EP1095517A1 - Systeme de brouillage multimedia adaptatif (mass) - Google Patents

Systeme de brouillage multimedia adaptatif (mass)

Info

Publication number
EP1095517A1
EP1095517A1 EP99919913A EP99919913A EP1095517A1 EP 1095517 A1 EP1095517 A1 EP 1095517A1 EP 99919913 A EP99919913 A EP 99919913A EP 99919913 A EP99919913 A EP 99919913A EP 1095517 A1 EP1095517 A1 EP 1095517A1
Authority
EP
European Patent Office
Prior art keywords
samples
sample
scrambled
scrambling
lsbs
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP99919913A
Other languages
German (de)
English (en)
Inventor
S. Katherine Lam
Kamran Moallemi
Chong U. Lee
Taku Katoh
Naoki Endoh
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Verance Corp
Original Assignee
Solana Technology Development Corp
Verance Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Solana Technology Development Corp, Verance Corp filed Critical Solana Technology Development Corp
Publication of EP1095517A1 publication Critical patent/EP1095517A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/80—Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
    • H04N21/83—Generation or processing of protective or descriptive data associated with content; Content structuring
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K1/00—Secret communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/06—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols the encryption apparatus using shift registers or memories for block-wise or stream coding, e.g. DES systems or RC4; Hash functions; Pseudorandom sequence generators
    • H04L9/065—Encryption by serially and continuously modifying data stream elements, e.g. stream cipher systems, RC4, SEAL or A5/3
    • H04L9/0656—Pseudorandom key sequence combined element-for-element with data sequence, e.g. one-time-pad [OTP] or Vernam's cipher
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
    • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
    • H04N21/234—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs
    • H04N21/2347—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs involving video stream encryption
    • H04N21/23476—Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs involving video stream encryption by partially encrypting, e.g. encrypting the ending portion of a movie
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/44—Processing of video elementary streams, e.g. splicing a video clip retrieved from local storage with an incoming video stream or rendering scenes according to encoded video stream scene graphs
    • H04N21/4405—Processing of video elementary streams, e.g. splicing a video clip retrieved from local storage with an incoming video stream or rendering scenes according to encoded video stream scene graphs involving video stream decryption
    • H04N21/44055—Processing of video elementary streams, e.g. splicing a video clip retrieved from local storage with an incoming video stream or rendering scenes according to encoded video stream scene graphs involving video stream decryption by partially decrypting, e.g. decrypting a video stream that has been partially encrypted
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client 
    • H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
    • H04N21/633—Control signals issued by server directed to the network components or client
    • H04N21/6332—Control signals issued by server directed to the network components or client directed to client
    • H04N21/6334—Control signals issued by server directed to the network components or client directed to client for authorisation, e.g. by transmitting a key
    • H04N21/63345—Control signals issued by server directed to the network components or client directed to client for authorisation, e.g. by transmitting a key by transmitting keys
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/16—Analogue secrecy systems; Analogue subscription systems
    • H04N7/167—Systems rendering the television signal unintelligible and subsequently intelligible
    • H04N7/1675—Providing digital key or authorisation information for generation or regeneration of the scrambling sequence
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L2209/00—Additional information or applications relating to cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
    • H04L2209/60—Digital content management, e.g. content distribution

