Abstract:
A method of operating a system on chip. The system on chip includes a controller. The method includes: receiving, at the system on chip and in a storage drive, encrypted content and an encrypted content key; storing the encrypted content and the encrypted content key in a storage device; and transmitting the encrypted content key from the controller to a first decryption module. The method further includes: decrypting the encrypted content key to generate a content key based on an identification of the system on chip; transmitting the encrypted content from the controller to a second decryption module; and decrypting the encrypted content based on the content key to generate content.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/555,432 (now U.S. Pat. No. 8,635,466), issued Jan. 21, 2014, which is a continuation of U.S. patent application Ser. No. 12/685,344 (now U.S. Pat. No. 8,230,236), filed Jan. 11, 2010, which is a continuation of U.S. patent application Ser. No. 10/796,599 (now U.S. Pat. No. 7,647,507), filed Mar. 9, 2004, which claims the benefit of U.S. Provisional Application No. 60/485,578, filed Jul. 8, 2003 and U.S. Provisional Application No. 60/489,361, filed Jul. 23, 2003. The entire disclosures of the applications referenced above are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the distribution of digital content such as audio, video, music, still pictures and the like, and more particularly to secure content distribution systems and secure hard drives. 
     BACKGROUND OF THE INVENTION 
     Digital content such as but not limited to computer software, still pictures, audio, music, and video is typically distributed using digital video (or versatile) discs (DVDs), compact discs (CDs), floppy disks, and/or via the Internet. Content providers have had a difficult time preventing piracy of their content. Typically, users store the digital content using hard drives, CDs, DVDs, floppy disks or other electronic storage media. The losses that can be attributed to piracy are well in excess of billions of dollars annually and growing at an alarming pace. Because the medium and the drive are separable, it is very difficult to defeat bit-by-bit copies of the digital content. For example, pirates of DVDs used bit-by-bit copying before the DVD encryption scheme was cracked. 
     SUMMARY OF THE INVENTION 
     A secure hard drive according to the present invention comprises a storage medium that stores encrypted digital content and corresponding encrypted content keys. A public key decryption module receives one of the encrypted content keys from the storage medium and decrypts the encrypted content key using a private key to generate a content key. A block decryption module receives the encrypted digital content corresponding to the one of the encrypted content keys from the storage medium and the content key from the public key decryption module and decrypts the encrypted content using the content key. 
     In other features, the storage medium is a magnetic storage medium. The public key decryption module and the block decryption module are implemented by a system on chip (SOC). A content player receives the decrypted digital content from the block decryption module and generates at least one of an analog output signal and a digital output signal. An identification (ID) module provides an ID. The private key and a public key are based on the ID. A controller performs buffer management and timing of read/write operations. 
     A system comprises the secure hard drive and further comprises an external host and a control interface that provides an interface between the controller and the external host. The external host is one of a computer and a portable media player. 
     In yet other features, a watermark detector communicates with an output of the content player and determines whether the analog signal that is output by the content player contains a watermark. The storage medium stores a content directory having content directory entries for the content. The public key decryption module performs digital signature verification of the content directory entry corresponding to the content that is selected for play. 
     In other features, at least one of the content directory entries contains a clear content counter that specifies a portion of the corresponding content that is not encrypted. A content distributor identification (ID) field that identifies a content distributor supplying the corresponding content. A content status field that has one of an active status and a passive status. The active status enables playback and the inactive status disables playback. A signature field for the content distributor supplying the corresponding content. A content key location field that contains a first offset value points to a content key for the selected content in a content key block stored on the storage medium. A content location field that contains a second offset value that points to the selected content in an encrypted content block stored on the storage medium. 
