Abstract:
A system includes a line-based receiver for receiving protected content from a source and a line-based transmitter for providing the protected content to a destination. The protected content is secure, such as by using a High-bandwidth Digital Content Protection (HDCP) mechanism. Between the line-based transmitter and receiver is a wireless transmitter and a wireless receiver. The wireless transmitter establishes an encrypted wireless link with the wireless receiver according to a second encryption mechanism. The wireless transmitter is further configured for receiving the protected content from the line-based receiver, encrypting the protected content according to the second encryption mechanism, and wirelessly transmitting the encrypted protected content. The wireless receiver is further configured for receiving the wirelessly transmitted protected content from the wireless transmitter and decrypting the protected content according to the second encryption mechanism.

Description:
CROSS REFERENCE 
     The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/896,405, which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     It is frequently desirable to provide a secure content delivery mechanism for transferring protectable subject matter from one node to another. One example of such a mechanism is the provision of digital video and/or audio over a Digital Video Interface (DVI) or High-Definition Multimedia Interface (HDMI). DVI and HDMI often use a mechanism called High-bandwidth Digital Content Protection (HDCP) to prevent the interception of the audio/video between the content source and destination. By using HDCP, data, such as copyright protectable movies and music, can be securely transmitted with a reduced likelihood of theft. 
     HDCP is required, by standard, to be delivered over a physical link, such as an HDMI cable. Furthermore, connections between two such links require the use of a repeater that provides endpoint data encryption termination to both links, and fulfills any encryption and/or key requirements for each individual link. HDCP repeaters are generally described in the document “High-bandwidth Digital Content Protection System,” Revision 1.1, Jun. 9, 2003, (hereinafter “HDCP System Standard”) which is hereby incorporated by reference into the present application in its entirety. 
     HDCP compliant devices are required, by standard, to have a unique key set (“DKS”), including 40 56-bit secret device keys, referred to as Device Private Keys, and a 40-bit identifier, referred to as the Key Selection Vector (“KSV”). During authentication, a transmitter (“Device A”) sends to a receiver (“Device B”) a message containing the transmitter&#39;s KSV (“Aksv”) and a 64-bit pseudorandom value An. Device B responds with the receiver&#39;s KSV (“Bksv”) and indicates whether Device B is a repeater. Device A verifies that Bksv has not been revoked and that it contains 20 ones and 20 zeros. Both devices then generate a session key (“Ks”), which is a 56-bit secret key for the HDCP cipher, a 64-bit secret value (“Mo”) that is used for the next phase of authentication, and a 16-bit response value (“Ro”) to indicate success of the authentication exchange. 
     If Device B is a repeater, the device gathers a list of downstream KSVs to report upstream. The KSVs are checked upstream to determine whether they have been revoked. The final step in authentication occurs during the vertical blanking period and involves both of the devices calculating new cipher initialization values Ki, Mi, and Ri, wherein the index i represents the frame number staring with 1 for the first video frame that is encrypted. 
     A general trend towards wireless links exists. However, as stated above, some transmission mechanisms, such as HDCP, cannot be provided over a wireless link. Therefore, a need exists to provide a wireless link between two nodes in which transmission mechanisms like HDCP would otherwise be provided. 
     SUMMARY 
     A system and method is provided for providing secure content between a source and destination over a wireless link. In one embodiment, the system includes a line-based receiver for receiving protected content from a source and a line-based transmitter for providing the protected content to a destination. The protected content is secure, such as by using a High-bandwidth Digital Content Protection (HDCP) mechanism. 
     Between the line-based transmitter and receiver is a wireless transmitter and a wireless receiver. The wireless transmitter establishes an encrypted wireless link with the wireless receiver according to a second encryption mechanism. An example of the encrypted wireless link is an Advanced Encryption Standard (“AES”) data link. The wireless transmitter is further configured for receiving the protected content from the line-based receiver, encrypting the protected content according to the second encryption mechanism, and wirelessly transmitting the encrypted protected content. The wireless receiver is further configured for receiving the wirelessly transmitted protected content from the wireless transmitter and decrypting the protected content according to the second encryption mechanism. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. Furthermore, all features may not be shown in all drawings for simplicity. 