Definitions

  • the present invention relates to a method and apparatus for scrambling digital samples of multimedia data, e.g., such as audio or video data samples, such that the content of the samples is degraded but still recognizable.
  • multimedia data e.g., such as audio or video data samples
  • the invention is suitable for use with digital broadcast streams and digital storage media, such as compact discs (CDs) and digital video discs (DVDs) .
  • CDs compact discs
  • DVDs digital video discs
  • the number of least significant bits (LSBs) scrambled in each sample is selected such that the scrambled samples are degraded but still recognizable.
  • Schemes for communicating and storing digital data have become increasingly popular, particularly in the mass consumer market for digital audio, video, and other data. Consumers may now send, receive, store, and manipulate digital television, audio and other data content, such as computer games and other software, stock ticker data, weather data and the like. This trend is expected to continue with the integration of telephone, television and computer network resources .
  • the distance of transit can be half way around the world, as with delivery on the Internet, or millimeters, such as within a DVD player's internal data transfer from disc to DAC (Digital to Analog Converter) .
  • DAC Digital to Analog Converter
  • the scrambling key prefferably associated with the scrambled data to allow the scrambling key to be easily changed without modifying the player (e.g., DVD or CD player) on which the data is played.
  • the scrambled data should not damage the video or audio equipment even if it is played through any video or audio playback system. Some randomly scrambled waveforms can result in such damage, e.g., to speakers or circuitry.
  • the scrambled data could be any conceivable digital data. It would be desirable for the data to be scrambled at any time, including, for example, when the data signal is created (e.g., during a recording session for an audio track) , when the data signal is being distributed (e.g., during a broadcast, or during manufacture of storage media such as compact discs), or when the data is being played (e.g., on a player in a consumer's home) .
  • the present invention provides a system having the above and other advantages .
  • a method for protecting digital samples of content from illicit use by scrambling the content wherein each sample includes a plurality of bits, ranging from least significant bits (LSBs) to most significant bits.
  • the method includes the step of scrambling a number of LSBs in each sample according to a scrambling key, while preserving a number of MSBs in each sample, to provide corresponding scrambled samples.
  • the number of LSBs scrambled in each sample is provided such that the scrambled samples are degraded but still recognizable .
  • the number of LSBs to be scrambled in each sample may be adaptively determined according to the dynamic range of the sample.
  • the number of LSBs to be scrambled in each sample may be adaptively determined according to the particular frame a sample is in, where different frames can have a different number of LSBs scrambled.
  • the scrambling key may be a pseudo-random scrambling key, for example.
  • the LSBs may be scrambled within the same sample using intra-sample scrambling.
  • the LSBs may be scrambled between different samples using inter- sample scrambling.
  • inter-sample scrambling is horizontal inter-sample scrambling, where bits having the same weight are interchanged between samples .
  • the scrambling key may be embedded into the scrambled samples for use at a decoder in descrambling the scrambled samples.
  • the scrambling key for a current frame of scrambled samples may be embedded into a previous frame of samples. This avoids a delay in recovering the key at the decoder.
  • a corresponding descrambling method, and corresponding apparatuses are also presented.
  • FIG. 1 illustrates adaptive bit modification for successive data samples in successive data frames in accordance with the present invention.
  • FIG. 2(a) illustrates intra-sample scrambling in accordance with the present invention.
  • FIG. 2(b) illustrates original, unscrambled samples .
  • FIG. 2(c) illustrates the samples of FIG. 2(b) after horizontal, inter-sample scrambling in accordance with the present invention.
  • FIG. 3 illustrates a data scrambler and scramble key encoder in accordance with the present invention.
  • FIG. 4 illustrates a data descrambler and scramble key decoder in accordance with the present invention.
  • FIG. 5 illustrates a detailed data scrambler in accordance with the present invention.
  • FIG. 6 illustrates a detailed data descrambler in accordance with the present invention.
  • FIG. 7 illustrates adaptive bit modification with a fixed minimum dynamic range for successive data samples in successive data frames in accordance with the present invention.
  • the present invention relates to a method and apparatus for scrambling digital samples of multimedia data.
