Encoder and decoder

• US 5,838,791 A
• Filed: 08/09/1995
• Issued: 11/17/1998
• Est. Priority Date: 08/10/1994
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Hasebe, Takayuki, Takenaka, Masahiko, Matsuda, Masahiro, Iwayama, Noboru, Torii, Naoya
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US08/512,909
• Time in Patent Office: 1,196 Days
• Field of Search: 380/20, 380/37, 380/99, 380/50, 386/112
• US Class Current: 380/217
• CPC Class Codes: G06T 9/008 Vector quantisation
• CPC Class Codes: H04N 5/85 on discs or drums
• CPC Class Codes: H04N 7/1675 Providing digital key or authorisation information for generation or regeneration of the scrambling sequence pseudo-random number generators in general G06F7/58
• CPC Class Codes: H04N 9/8042 involving data reduction

Abstract

The present invention was made in order to provide a technology capable of safely ciphering compressed and encoded image data irrespective of lines or media and carrying out a correct decoding operation without any shifts in the frames of ciphered moving pictures.

Further, so as to prevent giving any means of encoding from comparison of image ciphered data and so as to generate totally different ciphered image data from the same data compressed images, a processing is executed not on an ECB mode but on such modes as CBC, CFB, OFB or the like. Moreover, as an initial vector, information different for frames included in a header, that is, time information from the start of an image or a frame sequential number, is used. In this way, even if compressed images within adjacent frames are accidentally the same, totally different ciphered data can be obtained.

Claims

1. An encoder comprising:

compressing and encoding means for compressing and encoding original data to produce compressed and encoded data in an input order;

data length obtaining means for carrying out frame analysis in the input order of the compressed and encoded data and obtaining a frame data length;

header generating means for generating a header storing synchronous patterns;

ciphering processing means for ciphering the compressed and encoded data to generate ciphered and compressed data; and

data assembling means for assembling the header obtained by said header generating means, the frame data length and the ciphered and compressed data into a frame.

5. The encoder of claim 1, wherein when data are sequentially ciphered by block units, if length of data to be lastly ciphered does not reach the last block length, this block is not processed by said ciphering processing means.

10. The encoder of claim 1, wherein the compressed and encoded data are MPEG data.

2. A decoder comprising:

header obtaining means for receiving data including synchronous patterns, frame data length data registering the frame data length of stored data and ciphered and compressed data, reading said synchronous patterns and obtaining a header;

frame data length obtaining means for reading said frame data length;

counter holding the frame data length obtained by said frame data length obtaining means;

deciphering means for sequentially deciphering said ciphered and compressed data based on the value of said counter, without said deciphering depending on frame analysis or unpacking compressed data; and

expansion processing means for expanding compressed data from the decoding means.

3. An encoder comprising:

compressing and encoding means for compressing and encoding original data to produce compressed and encoded data;

header generating means for generating a header storing synchronous patterns;

ciphering processing means for ciphering the compressed and encoded data and generating ciphered and compressed data;

bit inserting means for monitoring said ciphering processing means and inserting a dummy bit into the synchronous patterns when the synchronous patterns in the ciphered and compressed data are detected; and

data assembling means for assembling said obtained header and said ciphered and compressed data.

4. A decoder comprising:

header obtaining means for receiving data including synchronous patterns and ciphered and compressed data with a dummy bit inserted thereinto and obtaining a header by reading the synchronous patterns;

comparing means for comparing the ciphered and compressed data having the dummy bit inserted thereinto with substituted data in said decoder and skipping the ciphered and compressed data when the dummy bit is detected;

deciphering means for sequentially decoding the ciphered and compressed data and obtaining compressed data; and

expansion processing means for expanding compressed data from said deciphering means.

6. A method of encoding image data, comprising:

compressing and encoding the image data and storing the result into a first buffer;

analyzing frames of the image data and storing a header containing a result of said analyzing into a second buffer;

encrypting said image data in the first buffer and storing encrypted data into the second buffer to form a frame with the header;

storing the frame and header into an image data storing circuit upon completion of encryption;

attaching to the frame and header in the image data storing circuit an identifier indicating a frame sequence, and a ciphering flag indicating encryption status; and

determining a length of the frame and storing the length in the header.

7. A memory medium storing a frame of image data, comprising:

a header part containing information on the frame of the image data;

an ID part holding an identifier for the frame of the image data;

a frame length part containing a length of the image data;

a ciphered flag indicating an encryption status of the image data; and

a ciphering compressed image data part containing the image data which has been ciphered and compressed.

8. A memory medium storing a frame of image data, comprising:

a header part containing information on the image data;

an ID part containing an identifier for the frame of the image data;

a ciphered flag indicating an encryption status of the image data;

a ciphering compression image signal part holding the image data which has been ciphered and compressed; and

a synchronizing pattern derived from the image data, composed of a 1 bit inserted between a first synchronizing code and a second synchronizing code.

9. A memory medium storing a frame of image data, comprising:

a header part containing information on the image data;

a frame length part containing a length of the image data; and

a synchronizing pattern derived from the image data, composed of a 1 bit inserted between a first synchronizing code and a second synchronizing code.