Abstract:
Establishing proof of authorized receipt of information between two recipients involves a sender developing an asymmetric key pair and sending one key to each of the two recipients. A first recipient develops a challenge and sends it to the second recipient. The second recipient uses a first key to encrypt the challenge and return it to the first recipient. The first recipient decrypts the response using the second key. A correct response allows the first recipient to trust that the second recipient has an authorized copy of the information because they each have a key associated with the information that came from the sender. No prior relationship between the recipients is assumed and a public key infrastructure is not required.

Description:
BACKGROUND  
       [0001]     In many circumstances, it is important for an entity to prove ownership of information received. For example, Melissa may be reluctant to discuss a business forecast with Bob until Melissa is sure Bob was given the same information Melissa has. In a co-located office situation, Bob merely has to show Melissa a copy of the business forecast to prove ownership of the data. In some business environments numbered copies of sensitive data provide further proof of authorized ownership.  
         [0002]     The problem remains the same in networked environments where physical possession of hardcopy documents may be difficult or impossible. In some security domains, such as, within a business unit, a fully developed public key infrastructure (PKI) may allow passing signed documents between participants to prove ownership. For example, Alice may send signed copies of the business forecast to both Bob and Melissa. Bob can sign his copy and forward to Melissa. Melissa can verify Bob&#39;s signature and then Alice&#39;s signature to give herself some confidence that Bob has a received a copy from Alice. However, fully developed PKI with full time access to a certificate authority and certificate revocation list may be both expensive and difficult to maintain. This is further complicated when the entities are under different security domains (e.g. use different certificate authorities). Methods exist to handle such situations, such as cross-signed root certificates, but these are particularly difficult to manage.  
         [0003]     The situation is further complicated when applied to ad hoc networks or peer-to-peer networks that may be transient in nature and either are not part of a full PKI trust infrastructure or don&#39;t have access to such an infrastructure.  
       SUMMARY  
       [0004]     To allow proof of ownership between recipients, a sender may generate a one-time use asymmetric key pair and send one key to each recipient, along with the data of interest. When each recipient has received the data and the respective asymmetric key, the keys may be used in a challenge/response authentication process to prove to authorized ownership of the data of interest.  
         [0005]     To help ensure the integrity of the process, additional steps may be taken with respect to proper delivery of the keys as well as the use of secure channels for message delivery. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a simplified and representative block diagram of a computer network;  
         [0007]      FIG. 2  is a block diagram of a computer that may be connected to the network of  FIG. 1 ;  
         [0008]      FIG. 3  is block diagram showing message flow between a sender and two recipients of the data;  
         [0009]      FIG. 4  is a flow chart of a method of preparing and sending data and related security messages to the two recipients;  
         [0010]      FIG. 5A  is a flow chart of a method of processing the data and related security message by a first recipient;  
         [0011]      FIG. 5B  is a flow chart of a method of processing the data and related security message by a second recipient;  
         [0012]      FIG. 6  is a method for the second recipient to prove authorized receipt of the data by the first recipient; and  
         [0013]      FIG. 7  is an alternate method for the second recipient to prove authorized receipt of the data by the first recipient. 
     
    
     DETAILED DESCRIPTION  
       [0014]     Although the following text sets forth a detailed description of numerous different embodiments, it should be understood that the legal scope of the description is defined by the words of the claims set forth at the end of this disclosure. The detailed description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims.  
         [0015]     It should also be understood that, unless a term is expressly defined in this patent using the sentence “As used herein, the term ‘______’ is hereby defined to mean . . .” or a similar sentence, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term by limited, by implication or otherwise, to that single meaning. Finally, unless a claim element is defined by reciting the word “means” and a function without the recital of any structure, it is not intended that the scope of any claim element be interpreted based on the application of 35 U.S.C. § 112, sixth paragraph.  