  • This subject matter discussed in the following patents and patent applications, each of which is incorporated herein by reference, may be adapted for use with the present invention: U.S. Patent 5,822,360, entitled “Method and Apparatus for Transporting Auxiliary Data in Audio Signals”; application no. 08/764,096, filed December 6, 1996 entitled “Method and Apparatus for Embedding Auxiliary Data in a Primary Data Signal”; U.S. Patent 5,687,191, entitled “Post Compression Hidden Data Transport”; application no. 08/912,434, filed August 18, 1997, entitled “Post Compression Hidden Data Transport for Video”; U.S.
  • Patent 5,719,937 entitled “Multi-Media Copy Management System”; application no. 08/977,719, filed November 25, 1997, entitled “Multi-Media Copy Management System”, and application no. , filed , entitled “Digital Hidden Data Transport” .
  • Similar systems for providing embedded information may also be adapted for use with the present invention. Audio, video or other digital content is scrambled to degrade its quality, but still allow a listener, viewer, or other user to recognize the content .
  • Selective scrambling of a content waveform consists of preservation of some of the MSBs (up to and including the sign bit) and scrambling of some or all of the remaining LSBs.
  • the scrambling noise is maintained at a desired level compared to the original data (e.g., audio, video or other data) .
  • Each data sample's M most significant bits are dynamically preserved. The number M can be chosen before processing begins as a preset parameter, or can vary during processing.
  • Dynamic preservation of MSBs involves performing amplitude range detection on each sample and preserving (or masking) M of the most significant bits within the range of the sample, as shown in Figure 1.
  • M may vary from 0 to the full dynamic range of the digitized samples.
  • M is the number of bits preserved in each sample's dynamic range and can be varied (for example, frame to frame) during processing.
  • M can be part of the information embedded in the content material for the decoder to use.
  • the digital content samples may be in any conceivable compressed or uncompressed digital format, including Pulse Code Modulation (PCM) samples, samples in floating point representation, samples in companding schemes (e.g., ⁇ -law and A- law) , and other compressed bit streams as described below.
  • PCM Pulse Code Modulation
  • a group of uncompressed signal samples are represented by a group of frequency samples, which are quantized according to the perceptual criteria for efficient storage and transmission.
  • the ratio between the number of frequency samples required to represent the number of signal samples are usually fixed, e.g., at one. However, the number of frequency samples actually selected for transmission may be less, since some of the perceptually unimportant frequency samples are often not transmitted.
  • This can be determined by extracting the bit allocation information contained in the compressed bit stream.
  • the frequency samples that are not transmitted usually have zero bits allocated, or otherwise indicated as zeros (e.g., a run length is indicated for a series of zeros) .
  • a binary representation of the frequency samples can be extracted with an augmentation information that indicates the number of bits allocated, dynamic range of the frequency 10
  • the process of partial scrambling is no differen than the process that applies to the uncompressed domain signal samples, e.g., as with a PCM representation.
  • FIG. 1 illustrates adaptive bit modification for successive data samples in successive data frames in accordance with the present invention.
  • Samples of digital data are selectively scrambled such that some of the Most Significant Bits (MSBs) are preserved, and some or all of the remaining data bits (e.g., LSBs) are scrambled.
  • MSBs Most Significant Bits
  • LSBs remaining data bits
  • the key to unscramble the data can be concealed into the scrambled signal (e.g., using the techniques discussed in the aforementioned patents and applications) so that the key is no longer decodable once the content data is unscrambled.
  • the horizontal axis designates successive frames and samples of digital data.
  • each frame has fifteen samples, and each sample has twenty-four bits, although the present invention can accommodate any variation of these parameters .
  • Each sample has a dynamic range between zero to twenty-four bits which is defined by the most significant non-zero bit, not including a sign bit, which may be the leftmost bit in each sample. 11
  • An original waveform 110 designates the dynamic range of each sample prior to scrambling in accordance with the present invention.
  • Regions 120 and 125 designate the bits in each sample which are not modified, while a region 130 designates the bits in each sample which may be scrambled in accordance with the present invention.
  • the first sample 115 of FRAME A has a dynamic range of 18 bits .
  • An example of such a sample might be:
  • the specific number of bits which are not modified can be selected by experimentation to yield data with a desired level of degradation.
