Patent Publication Number: US-2007124821-A1

Title: Information processing apparatus and encrypting/decrypting method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2005-342257, filed Nov. 28, 2005, the entire contents of which are incorporated herein by reference.  
     BACKGROUND  
      1. Field  
      One embodiment of the invention relates to an information processing apparatus which outputs copy-protected audio data and an encrypting/decrypting method.  
      2. Description of the Related Art  
      When contents which are copy-protected to prevent illegal copy are to be reproduced by a computer, data must be protected to prevent raw data generated in data processing from being copied. As a protecting method, a method of encrypting receiving/transmitting of data between modules and devices is known.  
      For example, in Jpn. Pat. Appln. KOKAI Publication No. 2003-523694, as one encrypting method, a method of adding noise is disclosed.  
      In the technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2003-523694, the method of adding noise is employed as one encrypting method. However, when noise is added, it is impossible to utilize high-quality sound recorded on, for example, an HD DVD or the like. Therefore, audio data is preferably protected by encrypting the audio data by using a key. However, when the key used in encrypting can be easily obtained, contents cannot be protected. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
      A general architecture that implements the various feature of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.  
       FIG. 1  is a perspective view showing an example of schematic configuration of a personal computer serving as an information processing apparatus according to an embodiment of the present invention;  
       FIG. 2  is a block diagram showing an example of a circuit configuration of a personal computer according to an embodiment of the present invention;  
       FIG. 3  is a block diagram showing a configuration to output copy-protected audio data; and  
       FIG. 4  is a flowchart showing a procedure of a process of outputting copy-protected audio data. 
    
    
     DETAILED DESCRIPTION  
      Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment of the invention, an information processing apparatus comprises, encrypting unit which encrypts digital audio data by using an encryption key, multiplexing unit which multiplexes information of the encryption key on a digital video signal, extracting unit which extracts the information of the encryption key multiplexed on the digital video signal, and decrypting unit which decrypts the encrypted digital audio data by using the extracted information of the encryption key.  
       FIG. 1  is a perspective view of a notebook personal computer the display unit of which is opened and a docking station serving as an expanded unit.  
       FIG. 2  is a perspective view of the computer from a rear surface side.  
      This computer  10  is constituted by a computer body  11  and a display unit  12 . In the display unit  12 , a display device constituted by a liquid crystal display (LCD)  17  is built. A display screen of the LCD  17  is positioned at almost the center of the display unit  12 .  
      The display unit  12  is provided on the computer body  11  so as to be capable of rotating freely between the opened position and the closed position. The computer body  11  has a thin-box-like housing. On an upper surface of the housing, a keyboard  13 , a power button  14  to turn on/off the computer  10 , a touch pad  15 , a touch pad control button  16 , loudspeakers  19 , and the like are arranged. On the front side of the computer body  11 , a disk insertion slot  18  of an optical disk drive which can reproduce a high definition digital versatile disc (HD DVD) is arranged.  
      Video and audio signals generated by the computer body  11  and encrypted in accordance with the high-bandwidth digital content protection (HDCP) system standard are supplied to an external digital display  200  through a cable  40  connected to a connector arranged on the rear surface of the computer body  11  and being in accordance with the high-definition multimedia interface (HDMI) standard.  
      A system configuration constituted by the computer  10  and the external digital display  200  will be described below with reference to  FIG. 2 .  
      The computer, as shown in  FIG. 2 , includes a central processing unit (CPU)  111 , a north bridge  112 , a main memory  113 , a graphics processing unit (GPU)  114 , a south bridge  119 , a BIOS-ROM  121 , a hard disk drive (HDD)  122 , an optical disk drive (ODD)  123 , an embedded controller/keyboard controller (EC/KBC) IC  124 , and the like.  
      The CPU  111  is a processor arranged to control an operation of the computer  10 . The CPU  111  executes an operating system (OS) and various application programs loaded from the HDD  122  into the main memory  113 .  
      The CPU  111  also executes a basic input output system (BIOS) program stored in the BIOS-ROM  121 . The BIOS-ROM  121  is a program for hardware control.  
      The north bridge  112  is a bridge device which connects a local bus of the CPU  111  and the south bridge  119  to each other. In the north bridge  112 , a memory controller which accesses and controls the main memory  113  is also built. The north bridge  112  also has a function of executing communication with the GPU  114  through an accelerated graphics port (AGP) bus or the like.  
      The GPU  114  is a display controller which controls the LCD  17  or the external digital display  200  used as a display monitor of the computer  10 . The GPU  114  has a video memory (VRAM). The GPU  114  generates an image signal forming a display image to be displayed on the LCD  17  or the external digital display  200  of the display unit  12  from display data written to the video memory by the OS/application programs.  
