Method for preventing copying of digital video disks

• US 6,167,136 A
• Filed: 05/16/1997
• Issued: 12/26/2000
• Est. Priority Date: 05/16/1997
• Status: Expired due to Term

• Current Assignee: SafeNet Incorporated (Thales SA)
• Original Assignee: Software Security, Inc. (Thales SA)
• Inventors: Chou, Wayne W.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US08/857,243
• Time in Patent Office: 1,320 Days
• Field of Search: 380/4, 380/5, 380/9, 380/10, 380/43, 380/49, 380/50, 380/46, 380/3, 380/200-210, 380/216, 380/217, 380/236-239, 380/252, 380/255, 380/277, 380/278, 380/287, 360/60, 713/189, 713/193, 713/194, 713/200
• US Class Current: 380/201
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/0021 involving encryption or decryption of contents recorded on or reproduced from a record carrier
• CPC Class Codes: G11B 20/00333 the key being stored in header data, e.g. in sector headers
• CPC Class Codes: G11B 20/00826 wherein a spoiler signal is added to degrade the signal quality
• CPC Class Codes: G11B 20/00876 wherein physical copy protection means are attached to the medium, e.g. holograms, sensors, or additional semiconductor circuitry
• CPC Class Codes: H04N 2005/91364 the video signal being scrambled
• CPC Class Codes: H04N 5/85 on discs or drums
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection

Abstract

A method for securely storing analog or digital data on a data storage medium. An analog information signal is combined with a noise signal. The composite noise and information signal is encrypted with a key which is derived from the noise signal. The encrypted composite signal is compressed and then recorded on the data storage medium along with an encrypted value of the key. The storage medium data is read, decompressed, and decrypted using a decryption key derived from the stored encrypted key. The data is then converted to an analog signal and combined with a noise correction signal derived from said key to eliminate the noise signal added to the analog information signal before storing the signal on the data storage medium.

Claims

1. A method for securely storing a series of frames of analog information which occur at a synchronous rate comprising:

generating an analog noise signal;

sampling said analog noise signal at said synchronous rate to produce a sample each frame;

combining each sampled noise signal with said analog information signal of each frame to produce a combined signal;

digitizing said combined signal;

deriving a digital representation of said sampled analog noise signal;

encrypting said digitized combined signal; and

creating a plurality of frames of said encrypted digitized signal, each frame having a header with a frame identification field and said digital representation of said sampled noise signal; and

storing said plurality of frames of said encrypted digitized signal on a data storage medium.

2. The method according to claim 1 further comprising:

encrypting said digital representation of said sampled noise.

3. The method according to claim 1 further comprising:

compressing said combined digitized signal.

4. The method according to claim 1 wherein said step of combining said analog information signal with said sampled noise signal is implemented by mixing said sampled noise signal with said analog information signal.

5. The method according to claim 1 wherein said frames of analog information signal are lines of a video signal, and said sampling is synchronized to the video signal line rate.

6. The method according to claim 1 further comprising generating a frame number based on a number of consecutive sampling intervals.

7. The method according to claim 6 further comprising inserting said frame number in said frame identification field.

8. The method according to claim 1 wherein said digital representation of said noise signal is encrypted before storing in said header.

9. A method for recovering analog information from a data medium comprising:

reading digital data stored as frames on said data medium;

deriving a key from data contained in each frame on said data medium derived from a noise component of said digital data;

decrypting said digital data with said key;

converting said digital data to an analog signal; and

combining said key derived from a noise component with said analog signal to remove noise contained in said analog signal.

10. The method according to claim 9 further comprising:

decompressing said digital data.

11. The method according to claim 9 wherein said key is converted to an analog quantity before it is combined with said analog signal.

12. An apparatus for securely storing analog information as occurring in frames at a synchronous rate comprising:

a source of analog video signals comprising a synchronous sequence of frames;

a sample and hold circuit, connected to operate in synchronism with said analog signal, said sample and hold circuit being connected to a noise generator for providing a sample of noise for each frame of the video signal;

means for combining the value of noise derived from said sample and hold circuit with each frame of said analog video signal;

means for converting said combined analog video signal and sample of noise signal to a digital signal;

means for converting said sample of noise signal into a digital encryption key;

means for encrypting said combined video signal and noise signal with said key forming a frame of encrypted data;

means for inserting a frame number and a value of said key in a header of a frame of said encrypted data; and

means for storing each of said frames on the medium.

13. The apparatus of claim 12 further including a key encryption means for encrypting said key before inserting in said header.

14. A system for decrypting frames of encrypted video information stored on a recording medium comprising:

a reader circuit for reading each frame of stored video signals;

a decoder for recovering from a header on each read frame an encrypted key, and frame number;

means for deriving a decyrption key from said encrypted key and frame number;

means for decrypting information stored within said frame containing said encryption key with said decryption key;

means for converting said decryption key into an analog voltage;

means for converting said decrypted information into an analog voltage; and

means for combining said analog voltages to produce an analog video signal.

15. The apparatus of claim 14 further comprising means for decompressing said decrypted data.