Playing method and device of digital right managing multimedia

1. A playing method of digital right managing (DRM) multimedia in which files of DRM multimedia to be played take a page as a basic playing unit, when operation of fast-forward/fast-reverse is triggered, the playing method comprising:

determining a time duration of fast-forward/fast-reverse from a first page to a target page;

determining a number of pages of fast-forward/fast-reverse based on the time duration of fast-forward/fast-reverse;

determining a position of the target page based on the number of pages of fast-forward/fast-reverse;

calculating a key stream of the position of the target page based on prestored key data of the first page without calculating a key of a page between the first page and the target page;

decrypting ciphertext of the target page based on the calculated key stream of the position of the target page; and

decoding the decrypted target page, and starting to play from the decrypted target page,

wherein determining a number of pages of fast-forward/fast-reverse based on the time duration of fast-forward/fast-reverse includes determining a number n of pages of fast-forward/fast-reverse based on the time duration of fast-forward/fast-reverse by dividing the time duration of fast-forward/fast-reverse of n pages by a time duration of fast-forward/fast-reverse of a single page, and

wherein calculating a key stream of the position of the target page includes calculating the key stream of the position of the target page according to the prestored key data of the first page and the position of the target page.

2. The method according to claim 1 , wherein further including:

when current operation of fast-forward/fast-reverse is not completed, and another operation of fast-forward/fast-reverse is triggered, the current operation of fast-forward/fast-reverse is terminated.

3. The method according to claim 1 , wherein the fast-forward/fast-reverse is operated continuously.

4. The method according to claim 1 , wherein the step of determining a time duration of fast-forward/fast-reverse includes: determining the time duration of fast-forward/fast-reverse according to instructions of fast-forward/fast-reverse input by a user.

5. The method according to claim 1 , wherein the step of calculating a key stream of the position of the target page based on a prestored key data of the first page includes:

calculating the key data-of the target page based on the prestored key data of the first page;

calculating the key stream of the position of the target page based on the key data of the target page.

6. The method according to claim 1 , wherein the files of DRM multimedia are all-encrypted files or partially-encrypted files.

7. The method according to claim 1 , wherein media formats of the files of DRM multimedia include Windows Media Audio, Windows Media Video, Windows Advanced Systems Format, RealMedia, RealAudio, RealMedia Variable Bitrate, MP3, OGG, Lossless Audio APE, Lossless Audio Codec, or Windows Audio Waveform.

8. A playing device of digital right managing multimedia, comprising:

a decrypting device that determines a time duration of fast-forward/fast-reverse from a first page to a target page, determines a number of pages of fast-forward/fast-reverse based on the time duration of fast-forward/fast-reverse, determines a position of the target page based on the number of pages of fast-forward/fast-reverse, calculates a key stream of the position of the target page based on prestored key data of the first page without calculating a key of a page between the first page and the target page, and decrypts ciphertext of the target page based on the calculated key stream of the position of the target page; and

a decoding device that decodes the target page decrypted by the decrypting device and starts to play the decrypted target page,

wherein the decrypting device includes a decryption unit that calculates the key stream of the position of the target page according to the key data of the first page and the position of the target page, and decrypts the ciphertext of the target page based on the key stream of the position of the target page, and

wherein a number n of pages of fast-forward/fast-reverse is determined by dividing a time duration of fast-forward/fast-reverse of n pages by a time duration of fast-forward/fast-reverse of a single page.

9. The device according to claim 8 , wherein the decrypting device includes:

a controller that receives instructions of fast-forward/fast-reverse;

a calculating unit that determines the time duration of fast-forward/fast-reverse based on the instructions of fast-forward/fast-reverse from the controller, determines the number of pages of fast-forward/fast-reverse according to the time duration of fast-forward/fast-reverse, and determines the position of the target page according to the number of pages of fast-forward/fast-reverse; and

a buffering unit that prestores the key data of the first page and stores the position of the target page calculated by the calculating unit.

10. The device according to claim 9 , wherein the buffering unit includes:

a first buffer that stores the key data of the first page; and

a second buffer that stores the position of the target page calculated by the calculating unit, receives the key data of the first page from the first buffer, and sends the key data of the first page and the position of the target page to the decrypting unit.

11. The device according to claim 9 , wherein the decrypting unit includes:

a converter that receives the key data of the first page and the position of the target page from the buffering unit, converts the key data of the first page according to the position of the target page and gets the key data of the target page;

a key stream generator that calculates the key stream of the position of the target page according to the key data of the target page obtained by the converter; and

a decipherer that decrypts the ciphertext of the target page according to the key stream of the position of the target page calculated by the key stream generator.

12. The device according to claim 8 , wherein the playing device further includes a user input interface that receives instructions of fast-forward/fast-reverse from a user, and transmits the instructions to the decrypting device.

13. A playing method for digital right managing (DRM) multimedia for a fast-forward/fast-reverse process from a first page to a target page, the playing method comprising:

taking a page as a playing basic unit,

pre-storing key data of the first page,

determining a time duration of fast-forward/fast-reverse;

determining a number of pages of fast-forward/fast-reverse based on the time duration of fast-forward/fast-reverse;

determining a position of the target page based on the number of pages of fast-forward/fast-reverse;

calculating a key stream of the position of the target page based on the pre-stored key data of the first page without calculating a key of a page between the first page and the target page;

decrypting ciphertext of the target page based on the calculated key stream of the position of the target page; and

decoding the decrypted target page, and start to play from the decrypted target page,

wherein determining a number of pages of fast-forward/fast-reverse based on the time duration of fast-forward/fast-reverse includes determining a number n of pages of fast-forward/fast-reverse based on the time duration of fast-forward/fast-reverse by dividing the time duration of fast-forward/fast-reverse of n pages by a time duration of fast-forward/fast-reverse of a single page, and

wherein calculating a key stream of the position of the target page includes calculating the key stream of the position of the target page according to the prestored key data of the first page and the position of the target page.