         [0016]     Much of the inventive functionality and many of the inventive principles are best implemented with or in software programs or instructions and integrated circuits (ICs) such as application specific ICs. It is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation. Therefore, in the interest of brevity and minimization of any risk of obscuring the principles and concepts in accordance to the present invention, further discussion of such software and ICs, if any, will be limited to the essentials with respect to the principles and concepts of the preferred embodiments.  
         [0017]      FIGS. 1 and 2  provide a structural basis for the network and computational platforms related to the instant disclosure.  
         [0018]      FIG. 1  illustrates a network  10  that may be used to implement a dynamic software provisioning system. The network  10  may be the Internet, a virtual private network (VPN), or any other network that allows one or more computers, communication devices, databases, etc., to be communicatively connected to each other. The network  10  may be connected to a personal computer  12  and a computer terminal  14  via an Ethernet  16  and a router  18 , and a landline  20 . Other networked resources, such as a projector  13  and printer  15  may also be supported via the Ethernet  16  or another data network. On the other hand, the network  10  may be wirelessly connected to a laptop computer  22  and a personal data assistant  24  via a wireless communication station  26  and a wireless link  28 . Similarly, a server  30  may be connected to the network  10  using a communication link  32  and a mainframe  34  may be connected to the network  10  using another communication link  36 . In one embodiment, the server  30  may function as a presentation server for serving presentation data on the network  10 . In another embodiment, the mainframe  34  may function as a broadcast server to make available data to a large number of users, for example, corporate financial results presentations. The network  10  may be useful for supporting peer-to-peer network traffic. It should be noted that peer-to-peer network traffic may pass through intermediate hosts, including servers, proxies, routers, switches, and other elements whose role is to facilitate the transmission of data between the communicating hosts.  
         [0019]      FIG. 2  illustrates a computing device in the form of a computer  110 . Components of the computer  110  may include, but are not limited to a processing unit  120 , a system memory  130 , and a system bus  121  that couples various system components including the system memory to the processing unit  120 . The system bus  121  may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI) bus also known as Mezzanine bus.  
         [0020]     The computer  110  may also include a cryptographic unit  125 . Briefly, the cryptographic unit  125  has a calculation function that may be used to verify digital signatures, calculate hashes, digitally sign hash values, and encrypt or decrypt data. The cryptographic unit  125  may also have a protected memory for storing keys and other secret data. In addition, the cryptographic unit  125  may include an RNG (random number generator) which is used to provide random numbers. In other embodiments, the functions of the cryptographic unit may be instantiated in software or firmware and may run via the operating system.  
         [0021]     Computer  110  typically includes a variety of computer readable media. Computer readable media can be any available media that can be accessed by computer  110  and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, FLASH memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can accessed by computer  110 . Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, radio frequency, infrared and other wireless media. Combinations of any of the above should also be included within the scope of computer readable media.  
         [0022]     The system memory  130  includes computer storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM)  131  and random access memory (RAM)  132 . A basic input/output system  133  (BIOS), containing the basic routines that help to transfer information between elements within computer  110 , such as during start-up, is typically stored in ROM  131 . RAM  132  typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by processing unit  120 . By way of example, and not limitation,  FIG. 2  illustrates operating system  134 , application programs  135 , other program modules  136 , and program data  137 .  
         [0023]     The computer  110  may also include other removable/non-removable, volatile/nonvolatile computer storage media. By way of example only,  FIG. 2  illustrates a hard disk drive  141  that reads from or writes to non-removable, nonvolatile magnetic media, a magnetic disk drive  151  that reads from or writes to a removable, nonvolatile magnetic disk  152 , and an optical disk drive  155  that reads from or writes to a removable, nonvolatile optical disk  156  such as a CD ROM or other optical media. Other removable/non-removable, volatile/nonvolatile computer storage media that can be used in the exemplary operating environment include, but are not limited to, magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like. The hard disk drive  141  is typically connected to the system bus  121  through a non-removable memory interface such as interface  140 , and magnetic disk drive  151  and optical disk drive  155  are typically connected to the system bus  121  by a removable memory interface, such as interface  150 .  