  • the bits in the region 130 are subject to scrambling as discussed in greater detail below.
  • the selectively scrambled samples appear noisy.
  • audio samples will sound noisy to the listener, e.g., when played on a player in the user's home.
  • the samples will sound noisier for samples where fewer MSBs are preserved, although the perception of the noise can vary based on the dynamic range of the each sample as well as the neighboring samples, the type of audio being played, the listening environment and other factors .
  • the noise is generally not objectionable for player functions such as cueing and fast forward playback.
  • fast forward playback or fast reverse, if provided
  • there is insufficient time for the player to descramble the samples During normal playback, the player has sufficient time to descramble the samples, so the content is heard or seen with its full dynamic range.
  • the selectively scrambled content material limits the amplitude of the scrambled waveform such that it does not exceed the dynamic range of the original waveform.
  • the scrambled content does not damage the video or audio equipment even if it is played through any video or audio playback system.
  • Scrambling of the data bits can be done within each sample (intra-sample scrambling) or within a group of samples (inter-sample scrambling) . Furthermore, a combination of intra-sample and inter-sample scrambling can be used.
  • Scrambling may take the form of interchanging the position of the data bits (inter-sample scrambling) , masking the data bits with a sequence derived from the scramble key or parts of a scramble key (intra-sample scrambling) , or combinations thereof.
  • the purpose is to randomize or whiten the statistics of the scrambled data bits to make it
  • the descrambler must undo this mapping of the bits .
  • Random or pseudo-random scrambling improves the security of the scrambled data since it will be more difficult for an attacker to detect patterns in the scrambled data.
  • FIG. 2(a) illustrates intra-sample scrambling in accordance with the present invention.
  • An original sample 200 includes bits 31 7 31 6 31 5 31 4 81 3 31 2 81,51 0 , where "SI" denotes "sample
  • FIG. 2(b) illustrates original, unscrambled samples. Like-numbered elements correspond to one another in the figures.
  • FIG. 2(c) illustrates the samples of FIG. 2(b) after horizontal, inter-sample scrambling in accordance with the present invention.
  • Samples 1 (200'), 2 (260') and 3 (270') correspond to Samples 1 (200), 2 (260) and 3 (270) , respectively.
  • the waveform samples are grouped into frames.
  • Each frame is associated with a scramble key, such as a pseudorandom key.
  • the scramble key can be different for each frame and is determined at encoding time.
  • a particularly useful case of inter-sample scrambling is horizontal scrambling, where the bits with the same weight are interchanged among the samples .
  • bit Sl 0 replaces bit S3 0
  • bit SI replaces bit S3 ⁇
  • bit Sl 2 replaces bit S2 2 , and so forth.
  • FIG. 3 illustrates a data scrambler and scramble key encoder in accordance with the present invention.
  • the scramble key is embedded into a scrambled audio content .
  • the scrambler/encoder 300 includes a scramble key generator 310 for generating a scramble key.
  • the scramble key does not have to be the same length as the sample length. A longer scramble key length makes the data more secure.
  • the scramble key is provided to a key buffer
  • the scramble key is provided to a scrambler for scrambling the samples in the original waveform, e.g., as discussed in connection with FIGs 2 (a) -(c) .
  • the same scramble key may be used to scramble a number of samples in a frame.
  • the scrambled waveform is provided to a scramble key encoder 340 to encode the scramble key into the waveform, thereby providing the scrambled waveform with the embedded scramble key.
  • the scramble key may be encoded as auxiliary data in the waveform using the techniques discussed in the aforementioned U.S. patents and applications.
  • the scramble key is concealed by the noise-like scrambled content .
  • FIG. 4 illustrates a data descrambler and scramble key decoder in accordance with the present invention.
  • a descrambler/decoder 400 includes a scramble key decoder 410 that receives the scrambled waveform, e.g., from the scrambler/encoder 300 of FIG. 3.
  • the scrambled waveform may be communicated via any communication channel, and/or recovered from a storage medium, for example.
  • the scramble key decoder 410 recovers the scramble key that was used to scramble the following frame and stores it in a key buffer 420.
  • the scramble key decoder 410 operates using the corresponding technique used by the scramble key encoder 340.
  • the scramble key is retrieved from the buffer 420 for use by a descrambler 430 in descrambling the current frame of samples to provide the descrambled waveform.
  • the descrambled waveform may undergo subsequent processing, such as digital-to-analog conversion, e.g., for viewing or listening by a user.
