Abstract:
A method of producing a hardware agent being a single integrated circuit encapsulated within a semiconductor device package. The method comprises the steps of generating a device-specific key pair internally within the hardware agent, and verifying that the key pair is unique. After production, secure communications are established through transmission of at least one digital certificate, followed by a successful challenge and response communication exchange.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This is a continuation of patent application (application Ser. No. 08/538,869; filed Oct. 4, 1995, now U.S. Pat. No. 5,796,890) of a parent U.S. patent application (application Ser. No. 08/251,486) filed May 31, 1994 issued into U.S. Pat. No. 5,539,828 on Jul. 23, 1996. The U.S. divisional patent application issued into Pat. No. 5,796,840 on Aug. 18, 1998. This continuation application is owned by the same assignee of the divisional patent application and its parent application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of data security. More particularity, the present invention relates to a cryptographic semiconductor device storing encryption/decryption keys at manufacture and/or subsequent to manufacture to ensure secured communications between a system incorporating the semiconductor device and a device in remote communications with the system. 
     2. Art Related to the Invention 
     In today&#39;s society, it is becoming more and more desirable to transmit digital information from one location to another in a manner which is clear and unambiguous to a legitimate receiver, but incomprehensible to any illegitimate recipients. Accordingly, such information is typically encrypted by a software application executing some predetermined encryption algorithm and is transmitted to the legitimate receiver in encrypted form. The legitimate receiver then decrypts the transmitted information for use. This encryption/decryption transmission process is commonly used in governmental applications as well as for commercial applications where sensitive information is being transmitted. 
     Often, encryption/decryption of information is accomplished through symmetric key cryptography as shown in FIG.  1 . In symmetric key cryptography, an identical key  1  (e.g., a data string commonly referred to as a “symmetric key”) is used by both a legitimate sender  2  and a legitimate receiver  3  to encrypt and decrypt a message  4  (i.e., information) being transmitted between the sender  2  and receiver  3 . Such encryption and decryption may be performed through well-known conventional algorithms in accordance with RAS formats, DES formats and the like, etc. and transmitted in encrypted form through a public domain  5  such as a conventional network, telephone lines, etc. 
     Although symmetric key cryptography is computationally simple, it requires complex key management. Basically, each sender needs a different symmetric key to communicate with each legitimate receiver, thereby making it difficult, if not impossible, to be used by businesses having a large number of employees. For example, in a business of 1000 legitimate entities (e.g., employees), a maximum of 499,500 (1000×999/2) keys would need to be managed, provided that each legitimate entity is capable of communicating with any another legitimate entity within the business. In addition, symmetric key cryptography is difficult to implement in a network or global environment because there is no secure and convenient way of transmitting the symmetric key from the legitimate sender  2  to the legitimate receiver  3 . 
     Another method of encryption/decryption is to use two separate keys (referred to as a “key pair”) in which a first key (“a public key”)  10  of the key pair is used for encryption of a message  12  from a legitimate sender  13  while a second key (“a private key”)  11  of the key pair is used by the legitimate receiver  14  for decryption of the message  12  as shown in FIG.  2 . This method is commonly referred to as “asymmetric” (or public) key cryptography. One advantage of asymmetric key cryptography is that it alleviates the burdensome key management problem associated with symmetric key cryptography. Continuing the above example, the number of key pairs required for asymmetric key cryptography is equal to 1000, the total number of legitimate entities. However, in such communications system, it is known that an illegitimate entity (e.g., commercial spy) may attempt to impersonate a legitimate entity (e.g., employee, joint-venturer, etc.) by sending fraudulent messages to another legitimate entity for the purpose of disrupting work flow or obtaining confidential information. Thus, additional protocols are usually used in the asymmetric key system to ensure message and sender authentication. 
     Authentication of the sender (i.e., verifying that the sender of a public key is, in fact, the true owner of the public key) is a problem when communications are initially established between previously unknown parties. This problem is commonly avoided by incorporating a digital certificate  15  within the transmitted message  12  as shown in FIG.  3 . The digital certificate  15  is issued by a mutually trusted authority  16  (e.g., a bank, governmental entity, trade association, etc.) so that fraudulent attempts to use another&#39;s public key  10  will simply result in unreadable messages. Such mutually trusted authority  16  depends on the parties involved. For example, two individuals employed by the same business could both trust the certificates issued by a corporate security office of the business. Employees of two independent business entities, however, would require not only the certificates from the respective security offices, but also the certificates from, for example, some industry trade organization that certifies such business entities. This digital certificate  16  methodology “binds” a public key  10  to an entity (e.g., employee). 
     In the past few years, there have been many approaches toward protecting “key” information from being obtained by unauthorized persons. One such approach is employing mechanical security mechanisms, particular for portable computers which can be more easily appropriated. For example, certain companies have introduced a “secure” laptop using a tamper-detection mechanism to erase the key material if the laptop&#39;s casing is opened without authorization. However, there are several disadvantages associated with mechanical security devices. 