         [0024]     The drives and their associated computer storage media discussed above and illustrated in  FIG. 2 , provide storage of computer readable instructions, data structures, program modules and other data for the computer  110 . In  FIG. 2 , for example, hard disk drive  141  is illustrated as storing operating system  144 , application programs  145 , other program modules  146 , and program data  147 . Note that these components can either be the same as or different from operating system  134 , application programs  135 , other program modules  136 , and program data  137 . Operating system  144 , application programs  145 , other program modules  146 , and program data  147  are given different numbers here to illustrate that, at a minimum, they are different copies. A user may enter commands and information into the computer  20  through input devices such as a keyboard  162  and cursor control device  161 , commonly referred to as a mouse, trackball or touch pad. A camera  163  , such as web camera (webcam), may capture and input pictures of an environment associated with the computer  110 , such as providing pictures of users. The webcam  163  may capture pictures on demand, for example, when instructed by a user, or may take pictures periodically under the control of the computer  110 . Other input devices (not shown) may include a microphone, joystick, game pad, satellite dish, scanner, or the like. These and other input devices are often connected to the processing unit  120  through an input interface  160  that is coupled to the system bus, but may be connected by other interface and bus structures, such as a parallel port, game port or a universal serial bus (USB). A monitor  191  or other type of display device is also connected to the system bus  121  via an interface, such as a graphics controller  190 . In addition to the monitor, computers may also include other peripheral output devices such as speakers  197  and printer  196 , which may be connected through an output peripheral interface  195 .  
         [0025]     The computer  110  may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer  180 . The remote computer  180  may be a personal computer, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements described above relative to the computer  110 , although only a memory storage device  181  has been illustrated in  FIG. 2 . The logical connections depicted in  FIG. 2  include a local area network (LAN)  171  and a wide area network (WAN)  173 , but may also include other networks. Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet.  
         [0026]     When used in a LAN networking environment, the computer  110  is connected to the LAN  171  through a network interface or adapter  170 . When used in a WAN networking environment, the computer  110  typically includes a modem  172  or other means for establishing communications over the WAN  173 , such as the Internet. The modem  172 , which may be internal or external, may be connected to the system bus  121  via the input interface  160 , or other appropriate mechanism. In a networked environment, program modules depicted relative to the computer  110 , or portions thereof, may be stored in the remote memory storage device. By way of example, and not limitation,  FIG. 2  illustrates remote application programs  185  as residing on memory device  181 .  
         [0027]     The communications connections  170   172  allow the device to communicate with other devices. The communications connections  170   172  are an example of communication media. The communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. A “modulated data signal” may be a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Computer readable media may include both storage media and communication media.  
         [0028]      FIG. 3  is a block diagram showing message flows between a sender Alice  302 , a second party Melissa  304 , and a third party Bob  306 . For convenience, a familiar cryptographic notion of named parties is used. Alice  302 , Melissa  304 , and Bob  306  may be any of the devices of  FIG. 1 , such as, but not limited to computer  12 , laptop  22 , PDA  24 , or server  32 . Additionally, the sender and recipients may be processes running on any of the physical devices, whereby the verification process described may be between two processes running on a single computer or between two or more computers.  
         [0029]     Two prerequisites are shown in  FIG. 3 . First, Alice  302  and Bob  306  have a shared secret SS. Second, Alice  302  has a private key, A PR , and Melissa  304  has a corresponding public key, A PU . It is not necessary that this public/private key pair is certified by a trusted certificate authority. The public/private key pair may be generated as part of Alice&#39;s registration into a peer-to-peer network and maybe propagated as a self-signed certificate.  
         [0030]     Alice  302  may prepare security messages for Bob  306  and Melissa  304  has detail below with respect to  FIG. 4 . When complete, Alice  302  may send the data and the security messages to Melissa  304  as shown by transmission  308 . Alice  302  may also send the data and the security messages to Bob  306  as shown by transmission  310 . Bob  306  may process the messages as detailed in  FIG. 5A . Similarly, Melissa  304  may process the messages from Alice  302  as detailed in  FIG. 5B .  
