retrieved from bulk storage during execution. 
         [0059]    Input/output or I/O devices (including but not limited to keyboards, displays, pointing devices, etc.) can be coupled to the system either directly or through intervening I/O controllers. 
         [0060]    Network adapters may also be coupled to the system to enable the data processing system to become coupled to other data processing systems or remote printers or storage devices through intervening private or public networks. Modems, cable modem and Ethernet cards are just a few of the currently available types of network adapters. 
         [0061]    The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.