     In still other features, the content includes at least one of audio, video, and still pictures. The system comprises a distributed communications network and at least one content distributor that transmits encrypted content, an encrypted content key, and a content directory entry for a content selection to the secure hard drive via the external host and the distributed communications network. The storage medium contains encrypted content that is pre-stored thereon. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a functional block diagram of a secure distribution system for digital content according to the present invention; 
         FIG. 2  is a functional block diagram illustrating encryption of the digital content and the content key by the content distributor; 
         FIG. 3A  is a functional block diagram of a secure hard drive that includes a system on chip (SOC) according to the present invention; 
         FIG. 3B  is a functional block diagram that illustrates one implementation of a controller of  FIG. 3A ; 
         FIG. 4  is a functional block diagram of an exemplary implementation for signing a content directory and/or content directory entry; 
         FIG. 5  is a functional block diagram of an alternate implementation for signing a content directory and/or content directory entry; 
         FIG. 6  illustrates exemplary fields of a content directory entry; 
         FIG. 7  is a flowchart illustrating steps for downloading encrypted digital content from a content distributor; 
         FIG. 8  is a flowchart illustrating steps for allowing users to sample portions of inactive content; and 
         FIG. 9  is a flowchart illustrating steps for playing back digital content stored on the secure hard drive. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify the same elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
     The secure content distribution system according to the present invention integrates the content storage medium with the drive. Since the manufacture of hard drives is a highly specialized industry, a high level of security is provided through this integration. The present invention allows distribution of a secure personal content library with a low risk of loss of the digital content to piracy. 
     Referring now to  FIG. 1 , a secure content distribution system  10  according to the present invention is shown. The secure content distribution system  10  includes a distributed communications system  14  such as the Internet, a Bluetooth network, a local area network (LAN), a wide area network (WAN), a cellular network, a satellite network or other suitable network. One or more content distributors  18 - 1 ,  18 - 2 , . . . , and  18 -N (collectively content distributors  18 ) distribute secure digital content such as a software, video, audio, still pictures, music and the like over the distributed communications system  14 . 
     A network device  22  such as a personal computer, portable media players such as personal digital assistants (PDA), cellular phones, MP3 players, and/or other any other device communicates either wirelessly and/or directly with the content distributors  18  over the distributed communications system  14 . The network device facilitates a connection to the content distributors  18 . The network device  22  is removably connected to a portable media player  28  that includes a secure hard drive  32 . The network device  22  includes a software agent  26  such as a browser that negotiates a link with the content distributor  18  and manages the transfer of data to the secure hard drive  32 . The portable media players can also directly connect to the distributed communications system  14 . A trusted third party (TTP) distributes and authenticates public keys for the secure hard drives  32  and the content distributors  18 . The content distributor  18 - 3  may also pre-store digital content on the secure hard drive  32  with either an active status (can be played) or inactive status (cannot be played), as will be described further below. 
     Referring now to  FIG. 2 , when a consumer visits a web site of the content distributor  18 , the consumer may wish to purchase content. The content distributor  18  uses an encryption module  50  that encrypts content  54  using a content key  56 . The content key  56  is preferably a randomly selected key, although other methods for determining content keys may be used. The content key  56  is then encrypted using a public key  58  of the secure hard drive  32  that requests the content  54 . The consumer downloads encrypted content  60  and an encrypted content key  64  over the distributed communications system  14  onto the secure hard drive  32 . 
     Referring now to  FIG. 3A , the secure hard drive  32  is shown in further detail and includes a SOC  70  and a magnetic medium  72 , which stores the encrypted content  60  and the encrypted content keys  64 . While the SOC  70  is shown, components of the SOC  70  can be implemented as discrete components. As will be described below, only the SOC on the secure hard drive  32  can recover the content key  56 . The SOC  70  includes a control interface  74  that provides an external interface to a host and/or network device. The control interface  74  communicates with a controller  76 , which performs buffer management, times read/write events and performs other hard drive operations. The controller  76  may include one or more of the following components: a central processing unit (CPU), memory, a hard drive controller (HDC), a buffer manager, firmware, a universal serial bus (USB), and/or other components. 
     The controller  76  communicates with a read channel circuit  80  and a preamplifier  82 , which recover the data from the read signal that is generated by the read/write head as it passes over the magnetic medium  72 . The read signal is processed by the read channel  80  and the controller  76  to generate digital data signals. Some of the digital data signals include the encrypted content key  64 , which is output to a public key decryption module  84 . A chip ID module  86  outputs a chip ID to the public key decryption module  84 . The SOC  70  has a unique chip ID, which is used to generate a private key for the SOC  70 . The private key, in turn, is used to generate a public key for the SOC  70 . For example, the public key decryption module  80  may contains a sub-module that converts the Chip-ID to the private key. Various algorithms may be used to generate the private key. 