         [0031]     Bob  306  may then send a transmission  312  to Melissa  304  containing a portion of the data sent from Alice  302 . To the transmission  312  may serve as a trigger for Melissa  304  to send a challenge to Bob  306  via transmission  314 . Bob  306  may process the challenge and return response via transmission  316 . Several alternatives exist for the challenge and response between Melissa  304  and Bob  306 . Two such alternatives are shown in  FIGS. 6 &amp; 7 .  
         [0032]      FIG. 4  is a flow chart of a method  400  of preparing and sending data and related security messages to the two recipients. The methods described in  FIGS. 4-7  reliance certain characteristics of asymmetric cryptography. To remind the reader, asymmetric cryptography takes advantage of the notion that two related keys, a key pair, operate such that a first key can encrypt data and only the second key can decrypt the data. Similarly, the second key can encrypt data that can only be decrypted using the first key. Normally, in a PKI infrastructure one key is kept secret and called a private key while the other key is distributed and called a public key. Even given this distinction, the keys are functionally equivalent and the private key has no more capability than the public key.  
         [0033]      FIG. 4  shows one embodiment of actions that may be performed by Alice  302 . At block  402  and asymmetric key pair may be generated. In one embodiment, a 1024 bit may be generated using an RSA algorithm. In another embodiment, an elliptic curve algorithm may be used to generate a 160 bit key. Both the RSA and elliptic curve algorithms are known in the industry. For the purpose of this example, the keys are designated S (second party) and T (third party). At block  404 , a data payload, designated I, may be identified. At block  406  shared secret, known only to Bob  306  and Alice  302 , designated SS, may be used to calculate a value H, a hash of the shared secret SS. In one embodiment, the hash function used may be a SHA-256. At block  408 , a key, K, may be generated from H using a known key generation function, such as a PBKDF2 used with an HMAC-SHA-1.  
         [0034]     The “T” asymmetric key may be encrypted with the key K, the result designated E, at block  410 , E=encrypt (T) K . The encryption of T using key K, may be a symmetric encryption operation such as Advanced Encryption System (AES), as is known in the industry. Alice  302  may determine a lifetime for the keys T and S and may form, at block  412 , B=(E, Validfrom, Validto), the Validfrom and Validto dates or times representing the lifetime of the keys. In one embodiment, the keys are valid for one day.  
         [0035]     At block  414 , the data for Bob  306  may be prepared and sent. The complete message for Bob  306  may be designed D={{B, sign(B) K }, I}sign( )A PR . That is, the value B, the value B signed using the generated key K, and the data payload, I, all signed by Alice&#39;s private key A PR . The message D may be transmitted to Bob  306 , shown in  FIG. 3  as transmission  310 .  
         [0036]     At block  416 , the data for Melissa  304  may be prepared and sent. The complete message for Melissa  304  may be designed SD={I, S}sign( )A PR . That is, the data payload, I, and the “S” asymmetric key are signed by Alice&#39;s private key A PR .  
         [0037]      FIG. 5A  is a flow chart of a method  500  of processing the data and related security message by a first recipient, in this example, Bob  306 . Bob  306  receives data D from Alice  302  at block  502 . Bob  306  may then generate a key K={key{Hash(SS)}}. This is the same symmetric key generated by Alice  302  at block  408 ,  FIG. 4 . The key generation step may be performed at any time prior to the use of the key K. At block  506 , using the key, K, the signature of B may be checked against the value of B. Signatures may use an ECDSA-256 algorithm, known in the art. When the signature verification passes, Bob may be sure that the value of B is un-tampered and came from Alice  302 , at least to the extent the security of the shared secret SS has been maintained.  
         [0038]     At block  508 , B may be parsed into its components: E, Validfrom, and Validto. If within the validity dates, that is, after the Validfrom date/time and before the Validto date/time, the process may continue. The value of I, the data payload, may be extracted from D. E may then be decrypted using key, K, at block  510  to yield the second asymmetric key, T.  