      The south bridge  119  controls various devices on a low pin count (LPC) bus. In the south bridge  119 , an integrated drive electronics (IDE) controller to control the hard disk drive (HDD)  122  and the optical disk drive (ODD)  123 , a peripheral component interconnect (PCI) controller, a USB controller, and an audio controller  30  are built.  
      The optical disk drive  123  is a drive unit to drive storage media such as an HD DVD, a DVD, or a CD. The optical disk drive  123  is a drive unit which writes data to a recordable optical medium such as a CD-R or a DVD-R and which writes/erases data to/from a rewritable optical medium such as a CD-RW, a DVD-RW, or a DVD-RAM.  
      The audio controller  130  supplies digital audio data to at least one of an audio codec  131  and an HDMI transmitter  132  depending on types of audio drivers to be used by the applications.  
      The audio codec  131  supplies an audio signal obtained by decoding (extending) audio data to the loudspeakers  19  through an analog mixer  133  to cause the loudspeakers  19  to output sound. The audio signal is supplied to an external loudspeaker connected to a line-out terminal  135  to cause the external loudspeaker to output sound. The audio codec  131  has a function of coding analog audio data input from the outside.  
      The embedded controller/keyboard controller (EC/KBC) IC  124  is a 1-chip microcomputer in which an embedded controller for power management, the keyboard (KB)  13 , the touch pad  15 , and a keyboard controller to control a touch pad control button  16  are integrated. The embedded controller/keyboard controller (EC/KBC) IC  124  has a function which powers on/off the computer  10  in cooperation with a power supply controller depending on an operation of the power button  14  by a user.  
      The HDMI transmitter  132  synthesizes the video data and the audio data generated by the GPU  114  in accordance with a scheme determined by the HDMI and generates digital data encrypted by the HDCP scheme to supply the digital data to an HDMI connector  140 . The HDMI transmitter  132  builds an audio codec therein, converts the audio data into analog data, and supplies the analog data to the analog mixer  133 . The HDMI transmitter  132  is provided as one semiconductor device. A decrypting unit  331 , a key information extracting unit  332 , and a DAC  334  are packaged in one semiconductor device.  
      The analog mixer  133  synthesizes the analog audio signal supplied from the audio codec  131  and the analog audio signal supplied from the audio codec in the HDMI transmitter  132  with each other to supply the synthesized audio signal to the loudspeakers  19 , the line-out terminal  135 , and the like.  
      The external digital display  200  has a decoder  201  to decrypt a video signal encrypted by the HDMI transmitter  132 .  
      When the computer  10  reproduces content which is copy-protected to prevent illegal copy, the computer  10  protects data to prevent raw data generated in data processing from being copied and to make it possible to make sound output from another application at the same time.  
      A configuration which protects audio data of copy-protected content and makes sound output from another application at the same time will be described below with reference to  FIG. 3 .  
      An HD DVD player  301 , a timer  304 , and a mailer  305  are applications run under on the operating system.  
      The HD DVD player  301  decrypts video data and audio data from reproduced data of an HD DVD obtained by the optical disk drive  123 . The HD DVD player  301  has a key  302  having a plurality of encryption keys and a encrypting unit  303  which encrypts audio data by using an encryption key selected from the encryption keys included in the key  302 .  
      The timer  304  has a function of making an alarm sound when a predetermined time has come. The mailer  305  has a function of transmitting/receiving mails and making a notification sound when a mail is received.  
      The digital mixer  311  is a module run under on the OS. The digital mixer  311  converts audio data received from the application/OS into data in a common format. When a plurality of audio data are simultaneously received, a plurality of audio data converted into data in a common format are mixed with each other. In Windows (trademark) available from Microsoft Corporation, a module called kmixer corresponds to the digital mixer  311 .  
      The audio controller  130  supplies audio data to the HDMI transmitter  132  or the audio codec  131  depending on a designation from audio drivers  322  and  323 .  
      A video driver  321  writes video data received from the application/OS to the video memory of the GPU  114  and controls the GPU  114 .  
      The HDMI transmitter  132  generates data depending on a scheme of the HDMI from the video signal and the audio signal and encrypts the generated data in accordance with a scheme of the HDCP.  
      The audio codec  131  decodes (extends) compressed audio data. The decoded (extended) audio data is converted into an analog audio signal by a digital-to-analog converter (DAC; first converter)  136  to obtain a signal which can be input to the loudspeakers  19  and the line-out terminal  135 .  
      A procedure of a process of outputting copy-protected audio data will be described below with reference to  FIG. 4 .  
      A copy-protected HD DVD is reproduced by the optical disk drive  123  to obtain reproduced data (step S 1 ). The reproduced data is provided to the HD DVD player  301 . The HD DVD player  301  decrypts video data and audio data from the reproduced data (step S 11  and step S 12 ). In this case, the decrypted video data and the decrypted audio data are compressed.  