  • the scramble key is no longer recoverable even by an attacker who has the scramble key decoder 410 17
  • the scramble key is scrambled by the descrambler 430.
  • FIG. 5 illustrates a detailed data scrambler in accordance with the present invention.
  • successive samples each having W bits (sample width)
  • W bits sample width
  • Non-scrambled buffered samples are output from the sample frame buffer 510 according to a linear address generator 515 for scrambling at a scrambler 330 according to a scrambling key.
  • Buffered samples in a pseudo-random order within a frame are output from the sample frame buffer 510' according to addresses from a scramble address generator 525, which receives the scramble key.
  • the buffered samples are bit-wise ANDed at an AND function 530 with a mask bit string for the LSBs (LSB_MASK) to produce LSBs that are interchanged with other samples within the current frame.
  • LSB_MASK is a bit string with l's corresponding to the LSBs to be scrambled in the buffered samples, and O's for the other bits in the buffered samples.
  • a range detector and mask generator function 535 provides LSB_MASK, along with a mask bit string for the MSBs which are to be preserved (i.e., not scrambled) , MSB_MASK.
  • MSB_MASK is a bit string with 1 ' s corresponding to the MSBs to be preserved in the buffered samples, and O's for the other bits in the buffered samples . 18
  • MSB_MASK is bit-wise ANDed with the buffered samples from the sample frame buffer 510 at an AND function 540 to produce the preserved MSBs.
  • Scrambled samples from the scrambler 330 are bit wise ANDed at an AND function 545 with MSB_MASK/ (the inverse of MSB_MASK) and LSB_MASK/ (the inverse of LSB_MASK) .
  • MSB_MASK/ and LSB_MASK/ are obtained from the inverters 550 and 555, respectively.
  • the output of the AND function 545 comprising the scrambled middle bits is provided to a bit-wise OR function 560 for combining with the preserved MSBs and the LSBs that are interchanged with other samples in a frame.
  • the output of the OR function 560 comprises the scrambled samples, which may be provided to the scramble key encoder 340 to provide scrambled samples with the embedded scrambling key.
  • the samples are now ready, e.g., for transmission across a network, or storage on a storage medium.
  • the scrambled key may be embedded in the scrambled samples by providing a scramble key encoder (such as element 340 in FIG. 3) . Note that the embedding of the scrambling key is optional.
  • one method to selectively scramble the audio is to preserve the sign bit and, e.g., two most significant bits of each sample.
  • Amplitude range detection is performed on each audio sample. A mask is generated for each sample corresponding to the amplitude range of that 19
  • MSB_MASK Hexadecimal
  • Each sample has sixteen bits, where the leftmost bit is a sign bit. For example, for the sample value, 0xff98 in hexadecimal, or 1111111110011000 in binary, bitl ⁇ ("1") indicates that this is a negative number, i.e., negative 0x61, or -97 in decimal. Thus, the dynamic range is seven bits (bitO to bit ⁇ ) .
  • the remaining bits are separated into two groups - the least significant bit, and all other remaining bits.
  • the least significant bit is scrambled horizontally by exchanging positions within a frame. Inter-frame scrambling may also be used.
  • the other remaining bits are scrambled by XORing with a bit pattern which is generated from all or part of the scramble key.
  • a linear shift register can be used to vary the bit pattern for each sample. 20
  • the scrambled output consists of 1) the preserved MSBs, 2) the intra- sample scrambled middle bits, and 3) the horizontal inter-sample scrambled LSBs.
  • FIG. 6 illustrates a detailed data descrambler
  • the descrambler may be used for processing data received from the scrambler 500, for example.
  • Elements 610, 510' ', 515', 530' 535', 540', 545', 550', 555' and 560' correspond to elements 510, 510', 515, 530, 535, 540, 545, 550, 555 and 560, respectively in FIG. 5.
  • the scramble key is decoded from the scrambled samples at the scramble key decoder 410, and provided to a buffer 420, and then to the descrambler 430.
  • a linear address generator 515' is used, if necessary, for providing an address to a sample frame buffer 610 to restore the bit pattern for each received sample.
  • the received, scrambled samples are provided from the sample frame buffer 610 to the range detect/mask generator function 535'.
  • the preserved MSBs in each sample are identified the same way as at the scrambler, by using amplitude range detection.
  • the descrambled middle bits in each sample are combined at the OR function 560' with the preserved MSBs and the reordered LSBs .
  • the inverse MSB mask (MSB_MASK/) is provided at the output of an inverter 550' to an AND function 545' for ANDing with the descrambled samples.
  • the output of the AND function 545 ' is provided to the 21
  • OR function 560' for ORing with the preserved MSBs and the reordered LSBs within a frame.