         [0039]     With the individual data elements available and any validity checks completed, the processing may continue at block  512  where the data message D may be sent to Melissa, for example, using message transport  312  of  FIG. 3 .  
         [0040]      FIG. 5B  is a flow chart of a method  520  of processing the data send from Alice  302  to Melissa  304 . Melissa may receive the data SD from Alice at block  522 . Melissa  304  may then check the signature of SD using Alice&#39;s public key, A PU . After signature verification at block  524 , the component information in SD, the data payload, I, and the asymmetric key, S, may be extracted and stored.  
         [0041]      FIG. 6  is an exemplary method  600  for the second recipient, Bob, to prove authorized receipt of the data by the first recipient, Alice. At block  602 , Melissa may receive the message D from Bob as a continuation from block  512  of  FIG. 5A . Melissa may then verify the signature of D, as signed by Alice, using Alice&#39;s public key, A PU . Melissa may also at this time verify the information I received from Bob is consistent with the information I received from Alice at block  416  of  FIG. 4 . If the two values match, Melissa knows that Bob has a copy of the data from Alice. What remains is for Melissa to receive an assurance that Bob received the information I from Alice and not from either a third party or by some form of pilfering.  
         [0042]     Melissa may generate a challenge at block  604 . As is known in the art, the challenge may be a random number or a nonce and may include a sequence number to help prevent replay attacks. The challenge may be sent to Bob at block  606 . Bob may then receive the challenge at block  608  and encrypt the challenge at block  608  using the asymmetric key T. The response to the challenge may then be returned to Melissa. Melissa may, at block  610 , receive the challenge response. At block  612  Melissa may decrypt the challenge response from Bob using the asymmetric key S. If the decrypted response matches the challenge generated at block  604 , Melissa then has an assurance that the challenge was sent to an entity known to Alice, in this case, Bob. The assurance relies on the fact that only the T key can encrypt data readable by the S key, and because merely by possessing the T key, Melissa has a reasonable assurance that Alice gave Bob the data, I, and the key, T.  
         [0043]      FIG. 7  is an alternate method for the second recipient, Bob to prove authorized receipt of the data by the first recipient, Alice. This is a alternative form for using the cryptographic verification process described in  FIG. 6 . Again, Melissa may receive the message D from Bob at block  702  and may verify the signature using Alice&#39;s public key, A PU . Melissa may then generate a challenge at block  704 , as above, using known cryptographic techniques such as a random number or nonce. The challenge may be encrypted by Melissa at block  706  using the asymmetric key, S, and the challenge sent to Bob.  
         [0044]     At block  708 , Bob may receive the challenge and decrypt the challenge using the asymmetric key, T, that he received from Alice. Bob may then return the decrypted challenge to Melissa. At block  710 , Melissa may receive the response. Melissa may then verify, at block  712 , the response by confirming the decrypted challenge received against the original challenge generated at block  704 . When confirmed, Bob has proven to Melissa that he has the matching key, T, to Melissa&#39;s key, S. Melissa may then assume with some confidence that the data I, shared by Alice with Melissa was also shared with Bob. In one example, a subsequent conversation regarding the data I, may then be held between Bob and Melissa, without other authorization or interaction with Alice, with Melissa assured she is dealing with an authorized recipient of the data.  
         [0045]     The use of asymmetric key pairs to accompany data transmissions provides users in transient or other non-trusted environments to enable verification of relationships between recipients. This may allow parties to proceed with confidence in dealing with each other absent a known or trusted source. This may provide both users and inter-process communications to share data and collaborate with confidence even in. The methods described above are easily extensible to two-way verification and one-to-many verifications.  
         [0046]     Although the foregoing text sets forth a detailed description of numerous different embodiments of the invention, it should be understood that the scope of the invention is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only and does not describe every possibly embodiment of the invention because describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the invention.  
         [0047]     Thus, many modifications and variations may be made in the techniques and structures described and illustrated herein without departing from the spirit and scope of the present invention. Accordingly, it should be understood that the methods and apparatus described herein are illustrative only and are not limiting upon the scope of the invention.