         FIG. 1  illustrates a system for providing protectable content from a source to a destination. 
         FIG. 2  is a more detailed block diagram of the system of  FIG. 1  in accordance with one embodiment. 
         FIG. 3  is a more detailed block diagram of the system of  FIG. 1  in accordance with an alternative embodiment. 
         FIG. 4  is a more detailed block diagram of the system of  FIG. 1  in accordance with another alternative embodiment. 
         FIG. 5  is a flow chart illustrating operation of the embodiment illustrated in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates generally to transmission and encryption systems. It is understood, however, that the following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. 
     Referring to  FIG. 1 , a system  10  is an example of a communications network that can benefit from one or more embodiments of the present invention. The system  10  includes a source  12  of data and a destination  14  of the data. The system  10  provides a secure content delivery mechanism for protectable subject matter from the source  12  to the destination  14 . The data is provided over a link  16 , which is further described below. 
     One example of a source and destination is a compact disk (CD) player  12  providing a digital signal to an amplifier  14 , with the protectable subject matter being copyright-protectable music. Another example of a source and destination is a satellite receiver  12  providing a digital signal to a television  14 , with the protectable subject matter being copyright-protectable audio and video. Yet another example of a source and destination is a personal digital assistant  12  providing digital data to a monitor  14 , with the protectable subject matter being a table of confidential data. Still another example of a source and destination is a computer  12  providing data to a docking station  14 , with the protectable subject matter being a word-processing document. Yet another example of a source and destination is a cellular telephone  12  providing data to a network node  14 , with the protectable subject matter being a confidential voice communication. The link  16  is illustrated as being bi-directional, but can have different characteristics, depending on the application. 
     For the sake of further example, the link  16  will be described as using, at least in part, an industry standard HDCP mechanism to perform content delivery and protection via upstream (towards the source) authentication. A second example would be a Digital Transmission Content Protection (DTCP) mechanism. Continuing with the HDCP mechanism example, the link  16  may include one or more HDMI or DVI physical cables and repeaters as is well known in the industry, and additional functionality, as discussed below. 
     Referring now to  FIG. 2 , in continuation of the above-mentioned HDCP example, in one embodiment, the link  16  includes a plurality of components, including an HDCP receiver  104 , an encrypting wireless transmitter  106 , a decrypting wireless receiver  108 , and an HDCP transmitter  110 . The HDCP receiver  104  and wireless transmitter  106  are connectable via an HDCP link, such as that described above. Similarly, the wireless receiver  108  and HDCP transmitter  110  are connectable via an HDCP link. 
     In accordance with one embodiment, the wireless transmitter  106  and wireless receiver  108  are connectable via a secure wireless link  112 . In the present example, the wireless link  112  is a Certified Wireless USB Authenticated link. In an alternate embodiment, the wireless link  112  can be a WiMedia WXP Authenticated link, or other appropriate or future-developed link. The wireless link  112 , in the present example, provides a full 128-bit Advanced Encryption Standard (AES) transfer mechanism for the data being transferred. The link  16  further includes an HDCP message handling mechanism  118 . The HDCP message handling mechanism  118  is used to facilitate the necessary authentication with respect to the source  12  and the destination  14  in a manner such as that described above. 
     To the source  12  and destination  14 , the link  16  functions as an HDCP repeater. It implements and adheres to all of the rules of an HDCP repeater, as specified in the aforementioned HDCP System Standard. This includes following compliance rules, such as the requirement that decrypted HDCP content, in a usable form flowing between two endpoints, be reasonably secure. As an HDCP repeater, the link  16  generates a session key (Ks) during the HDCP authentication process. 
     The embodiment illustrated in  FIG. 2  provides a variety of protection components. For example, upstream authentication is performed using an industry standard HDCP mechanism. Similarly, authentication of all downstream devices is performed using an industry standard HDCP mechanism and in compliance with all rules applicable to an HDCP repeater. In one embodiment, the secure wireless link  112  is an AES link which may be implemented as follows. First, a Diffie-Hellman exchange may be used to establish a 2048-bit Diffie Hellman key. Next, a hash function may be used to produce a session key; for example, an AES Davies-Meyer hash function may be used to produce a 128-bit session key. HDCP procedures are used to authenticate the source side system. The session key produced by the hash function can thereby be used by the wireless link  112  to establish a secure communication channel. The wireless transmitter  106  will use the session key to encrypt data that is sent to the receiver  108 . The receiver  108  will use the session key to decrypt the data. 