     The public key decryption module  84  uses the private key of the SOC  70  to decrypt the encrypted content key  64  and outputs the content key  56  to a block decryption module  90 . The controller  76  outputs the encrypted content  60  to the block decryption module  90 , which uses the content key  56  to decrypt the encrypted content  60 . The block decryption module  90  outputs the content to a content player  88 , which generates an analog and/or digital output signal that includes at least one of audio, video, still pictures, and the like. 
     The SOC  70  may optionally include a watermark detector  92  that determines whether the analog signal that is output by the content player  88  includes a watermark. The watermark includes copy control information embedded in the analog signal. In other words, the watermark detector  92  is used to defeat analog attacks such as capture and re-coding. 
     Referring now to  FIG. 3B , one implementation of the controller  76  is shown to include a serial and/or parallel interface  94  such as but not limited to serial ATA and/or Integrated Device Electronics (IDE), a hard disk controller (HDC)  96 , a buffer  98 , a spindle voice coil module (VCM)  100 , and a processor  102 . The spindle VCM  100 , which interfaces with the HDC  96  and a spindle motor  104 , controllably rotates the magnetic medium  72 . The spindle VCM  100  also interfaces with a read/write arm  106  that is used to position a magneto-resistive (MR) head  108 . A resistance of the MR head  108  varies as it passes in proximity to stored positive and negative magnetic fields on the magnetic medium  72 , which represent digital ones and zeros. The buffer  98  stores data that is associated with read/write operations and other control functions of the controller  76 . The processor  102  performs processing that is associated with the read/write operations and other functions of the controller  76 . While a specific implementation is shown for the controller  76 , skilled artisans will appreciate that there are other suitable controller configurations that are contemplated. 
     Referring now to  FIG. 4 , processing of the content directory is shown in further detail. The content distributor  18  creates a content directory and/or a content directory entry for the selected content. The content directory entry may include data such as but not limited to the title, artist, and status (active (can be played) and inactive (cannot be played)). The content directory is preferably protected by a digital signature of the content distributor  18  so that others cannot modify the fields that are stored in the content directory. 
     The content distributor  18  may use an encryption module  120  and a private key  122  to sign the content directory and/or the content directory entry. A signed content directory  126  is transmitted over the distributed communications system  14  or otherwise input to the secure hard drive  32 . For example, one implementation where the distributed communications system  14  is not used includes a secure hard drive  32  with pre-recorded content. The pre-recorded content may be inactive (cannot be played) or active (can be played). 
     The secure hard drive  32  includes a decryption module  130 , which uses the public key  132  of the content distributor  18  to generate a verified content directory  134  from the signed content directory  126 . While others may view the signed content directory  126 , they are unable to modify it. While this is an effective method for securing the content directory  124 , the signed content directory  126  is typically at least twice the size of the content directory  124 . 
     An alternate implementation for signing the content directory  124  is shown in  FIG. 5 . A one-way hash module  140  uses a hash function to generate a digest  141  from the content directory  124 . The digest is then signed with a private key of the content distributor  18  in an encryption module  142 . The plaintext content directory  124  is also transmitted or otherwise loaded on the secure hard drive  32 . The secure hard drive  32  includes a decryption module  150  that uses the public key of the content distributor  18  to recover the digest  141 . The secure hard drive  32  also includes a one-way hash module  140  that generates a calculated digest. The two digests (the recovered digest and the hash-generated digest) are compared by a comparing module  154 , which generates a valid digest signal if they match and an invalid digest signal if they do not. Both the secure hard drive  32  and the content distributor  18  preferably maintain a copy of the content directory. If the secure hard drive  32  fails, all of the digital content that is owned by the consumer can be replaced after proper verification. 
     Referring now to  FIG. 6 , an exemplary content directory entry  160  is shown. Skilled artisans will appreciate that the content directory will contain an entry for each content selection. The content directory entry  160  includes a content distributor identification (ID) field  162  that identifies the content distributor  18 . Content title and artist fields  164  and  166  describe the title of the content and name of the artist, respectively. A content status field  168  identifies whether the content is active or inactive. A clear content counter  172  specifies a predetermined portion (bits, bytes, segments and/or any other measure) at the beginning of the digital content that is not encrypted. The clear content counter  172  is specified by the content distributor  18 . 