  • the reordered LSBs within a frame are derived from ORing LSB_MASK with the reordered buffered samples, which are derived from the sample frame buffer 510'' in response to addresses from a descramble address generator 625.
  • the LSB's position in a frame is restored, and the descrambled output is obtained by combining the three components at the OR 560' .
  • FIG. 7 illustrates adaptive bit modification with a fixed minimum dynamic range for successive data samples in successive data frames in accordance with the present invention.
  • the preserved dynamic range of the MSBs can be fixed, e.g., at 16 bits.
  • N the number of MSBs to be preserved, can be fixed as a preset parameter before processing (N may vary from 0 to the full dynamic range of the digitized samples) .
  • N 8 in the example shown.
  • the original waveform 110 indicates the dynamic range of each sample prior to scrambling.
  • Region 720 designates the bits in each sample which are not modified, while a region 730 designates the bits in each sample which may be scrambled. For example, for FRAME A, bitl5 (corresponding to a dynamic range of 16) and higher in each sample are not modified, while bitO through bit 14 are modified. For FRAME B and FRAME C, all of the bits are modified, e.g., up to the dynamic range of each sample. 22
  • An advantage of this scheme is that there is no need to determine the dynamic range of each sample at the encoder and decoder.
  • the invention may be implemented with various other alternatives and enhancements, as follows.
  • the number of MSBs to be preserved (N) can be dynamic, varying from frame to frame.
  • scrambling can be done across video frames.
  • Amplitude range detect and mask generation can be a look-up-table with heuristic rules.
  • Scrambling frames can vary in length.
  • Horizontal scrambling can be done on any number of LSBs .
  • All or part of the scramble key can be hidden in the same frame, the previous frame, or any other frame of the content .
  • the implementation hinges on the amount of buffer memory available and the throughput delay requirement .
  • the key can be hidden electronically within sector data or physically with the use of techniques such as pit width modulation.
  • All or part of the scramble key for one stream of the content can be hidden in any separated media such as a pre-paid card.
  • the key may also be a product of a transaction authorization via telephone, Internet, or any other communication means .
  • Scrambling can be done between two or more channels of the same data stream (e.g., front left and right channels of a multi-channel audio segment) .
  • Scrambling can be selectively done for selected channels of a multi-channel stream (e.g., front left and front right channels are scrambled but center, rear left, rear right and subwoofer channels are not) .
  • Scramble Keys can be generated with either non-linear shift registers or non-linear feedback shift registers.
  • side information coded in the compressed stream can simplify the range detection process.
  • bit allocation information For contents in a compressed form, side information coded in the compressed stream, such as bit allocation information, can simplify the range detection process.
  • bit allocation information For some frequency 24
  • the modified frequency samples must be re-packaged to conform to the original bit stream format . This in most cases should not require re-quantization, just re- packetization. This process will be specific to the compression technique used. Some compression schemes may require variable length encoding, such as Huffman code, and specific measures must be taken if the size of the compressed bit stream must remain unchanged. Most compression schemes inherently produce variable length bit streams, and the subsequent transport stream format usually accommodates the change in the size of the bit stream.
  • One side benefit of applying the partial scrambling technique of the present invention to the compressed bit stream may be a slightly easier self synchronization at the decoder. This may occur since the frame structure or the packet structure present in the compressed bit stream format can make it easier for the decoder to determine the scrambling frame boundary.
  • the present invention provides a system for scrambling digital samples of multimedia data, including audio and 25
  • the quality level may be associated with a particular signal to noise ratio, or quality level that is determined by objective and/or subjective tests, for example.
  • a number of LSBs can be scrambled in successive samples in successive frames.
  • the parameters for scrambling may change from frame to frame.
  • the scrambling key can be embedded in the scrambled data and recovered at a decoder to descramble the scrambled samples. After descrambling, the scramble key is no longer recoverable because the scramble key is scrambled by the descrambler.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Computer Security & Cryptography (AREA)
  • Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
  • Signal Processing For Digital Recording And Reproducing (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)