     A primary disadvantage associated with mechanical security mechanisms is that they may be circumvented through reverse engineering. Another disadvantage is that mechanical security mechanisms are costly to design and fabricate. Another disadvantage is that they are subject to accidental erasure of key information. 
     As a result, a number of companies are simply relying on software applications to utilize encryption/decryption protocols. However, as technology rapidly evolves, these encryption/decryption software applications place unnecessary limitations on transmission speeds of a communication system since the speed of encrypting or decrypting information is correlated to the execution speed of the instructions. 
     This approach for employing specific hardware into the customer&#39;s system to protect such keys from disclosure is also used in the rapidly growing area of “content distribution”, namely the electronic distribution of information. Some known content distribution systems include (i) selling software via modem or other electronic means and (ii) selling portions of information distributed by compact disc (“CD”), etc. Such electronic sales often depend on the use of decryption keys to “decode” the specific data involved. For example, a customer may have free access to a CD containing many files of encrypted data, but to actually purchase a specific file, he buys the corresponding “decryption key” for that file. However, a primary problem with using specific hardware to protect the keys is that such hardware requires complete management and control by the information supplier to prevent any potential unauthorized uses. 
     BRIEF SUMMARY OF THE INVENTION 
     Based on the foregoing, it would be desirable to develop a semiconductor device at least a processing unit and a non-volatile memory element for storing a public/private key pair at manufacture and at least one digital certificate at manufacture and/or subsequently thereafter to provide more secured communication between one system incorporating the semiconductor device and comprising a processing unit, at least one memory element and a random number generator. In communication with the processing unit, the memory element(s) is (are) used for containing at least a designated key pair and at least one digital certificate. The random number generator, coupled to the processing unit, is used for generating values which are used to produce at least one key internally within the semiconductor device. Accordingly, it is an object of the present invention to provide a semiconductor device which substantially reduces the risk of accidental disclosure of the public/private key information to an illegitimate recipient. 
     Other device(s) of the present invention is to provide a semiconductor device capable of internally generating a unique public/private key pair. 
     A further object of the present invention is to provide a semiconductor device for storing the private key to prevent any usage of the private key outside the otherwise unsecured semiconductor device. 
     Yet another object of the present invention is to provide a semiconductor device for securing storage and usage of the public/private key pair within an integrated circuit to substantially prevent detection of the key pair through reverse engineering. 
     Another object of the present invention is to provide a semiconductor device storing a unique digital certificate for use in remotely (electronically) authenticating the device and identifying the specific unit. 
     Another object of the present invention is to provide a device that, through its features of uniqueness and self authentication, can perform guaranteed functions on behalf of a remote entity (such as a content distributor). 
     Other device(s) of the present invention is to provide a cost-effective device for securing data communications and storage. 
     The semiconductor device is a hardware agent comprising a processing unit for performing operations for identification purposes, a memory unit having at least non-volatile memory for storage of a unique public/private key pair and at least one digital certificate verifying the authenticity of the key pair, memory for storage of cryptographic algorithms and volatile random access memory for storage of temporary data. The hardware agent further includes an interface in order to receive information (encrypted or decrypted) from and/or transmit information to other device(s). 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention will become apparent from the following detailed description of the present invention in which: 
     FIG. 1 is a block diagram illustrating a conventional symmetric key encryption and decryption process. 
     FIG. 2 is a block diagram illustrating a conventional asymmetric key encryption and decryption process. 
     FIG. 3 is a block diagram illustrating a digital certification process from a trusted authority. 
     FIG. 4 is a block diagram of a computer system incorporating an embodiment of the present invention. 
     FIG. 5 is a block diagram of an embodiment of the present invention. 
     FIG. 6 is a flowchart illustrating the method for implementing a key pair and digital certificate into a semiconductor device. 
     FIG. 7 is a flowchart illustrating the operations of the hardware agent. 
     FIG. 8 is a flowchart illustrating remote verification of the hardware agent using second level certification. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates to a hardware agent and its associated method of operation directed toward securely storing and using a public/private key pair and at least one digital certificate within the hardware agent itself. This digital certificate may include a “device certificate” being a digital certificate provided by a manufacturer of the device signifying the legitimacy of the device and/or, a “second level certificate” being a digital certificate from a trusted third party or a collection of both certificates. In the following description, numerous details are set forth such as certain components of the hardware agent in order to provide a thorough understanding of the present invention. It will be obvious, however, to one skilled in the art that these details are not required to practice the present invention. In other instances, well-known circuits, elements and the like are not set forth in detail in order to avoid unnecessarily obscuring the present invention. 