     A key hash value field  174  contains a hash value. The encrypted content key can be hashed and the hash value can be protected by the content distributor&#39;s signature. The key hash value is used to defeat a possible hacker. For example, without this field, a hacker can purchase one content selection (active) and have other inactive content selections. The hacker could play the inactive content selections by replacing the content location and the content key location fields in the inactive content directory entries with the content location and content key location of the active content selection. A secure hard drive without the hash field may allow this to occur. If the key hash value field is used, this approach will be prevented. 
     A content distributor&#39;s signature field  176  contains the signature of the content distributor, which can be verified using the content distributor&#39;s public key. The content key location field  178  contains an offset value that points to a selected content key  180  in a content key data block  182 . A content location field  184  contains an offset value that points to encrypted content  186  in an encrypted data block  190 . The fields  178  and  184  will typically be determined by the secure hard drive  32  rather than the content distributor  18 . 
     Referring now to  FIG. 7 , typical steps that are implemented by the content distributor  18  for secure content distribution according to the present invention are shown. A consumer visits a website of the content distributor  18  in step  200 . In step  202 , the content distributor  18  determines whether the consumer purchases content. If step  202  is true, the content distributor  18  encrypts the selected digital content with the random content key and sends the encrypted content to the secure hard drive  32  in step  204 . 
     In step  208 , the content distributor  18  encrypts the content key with the public key of the secure hard drive  32  and sends the encrypted content key to the secure hard drive  32 . As can be appreciated, the encrypted content and the encrypted content key can be sent to the purchasing consumer at the same time. The content directory may be signed and sent at this time using the methods described above. In step  210 , the content distributor  18  determines whether the consumer exits the website of the content distributor. If yes, control ends. Otherwise, control returns to step  202 . 
     Referring now to  FIG. 8 , operation of the clear content counter in the secure hard drive  32  is illustrated. In step  220 , the secure hard drive  32  determines whether the user selects content for play. If not, control loops back to step  220 . Otherwise when the user selects content to be played, the secure hard drive  32  determines whether the content has a content status that is equal to active in step  222 . If true, the secure hard drive  32  plays the content in step  223 . Otherwise, control determines whether the clear content counter is greater than zero in step  224 . If not, control sends a message to the user that the content is not active and that a sample is not available in step  225 . If step  224  is true, a counter is set to zero in step  226 . In step  228 , the content is played and the counter is incremented. In step  230 , the secure hard drive  32  determines whether the counter is greater than the clear content counter. If false, control continues with step  228 . Otherwise the sample time is over when the counter exceeds the clear content counter. A message is sent to the user that the sample is over in step  234 . Additional steps and/or dialogue may be initiated with the user to solicit purchase of the sampled digital content. Steps  225  and  234  may be omitted if desired. 
     Referring now to  FIG. 9 , steps for playing back content are shown. In step  250 , control determines whether the consumer selects content for playback. If not, control loops back to step  250 . In step  252 , control retrieves the encrypted content key, the content directory entry and the encrypted content that are associated with the selected content. In step  254 , the digital signature is verified. In step  256 , control determines whether the digital signal is valid. If not, control ends in step  257 . Otherwise control continues with step  258  and the content key is decrypted with the private key of the secure hard drive  32 . In step  260 , the content is decrypted using the decrypted content key. In step  264 , an analog signal is generated from the decrypted content and is output to an audio and/video playback device. In step  266 , control determines whether a watermark is detected (when the optional watermark detector is used). If not, control ends in step  257 . Otherwise, control determines whether the selected content is over. If not, control ends in step  257 . Otherwise control loops back to step  260 . 
     There are many advantages when content is distributed using the secure hard drive  32  and the secure content distribution system  10  according to the present invention. The content distributors  18  have end-to-end control of the encryption of their digital content. The content key is not revealed to anyone else on the network other than the content distributor  18 . On the consumer side, the content key is never revealed outside of the SOC  70 . Security is not compromised even if a hacker hacks into the firmware of the secure hard drive  32 . The chip-ID is part of a very complicated chip (the SoC). Therefore, it would take a significant amount of effort to determine the chip-ID. Even if the hacker can determine the chip-ID, it is still very difficult to determine the private key from the chip-ID. For example, a keyed-hash function and/or other coding techniques can be used to generate the private key from the chip-ID. Therefore, the system cannot be compromised without breaking the encryption/decryption scheme, which is unlikely. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. For example, while the present invention is described in conjunction with magnetic storage systems, other electronic storage may be used such as memory and/or optical storage. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.