Abstract

L'invention concerne un système (300, 500) permettant de brouiller des échantillons numériques (115, 200, 250, 260, 270) de données multimédia, notamment des échantillons de données audio et vidéo, de sorte que le contenu desdits échantillons se dégrade mais reste reconnaissable, ou se présente à un niveau de qualité souhaité. Les échantillons peuvent se présenter sous n'importe quel format numérique comprimé ou non, y compris les échantillons à modulation par codage d'impulsions (PCM), les échantillons en représentation en virgule flottante, les échantillons de programme de compression-extension (par exemple ν-law et A-law), et d'autres trains binaires comprimés. Le niveau de qualité peut être associé, avec un signal particulier, à un certain rapport signal/bruit, ou être défini par des contrôles objectifs et/ou subjectifs, par exemple. Plusieurs bits de plus faible poids (LSB) peuvent être brouillés dans des trames successives (TRAME A, TRAME B, TRAME C), les paramètres de brouillage pouvant changer de trame à trame. La clé de brouillage (310) est par ailleurs entièrement ou partiellement incorporée (340) aux données brouillées, puis récupérée au niveau d'un décodeur (400, 600) destiné à être utilisé pour le désembrouillage. Après ce désembrouillage, la clé de brouillage ne peut plus être récupérée, étant elle-même brouillée par le désembrouilleur.
EP99919913A 1998-04-21 1999-04-20 Systeme de brouillage multimedia adaptatif (mass) Withdrawn EP1095517A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US8248898P 1998-04-21 1998-04-21
US82488P 1998-04-21
PCT/US1999/008635 WO1999055089A1 (fr) 1998-04-21 1999-04-20 Systeme de brouillage multimedia adaptatif (mass)

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EP1095517A1 true EP1095517A1 (fr) 2001-05-02

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EP99919913A Withdrawn EP1095517A1 (fr) 1998-04-21 1999-04-20 Systeme de brouillage multimedia adaptatif (mass)

Country Status (8)

Country Link
EP (1) EP1095517A1 (fr)
JP (1) JP2002512494A (fr)
KR (1) KR20010034802A (fr)
CN (1) CN1151673C (fr)
AU (1) AU3752599A (fr)
CA (1) CA2329315A1 (fr)
MX (1) MXPA00010337A (fr)
WO (1) WO1999055089A1 (fr)

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Also Published As

Publication number Publication date
JP2002512494A (ja) 2002-04-23
AU3752599A (en) 1999-11-08
CA2329315A1 (fr) 1999-10-28
CN1151673C (zh) 2004-05-26
MXPA00010337A (es) 2003-05-19
WO1999055089A1 (fr) 1999-10-28
CN1301460A (zh) 2001-06-27
KR20010034802A (ko) 2001-04-25

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