     Referring to FIG. 4, an embodiment of a computer system  20  utilizing the present invention is illustrated. The computer system  20  comprises a system bus  21  enabling information to be communicated between a plurality of bus agents including at least one host processor  22  and a hardware agent  23 . The host processor  22 , preferably but not exclusively an Intel® Architecture Processor, is coupled to the system bus  21  through a processor bus interface  24 . Although only the host processor  22  is illustrated in this embodiment, it is contemplated that multiple processors could be employed within the computer system  20 . 
     As further shown in FIG. 4, the system bus  21  provides access to a memory subsystem  25  and an input/output (“I/O”) subsystem  26 . The memory subsystem  25  includes a memory controller  27  coupled to the system bus  21  to provide an interface for controling access to at least one memory device  28  such as dynamic random access memory (“DRAM”), read only memory (“ROM”), video random access memory (“VRAM”) and the like. The memory device  28  stores information and instructions for the host processor  22 . 
     The I/O subsystem  26  includes an I/O controller  29  being coupled to the system bus  21  and a conventional I/O bus  30 . The I/O controller  29  is an interface between the I/O bus  30  and the system bus  21  which provides a communication path (i.e., gateway) to allow devices on the system bus  21  the I/O bus  30  to exchange information. The I/O bus  30  communicates information between at least one peripheral device in the computer system  20  including, but not limited to a display device  31  (e.g., cathode ray tube, liquid crystal display, etc.) for displaying images; an alphanumeric input device  32  (e.g., an alphanumeric keyboard, etc.) for communicating information and command selections to the host processor  22 ; a cursor control device  33  (e.g., a mouse, trackball, etc.) for controlling cursor movement; a mass data storage device  34  (e.g., magnetic tapes, hard disk drive, floppy disk drive, etc.) for storing information and instructions; an information transceiver device  35  (fax machine, modem, scanner etc.) for transmitting information from the computer system  20  to another device and for receiving information from another device; and a hard copy device  36  (e.g., plotter, printer, etc.) for providing a tangible, visual representation of the information. It is contemplated that the computer system shown in FIG. 4 may employ some or all of these components or different components than those illustrated. 
     Referring now to an embodiment of the present invention as shown in FIG. 5, the hardware agent  23  is coupled to the system bus  21  to establish a communication path with the host processor  22 . The hardware agent  23  comprises a single integrated circuit in the form of a die  40  (e.g., a microcontroller) encapsulated within a semiconductor device package  41 , to protect the die  40  from damage and harmful contaminants. Of course, multiple dice may be used in lieu if a single die implementation shown herein for illustration purposes. In this example, the die  40  comprises a processing unit  42  coupled to a memory unit  43 , a bus interface  44  and a number generator  45 . The bus interface  44  enables communication between the hardware agent  23  and another device (e.g., the host processor  22 ). The processing unit  42  performs computations internally within a secured environment within the die  40  to confirm a valid connection with an authorized receiver. Such computations include executing certain algorithms and protocols, activating circuitry (e.g., the number generator  45  being preferably random in nature) for generating a device-specific public/private key pair and the like. The processing unit  42  is placed within the die  40  to prevent access of the private key through virus attack, which is a common method of disrupting a computer system to obtain its private key. 
     The memory unit  43  includes a non-volatile memory element  46  which stores the public/private key pair and at least one digital certificate therein. This non-volatile memory  46  is used primarily because it retains its contents when supply power is discontinued. The memory unit  43  further includes random access memory (“RAM”)  47  in order to store certain results from the processing unit  42  and appropriate algorithms. 
     Although the hardware agent  23  is implemented as a peripheral device on the system bus  21  for greater security, it is contemplated that the hardware agent  23  could be implemented in several other ways at the PC platform level such as, for example, as a disk controller or PCMCIA card to automatically decrypt and/or encrypt information being inputted and outputted from a hard disk. Another alternative implementation would be for the hardware agent  23  to be one component of a multi-chip module including the host processor  22  as discussed below. Furthermore, even though the hardware agent  23  is described in connection with PC platforms, it is contemplated that such hardware agent  23  could be implemented within any input/output (“I/O”) peripheral device such as within a fax machine, printer and the like or on a communication path between a computer and the I/O peripheral device. 
     Referring to FIG. 6, a flowchart of the operations for manufacturing the present invention is illustrated. First, in block  100 , the die of the hardware agent is manufactured according to any conventional well-known semiconductor manufacturing technique. Next, the die is encapsulated within a semiconductor package so as to form the hardware agent itself (block  105 ). The hardware agent is placed onto a certification system which establishes an electrical connection to the hardware agent and the certification system (block  110 ). The certification system is basically a carrier coupled to a printed circuit board for generating and receiving electrical signals for certification of the hardware agent. The certification system includes a device for storage of prior generated public keys (e.g., a database) to guarantee unique key generation. Thereafter, the certification system supplies power to the hardware agent initiating a configuration sequence. During this sequence, the random number generator generates a device-specific public/private key pair internally within the hardware agent (block  115 ). 