      The HD DVD player  301  selects an encryption key used in encryption from a plurality of encryption keys (step S 12 ). The encrypting unit encrypts the audio data decrypted from the reproduced data by using the selected encryption key (step S 13 ).  
      The HD DVD player  301  gives the encrypted audio data to the audio driver  322 . If the audio driver  322  is altered to illegally acquire audio data, the audio data encrypted by the process in step S 13  is a random value which is meaningless for the third party who does not know the decrypting method.  
      The audio driver  322  gives the encrypted audio data to the audio controller  130  together with a designation such that the audio data is supplied to the HDMI transmitter  132 . The audio controller  130  supplies the audio data supplied from the audio driver  322  to the HDMI transmitter (HDMI XMTR)  132  (step S 14 ).  
      The HD DVD player  301  gives the video data and information of the encryption key to the video driver  321 . The video driver  321  supplies the video data and the information of the encryption key to the GPU  114 . The GPU  114  decodes (extends) the video data to generate a digital video signal which forms a display image to be displayed on the LCD  17  and the external digital display  200  (step S 22 ). The GPU  114  multiplexes the information of the encryption key on the generated digital video signal (step S 23 ). The generated digital video signal is supplied to the HDMI transmitter (HDMI XMTR)  132  (step S 24 ).  
      The key information extracting unit  332  in the HDMI transmitter (HDMI XMTR)  132  extracts key information from the video signal (step S 25 ). The HDMI transmitter  132  gives the extracted key information to the decrypting unit  331  and gives the digital video signal to an audio data/video data mixer  333 .  
      The decrypting unit  331  decrypts the encrypted audio data by using the key information extracted by the process in step S 25  and decodes (extends) the compressed audio data (step S 15 ). The decrypting unit  331  gives the decoded audio data to the audio data/video data mixer  333  and the digital-to-analog converter (DAC; second converter)  334 . The DAC  334  converts the digital audio data into an analog audio signal to supply the analog audio signal to the analog mixer  133  (step S 16 ).  
      The timer  304  supplies compressed audio data of an alarm sound to the digital mixer  311  to make an alarm sound when a predetermined time has come (step S 31 ). The mailer  305  supplies the compressed audio data of a notification sound to the digital mixer  311  to make a notification sound when a mail is received (step S 31 ).  
      The digital mixer  311  converts audio data supplied from applications of the timer  304 , the mailer  305 , and the like into data in a common format to mix the converted data (step S 32 ). The digital mixer  311  gives the mixed audio data to the audio driver  323 . The audio driver  323  gives the mixed audio data to the audio controller  130  together with a designation such that the audio data is supplied to the audio codec  131 . The audio controller  130  supplies the audio data supplied from the audio driver  323  to the audio codec (AC)  131  (step S 33 ).  
      The audio codec  131  decodes (extends) the compressed audio data (step S 34 ). The audio codec  131  supplies the decoded (extended) audio data to the HDMI transmitter (HDMI XMTR)  132  (step S 35 ).  
      The audio data/video data mixer  333  multiplexes the audio data decoded by the process in step S 15 , the audio data input by the process in step S 35 , and the video signal obtained after a key is extracted by the process in step S 25  in conformity to a scheme of the HDMI (step S 41 ). An HDCP encryption unit  335  encrypts the synthesized signal in accordance with a scheme of the HDCP (step S 42 ) and outputs the encrypted signal to the HDMI connector  140  (step S 43 ).  
      The audio codec  131  converts the digital audio data decoded (extended) by the process in step S 34  into an analog audio signal by the digital-to-analog converter (DAC; first converter)  136  (step S 36 ). The audio codec  131  supplies the analog audio signal to the analog mixer  133 .  
      The analog mixer  133  mixes the analog audio signal supplied from the audio codec  131  and the analog audio signal supplied from the HDMI transmitter  132  by the process in step S 16  with each other (step S 51 ). The analog mixer  133  outputs the mixed audio signal to the loudspeakers  19 , the line-out terminal  135 , and the like (step S 52 ).  
      When information of an encryption key used in encryption is input as a part of video data to the HDMI transmitter  132 , audio data can be analyzed without including key information in the resultant data, and video data including the information of the encryption key cannot also be easily obtained. This makes it difficult that the third party illegally obtains a key to decrypt the data. Furthermore, since the decrypting unit  331 , the key information extracting unit  332 , and the DAC  334  are packaged in one semiconductor device, information of an encryption key extracted by the key information extracting unit  332  cannot be easily obtained.  
      Therefore, encrypted data is processed in isolation from processing of audio data for an OS, and the data is converted into an analog signal and then subjected to mixing to realize compatibility between the encryption and the mixing.  
      As described above, the encrypted data is processed in isolation from processing of audio data for an OS, and the data is converted into an analog signal and then subjected to mixing to make it possible to realize compatibility between the encryption and the mixing.  
      While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.