Digital data file encryption apparatus and method and recording medium for recording digital data file encryption program thereon

Abstract

A digital data file encryption system and method where digital data encrypted to a high level and an encryption key are received and stored in a computer. The stored, encrypted digital data is decrypted on the basis of the encryption key and stored in a buffer of a predetermined size. Output digital data from the buffer is reencrypted to a low level of encryption and downloaded to a digital data playing device or a data storage medium. Therefore, a digital audio or video data file is prevented from being diverted in unencrypted form from a computer communication network when it is transmitted to a personal computer through the computer communication network and, in turn, downloaded to the digital data playing device. Further, the digital data playing device is prevented from rising in cost due to the use of simple encryption for data downloaded to the playing device.

1. A method for copy protection, comprising:
 generating a partially decrypted data unit, the partially decrypted data unit including two portions, one of the two portions is encrypted having a protection level different from the other of the two portions; and    transferring the partially decrypted data unit to a target device for further decrypting based on information used in the step of generating the partially decrypted data unit; and    further comprising the steps of:    registering a computer with a data server;    transferring encrypted data from the data server to the computer the computer generating the partially decrypted data unit in a first decryption unit of the computer; and    using a second decryption unit of the target device to further decrypt the partially decrypted data unit based on the information used in the step of generating the partially decrypted data unit.    
     
     
       2. The method of  claim 1 , wherein the two portions having the different protection levels are spaced apart at a predetermined interval on the data unit. 
     
     
       3. The method of  claim 2 , further comprising the step of storing the partially decrypted data unit in a data storage medium or a digital data player. 
     
     
       4. The method of  claim 3 , further comprising the step of reading the partially decrypted stored data unit from the data storage medium or the digital data player and reproducing the data unit at the request of a user. 
     
     
       5. The method of  claim 4 , further comprising the step of decrypting the data unit based on a predetermined encryption key, and outputting the decrypted data unit to an output line. 
     
     
       6. The method of  claim 2 , further comprising the step of decrypting a remainder of the partially decrypted data unit in the target device. 
     
     
       7. The method of  claim 1 , wherein the data unit is partially decrypted based on a predetermined encryption key. 
     
     
       8. The method of  claim 2 , wherein the predetermined interval is a multiple or divisor of a buffer size. 
     
     
       9. The method of  claim 1 , wherein the step of partially decrypting the encrypted data unit in the computer is performed at a plurality of locations spaced apart at a predetermined interval on the partially decrypted data unit. 
     
     
       10. The method of  claim 1 , further comprising the step of storing the partially decrypted data unit in a data storage medium or a digital data player. 
     
     
       11. The method of  claim 10 , further comprising the step of reading the partially decrypted stored data unit from the data storage medium and reproducing the partially decrypted data unit upon request of a user. 
     
     
       12. The method of  claim 11 , further comprising the steps of:
 sending the partially decrypted digital data unit to the digital data player;    decrypting the reencrypted data unit based on a predetermined encryption key; and    outputting the decrypted data unit to an output line of the digital data player.    
     
     
       13. The method of  claim 1 , wherein the data unit received by the target device is partially decrypted based on a predetermined encryption key. 
     
     
       14. The method of  claim 13 , further comprising the steps of:
 partially decrypting the encrypted data unit in the computer is performed independently of operating the second decryption unit in the target device.    
     
     
       15. A method for copy protection, comprising:
 receiving a data unit that has been encrypted based on a predetermined encryption key;    identifying whether or not the received data unit needs to be protected;    generating an encrypted data unit having a different encryption level or method from one used to encrypt the data unit, based on a result of the identifying step; and    transferring the generated encrypted data unit having the different encryption level or method to a target device for decrypting based on information used in the step of generating the encrypted data unit; and    further comprising the steps of:    registering a computer with a data server;    transferring the data unit from the data server to the computer;    using a first decryption unit of the computer for generating the encrypted data unit having the different encryption level or method; and    using a second decryption unit of the target device for decrypting the generated encrypted data unit having the different encryption level or method based on the information used in the step of generating the generated encrypted data unit.    
     
     
       16. The method of  claim 15 , wherein the generated encrypted data unit includes two portions having the different protection levels spaced apart at a predetermined interval on the data unit. 
     
     
       17. The method of  claim 16 , further comprising the step of storing the generated encrypted data unit in a data storage medium or a digital data player. 
     
     
       18. The method of  claim 17 , further comprising the step of reading the generated encrypted data unit from the data storage medium or the digital data player and reproducing the data unit at the request of a user. 
     
     
       19. The method of  claim 18 , further comprising the step of decrypting the data unit based on a predetermined encryption key, and outputting the decrypted data unit to an output line. 
     
     
       20. The method of  claim 16 , further comprising the step of decrypting the generated encrypted data unit in the target device. 
     
     
       21. The method of  claim 16 , wherein the step of generating the encrypted data unit is based on a predetermined encryption key. 
     