     The public key of the public/private key pair is output to the certification system (Step  120 ) where it is compared to the storage device of the prior generated public keys from previously manufactured hardware agents (Step  125 ). In the highly unlikely event that the public key is identical to a prior generated public key (Step  130 ), the hardware agent is signaled by the certification system to generate another such public/private key pair (Step  135 ) and continue process at Step  120 . This process ensures that each public/private key pair is unique. The storage device for prior generated public keys is updated with this new, unique public key (Step  140 ). Thereafter, in Step  145 , the certification system creates a unique device certificate by “digitally signing” the public key with the manufacturer&#39;s secret private key (in general terms, encrypting the public key with the manufacturer&#39;s private key). This certificate is input to the hardware agent (Step  150 ) and the hardware agent permanently programs the unique public/private key pair and the device certificate into its non-volatile memory (Step  155 ). At this point, the device is physically unique and is now capable of proving its authenticity. 
     Referring to FIG. 7, a flowchart of remote verification of a hardware agent is illustrated. In Step  200 , a communication link is established between a system incorporating the local (“hardware agent system”) and a remote system (e.g., a system incorporating another hardware agent or running software which communicates with the hardware agent). The hardware agent outputs its unique device certificate to the remote system (Step  205 ). Since the manufacturer&#39;s public key will be published and widely available, the remote system decrypts the device certificate to obtain the public key of the hardware agent (Step  210 ). 
     Thereafter, in block  215 , the remote system generates a random challenge (i.e., a data sequence for testing purposes) and transmits the random challenge to the local system (block  220 ). In step  225 , the hardware agent generates a response (e.g., encrypts the challenge with the private key of the hardware agent) and transmits the response to the remote system (block  230 ). Then, the remote system decrypts the response with the public key of the hardware agent as previously determined from the device certificate transmitted by the hardware agent (block  235 ). In Step  240 , the remote system compares the original challenge to the decrypted response and if identical, communications between the system and the remote system are secure and maintained (block  245 ). Otherwise, the communications are terminated (step  250 ). At this point, the remote system is ensured that it is in direct contact with a specific device (of known characteristics) manufactured by a specific manufacturer. The remote system can now direct the hardware agent to perform specific functions within the target system on the remote&#39;s behalf. The integrity of these functions and secrecy of the associated data are ensured. Such functions may include receipt and use of content distribution keys, maintenance of accounting information, etc. 
     With the emergence of content distribution along, with other information providing devices, it may become necessary to provide additional assurances that the hardware agent is not a forgery. This can be accomplished by sending the hardware agent to a reputable third party entity such as another trusted authority e.g., governmental agency, bank, trade association and the like. In a manner identical to that described above, a unique third party digital certificate of the third party entity (the “second level certificate”) is input to the hardware agent. Thereafter, the hardware agent permanently programs the second level certificate accompanied by the public/private key pair and possibly the device certificate into its non-volatile memory. As a result, the hardware agent is validated through both the device certificate and the second level certificate to guarantee validity of the hardware agent and prevent fraudulent manufacture of the hardware agent, barring unlikely collusion by the third party entity and the manufacturer of the hardware agent. 
     Referring to FIG. 8, a flowchart of remote verification of a hardware agent including authentication using a second level certificate is illustrated. In block  300 , a communication link is established between the hardware agent system and the remote system. The hardware agent outputs its unique device certificate and the second level certificate to the remote system (block  305 ). Next, the remote system decrypts the device certificate using the manufacturer&#39;s published public key to obtain the public key of the hardware agent (block  310 ). Similarly, the remote system decrypts the second level certificate using a well-published public key of the third party to obtain the public key of the hardware agent stored therein (block  315 ). 
     Thereafter, the two versions of the public key of the hardware agent are compared (block  320 ) and if the two versions are not identical, communication is terminated (block  325 ). However, if the two versions are identical, the remote system generates a random challenge and transmits the random challenge to the hardware agent (block  330 ). The hardware agent generates a response i.e., the challenge encrypted with the private key of the hardware agent (block  335 ) and transmits the response to the remote system (Step  340 ). The remote system then decrypts the response with the public key of the hardware agent previously transmitted by the hardware agent (block  345 ). As in block  350 , the remote system compares the original challenge to the decrypted response and if identical, communications between the system and the remote system are secure and maintained (block  355 ). Otherwise, the communications are terminated (block  360 ). 
     The present invention described herein may be designed in many different methods and using many different configurations. While the present invention has been described in terms of various embodiments, other embodiments may come to mind to those skilled in the art without departing from the spirit and scope of the present invention. The invention should, therefore, be measured in terms of the claims which follows.