System, method, and device for playing back recorded audio, video or other content from non-volatile memory cards, compact disks or other media

Abstract

A secure software system for a portable device or computer that provides a simple interface to the device or computer and that retrieves and dynamically decrypts keys and content from a secure media while minimizing exposure of the keys and eliminating the need for manufacturers of the device or computer to create a their own system to manage these complex processes.

1 . A method of accessing an encrypted track on a removable media with a device, the track comprising frames having content, the method comprising: 
 authorizing the media;    decrypting the track by a process comprising: 
 (a) calculating a media unique key; and thereafter  
 (b) decrypting a title key stored in the memory of the device with the media unique key; and thereafter  
 (c) decrypting a group of frames; and thereafter  
 (d) deleting the decrypted title key;  
 (e) deleting the media unique key; and  
 (f) repeating (a) through (e) until the entire track is completed.  
   
   
   
       2 . A system for enabling a device to read an encrypted file having encrypted content from a media, and to write an encrypted file having encrypted content to a media, the system comprising: 
 a computing unit, and a system memory;    interface means for receiving commands from the device;    secure dynamic decryption means configured to: 
 (a) copy an encrypted title key from the media to a memory of the device,  
 (b) decrypt the encrypted title key,  
 (c) decrypt a portion of encrypted content with the decrypted title key,  
 (d) delete the decrypted title key, and  
 (e) repeat a-d such until all of the content of the file has been decrypted, and wherein the decrypted title keys reside in and are accessible only to the secure means of the system.  
   
   
   
       3 . The system of  claim 2 , wherein the title key is in a decrypted state for the time it takes to decrypt 5 seconds or less of content in a decompressed and decoded state when played back.  
   
   
       4 . The system of  claim 2 , further comprising a digital signal processor.  
   
   
       5 . The system of  claim 2 , wherein the interface means and secure dynamic decryption means are stored in a system memory of the device.  
   
   
       6 . The system of  claim 5 , wherein the interface means and secure dynamic decryption means are executed by the computing unit.  
   
   
       7 . The system of  claim 4 , wherein the secure dynamic decryption means is stored in memory of the digital signal processor, and executed by the digital signal processor.  
   
   
       8 . The system of  claim 7 , wherein the interface means is executed by the digital signal processor.  
   
   
       9 . A system that enables a device to decrypt a file having encrypted content on a secure medium, the system comprising: 
 one or more user interface modules for receiving commands from the device;    an applications programming interface for receiving the commands from the one or more user interface modules and managing the retrieval and storage of encrypted content from the secure medium;    a security engine for decrypting the encrypted content and the one or more encrypted keys sent from the secure medium to a memory of the device, the decrypted keys used to decrypt the encrypted content, wherein 
 the one or more keys are contained in an encrypted data segment, and  
 the security engine (a) decrypts one or more of the keys, (b) decrypts a portion of the encrypted content using the one or more decrypted keys, and (c) deletes the one or more decrypted keys, and (d) repeats (a)−(c) until all portions of the content are decrypted.  
   
   
   
       10 . The system of  claim 9 , wherein the content is encoded in the AAC, MP3 or WMA format.  
   
   
       11 . The system of  claim 10 , wherein the one or more keys are in a decrypted state for the time it takes to decrypt and process less than one second to about five seconds of decoded content.  
   
   
       12 . The system of  claim 9 , wherein the data segment comprising the one or more encrypted keys is buffered and decrypted in fractional portions.  
   
   
       13 . The system of  claim 12 , wherein the fractional portion is about 512 bytes.  
   
   
       14 . The system of  claim 9 , wherein the device comprises a computing unit, system memory, and a hardware interface.  
   
   
       15 . The system of  claim 9 , wherein the device further comprises a digital signal processor.  
   
   
       16 . The system of  claim 14 , wherein the system is stored in the system memory of the device.  
   
   
       17 . The system of  claim 16 , wherein the software system stored in the system memory is executed by the computing unit.  
   
   
       18 . The system of  claim 15 , wherein the system is stored in RAM of the digital signal processor.  
   
   
       19 . The system of  claim 15 , wherein a portion of the system is stored in the system memory of the device and a portion of the system is stored in RAM of the digital signal processor.  
   
   
       20 . The system of  claim 19 , wherein the portion of the system stored in the RAM of the digital signal processor is executed by the digital signal processor.  
   
   
       21 . The system of  claim 19 , wherein the portion of the system stored in the RAM of the digital signal processor comprises the security engine.  
   
   
       22 . The system of  claim 9 , further comprising one or more engines for processing and transmitting audio, video or images, each engine comprising a secure application programming interface, the secure interface(s) for accessing the encrypted content and keys of the medium, and the non-secure interface(s) for accessing the unencrypted content of the medium.  
   
   
       23 . The system of  claim 22 , further comprising a security manager module.  
   
   
       24 . The system of  claim 23 , wherein the secure interface(s) communicate with the security manager module and module communicates with the security engine.  
   
   
       25 . The system of  claim 22 , further comprising a device driver, the security engine accessing the content and keys through the device driver.  
   
   
       26 . The system of  claim 9 , wherein the security engine further comprises a random number generator, the generator utilizing two or more system timers to create the random number.  
   
   
       27 . The system of  claim 26 , wherein the generator increases the natural frequency update of the timer ticks used to create the random number.