     
       22. The method of  claim 16 , wherein the predetermined interval is a multiple or divisor of a buffer size. 
     
     
       23. A method for copy protection, comprising the steps of:
 enabling a registration mode for inputting a user identification;    receiving a data unit from a storage device based on the inputted user identification information, wherein the data unit has been encrypted;    generating an encrypted data unit having a different encryption level or method from one used to encrypt the data unit; and    transferring the encrypted data unit having the different encryption level or method to a target device for decrypting based on information used in the step of generating the differently encrypted data unit; and    further comprising the steps of:    registering a computer with a data server;    transferring the data unit from the data server to the computer;    using a first decryption unit of the computer for generating the encrypted data unit having the different encryption level or method; and    using a second decryption unit of the target device for decrypting the generated encrypted data unit having the different encryption level or method based on the information used in the step of generating the generated encrypted data unit.    
     
     
       24. The method of  claim 23 , wherein the step of generating the encrypted data unit is performed at a plurality of locations spaced apart at a predetermined interval on the generated encrypted data unit. 
     
     
       25. The method of  claim 24 , further comprising the step of reading the generated encrypted data unit from the data storage medium and reproducing the generated encrypted data unit upon request of a user. 
     
     
       26. The method of  claim 25 , further comprising the steps of:
 sending the generated encrypted data unit to the digital data player;    decrypting the generated encrypted data unit based on a predetermined encryption key; and    outputting the decrypted data unit to an output line of the digital data player.    
     
     
       27. The method of  claim 23 , further comprising the step of storing the generated encrypted data unit in a data storage medium or a digital data player. 
     
     
       28. The method of  claim 23 , wherein the data unit received by the target device is encrypted based on a predetermined encryption key. 
     
     
       29. The method of  claim 23 , wherein the step of generating the encrypted data unit is performed independently of decrypting the generated encryption unit in the target device. 
     
     
       30. A method for encrypting a digital data file, comprising:
 receiving a data file from a digital data server, the data file having been encrypted in the digital data server based on a predetermined encryption key;    decrypting the data file using the predetermined encryption key;    identifying whether or not the received data file needs to be protected;    reencrypting the decrypted data file on the basis of the identified result; and    transferring the reencrypted data file to a target device,    wherein the reencrypted data file has a different level of encryption as compared to that of the received data file that was encrypted in the digital data server; and    further comprising the steps of:    registering a computer with the digital data server;    transferring the data file from the digital data server to the computer;    using a first decryption unit of the computer for generating the reencrypted data file having the different level of encryption; and    using a second decryption unit of the target device to decrypt the reencrypted data file having the different level of encryption based on the information used in the step of reencrypting the decrypted data file.    
     
     
       31. A method for managing content data, the method being performed by at least one playing device and comprising:
   receiving content data from an external source device, the content data being encrypted by a first encryption method;        controlling a duration time for the content data based on an identifying operation, the content data being available on a buffer of the playing device for the duration time, and the identifying operation determining whether or not the duration time for the content data is controlled based on protection information associated with the content data;        determining whether or not to change the first encryption method based on the protection information associated with the content data; and        changing the first encryption method into a second encryption method for the content data when the determining step determines the first encryption method is to be changed into the second encryption method,        wherein the second encryption method is different from the first encryption method and is selected among a plurality of predetermined encrypting methods such that an external target device can decrypt the content data encrypted by the second encryption method.      
     
     
       32. The method of  claim 31 , wherein a size of the buffer is changed for the controlling the duration time.  
     
     
       33. The method of  claim 31 , wherein the changing step comprises:
   decrypting the content data being encrypted by the first encryption method; and        re - encrypting the decrypted content data by the second encryption method.      
     
     
       34. The method of  claim 33 , further comprising:
   transmitting the content data being re - encrypted by the second encryption method to the external target device.      
     
     
       35. An apparatus for managing content data, the apparatus comprising:
   a buffer;        a controller programmed to:        receive content data from an external source device, the content data being encrypted by a first encryption method;        control a duration time for the content data based on an identifying operation, the content data being available in the buffer of the playing device for the duration time, and the identifying operation determining whether or not the duration time for the content data is controlled based on protection information associated with the content data;        determine whether or not to change the first encryption method based on the protection information associated with the content data; and        change the first encryption method into a second encryption method for the content data when the first encryption method is determined to be changed into the second encryption method,        wherein the second encryption method is different from the first encryption method and is selected among a plurality of predetermined encrypting method such that an external target device can decrypt the content data encrypted by the second encryption method.      
     
     
       36. The apparatus of  claim 35 , wherein the controller is programmed to change a size of the buffer for controlling the duration time.  
     
     
       37. The apparatus of  claim 35 , further comprising:
   a decryptor programmed to decrypt the content data being encrypted by the first encryption method; and        an encryption unit programmed to re - encrypt the decrypted content data by the second encryption method.      
     
     
       38. The apparatus of  claim 37 , wherein the controller is further programmed to transmit the content data being re- encrypted by the second encryption method to the external target device.