     In another embodiment, as shown in  FIG. 3 , the decrypting wireless receiver  108  is integrated with the destination  14  (e.g., a computer monitor, digital television, or amplifier), thereby eliminating the need for an HDCP transmitter, such as the HDCP transmitter  110  of  FIG. 2 . In the embodiment shown in  FIG. 3 , a variety of protection mechanisms are implemented. In particular, upstream authentication is performed using an industry standard HDCP mechanism. With regard to downstream authentication, it will be noted that in this embodiment, the destination device  14  must have full HDCP authentication capabilities, including keys, such that an industry standard HDCP mechanism may be used to authenticate the destination device. The link  16  is implemented as described above with reference to the embodiment illustrated in  FIG. 1 . 
     In yet another embodiment, as shown in  FIG. 4 , the encrypting wireless transmitter  106  is integrated with the source  12  (e.g., a PDA, a satellite receiver, or a CD player), thereby eliminating the need for an HDCP receiver, such as the HDCP receiver  104  of  FIG. 2 . In the embodiment shown in  FIG. 4 , a variety of protection mechanisms are implemented. With regard to upstream authentication, it will be noted that in this embodiment, the source device  12  must have full HDCP authentication capabilities, including keys, such that an industry standard HDCP mechanism may be used to authenticate the device. Downstream authentication is performed using an industry standard HDCP mechanism. The link  16  is implemented as described above with reference to the embodiment illustrated in  FIG. 1 . Additionally, a seeded hardware functionality scan (HFS) may be performed to exercise the inner workings of the destination  14  using a portion of the Diffie Hellman key as a seed. 
       FIG. 5  is a flowchart illustrating operation of the embodiment shown in  FIG. 2 . In step  500 , industry standard HDCP mechanisms are used to perform upstream and downstream authentication of the system  10  via the HDCP message handling mechanism  118 . Additionally, the secure wireless link  112  is established, as described in detail above. In step  502 , protected content encrypted in accordance with a first encryption mechanism, which in the embodiment illustrated in  FIG. 2  is a standard HDCP encryption mechanism is transmitted to the receiver  104 . In step  504 , the encrypted protected content is transmitted to the encrypting wireless transmitter  106 , where it is further encrypted in accordance with a second encryption mechanism, such as AES. In step  506 , the encrypted protected content is transmitted via the wireless link  112  to the decrypting wireless receiver  108 . In step  508 , at the decrypting wireless receiver  108 , decryption is performed in accordance with the second encryption mechanism. In step  510 , the transmitter  110  receives the protected content, which is still encrypted in accordance with the first encryption mechanism, and delivers it to the destination  14 . 
     It will be recognized that similar steps are performed by the embodiments illustrated in  FIGS. 3 and 4 . In particular, operation of the embodiment shown in  FIG. 3  proceeds as illustrated in  FIG. 5 , except that because in the embodiment of  FIG. 3  the transmitter  110  is omitted, in steps  508 - 510 , the protected content encrypted in accordance with the first encryption mechanism is delivered to the destination  14  directly from the decrypting wireless receiver  108 . Similarly, operation of the embodiment shown in  FIG. 4  proceeds as illustrated in  FIG. 5 , except that because in the embodiment the receiver  104  is omitted, in steps  502 - 504 , the protected content encrypted in accordance with the first encryption mechanism is transmitted directly from the source  12  to the encrypting wireless transmitter  106 . 
     Each of the above-mentioned components can be implemented as computer software, electrical logic, or combinations thereof. Also, although components are shown separately in the figures, in some embodiments one or more of the components on either side of the wireless link  112  may be combined into a single integrated circuit device, or a group of devices. 
     The present disclosure has been described relative to a preferred embodiment. Improvements or modifications that become apparent to persons of ordinary skill in the art only after reading this disclosure are deemed within the spirit and scope of the application. It is understood that several modifications, changes and substitutions are intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.