KR20020006693A - Protecting content from illicit reproduction by proof of existence of a complete data set - Google Patents

Abstract

Multiple data items are selected for inclusion within the data set, discouraging the transmission of the entire set over a limited bandwidth communication path such as the Internet. Each portion of the data set is connected to the entire data set so that portions of independently distributed data sets can be distinguished. For example, in the case of an audio recording, the data set includes the entire album, and individual songs on the album make up portions of the data set. By linking each song to an album, a compatible player can be configured to refuse to play items in the absence of a complete data set. Accordingly, the theft of the song requires theft of the entire album. Uncompressed digital recordings of the entire album consume hundreds of megabytes of data, and the unrealization or impracticality of downloading hundreds of megabytes of data would provide sufficient abandonment for the theft of uncompressed content material. It is predicted. In a preferred embodiment, a watermark containing a "globality parameter" associated with the data set is generated for each session of transmitted data. The globality parameter corresponds to a hash value based on a random number stored inside the watermarks of each section. When provided for performance, the totality parameter is read and the watermarks of random selection of sections within the data set are compared with this totality parameter, with statistical certainty, to ensure that the entire data set exists. .

Description

PROTECTING CONTENT FROM ILLICIT REPRODUCTION BY PROOF OF EXISTENCE OF A COMPLETE DATA SET}

The present invention relates primarily to the field of civilian electronic devices, and more particularly to the protection of copy-protected content material.

Illegal distribution of copyrighted material deprives the copyright holder of the legally protected legal fees for this material, and provides the benefit of such illegally distributed material providers to promote continuous illegal distribution. In view of the ease of information transfer provided by the Internet, content materials intended to be protected from copying, such as art expressions or other materials with limited distribution rights, are subject to opposing illegal distribution. The MP3 format for storing and delivering compressed audio files enables mass distribution of audio recordings, since digital audio recordings of 30 or 40 megabytes of song can be compressed into 3 or 4 megabytes of MP3 files. It was. Using conventional 56 kbps dial-up with the Internet, such MP3 files can be downloaded to the user's computer in minutes. Thus, the malicious person reads the songs from the original legal CD, encodes these songs in MP3 format, and places these MP3 encoded songs on the Internet for opposing illegal distribution. Alternatively, a malicious user may provide a direct dial-in service for downloading self MP3 encoded songs. The illegal copy of the MP3 encoded song can then be played by a software or hardware device, or decompressed and stored on a recordable CD for playback on a conventional CD player.

A number of measures have been proposed to limit the reproduction of copy-protected content material. The Digital Music Copyright Protection Group, Secure Digital Music Initiative (SDMI), and others encourage the use of "digital watermarks" to identify authorized content. European patent application EP 0981901 "Embedding auxiliary data in a signal" discloses a technique for embedding a watermark in an electronic material and is incorporated herein by reference. As with document watermarks, digital watermarks are inserted detectably but invisibly within the content material. For example, audio reproduction of a digital music recording including a watermark is indistinguishable from reproduction of the same recording having no watermark. However, the watermark detection apparatus can identify these two recordings based on the presence or absence of the watermark. Since some content material cannot be copy protected and cannot contain a watermark, the absence of a watermark cannot be used to distinguish between legal and illegal material. Rather, the absence of a watermark indicates that it is content material that can be legally copied freely.

Other copy protection schemes may be used. For example, the European patent application EP0906700 "Method and system for transferring content information and supplemental information related" is protected by copyright through the use of a watermark "ticket" which controls the number of times protected material can be played. A description of the protection of the material is presented and incorporated herein by reference.

Accurate reproduction of the watermarked material allows the watermark to be reproduced in a copy of the watermarked material. However, inaccurate, i.e., lossy reproduction of the watermarked material does not provide for the reproduction of the watermark in the lost copy of the material. Many protection schemes, including those of the SDMI, have used this lossy recovery feature to distinguish legitimate data from illegal data based on the presence or absence of the corresponding watermark. In the SDMI system, two types of watermarks are defined, namely "robust" watermarks and "fragile" watermarks. Robust watermarks correspond to watermarks that are expected to withstand lossy reproduction designed to maintain a substantial portion of the original content material, such as MP3 encoding of audio recordings. In other words, if the reproduction holds enough information to allow proper performance of the original recording, a robust watermark is also maintained. In contrast, a soft watermark corresponds to a watermark that is predicted to be obsolete by lossy reproduction or other illegal changes.

In the SDMI system, the presence of a robust watermark indicates that the content material is copy-protected, and the absence or tampering with the corresponding soft watermark when there is a robust watermark indicates that the copy-protected material has been tampered with in some way. Indicates. SDMI compliant devices may use a tampered watermark except that tampering or absence of the watermark is justified by an "SDMI-certified" process, such as SDMI compression of copy-protected material for use in a portable player. Or a watermark having a strong watermark is detected but the watermark having no soft watermark is configured to refuse to play the inserted material. For ease of reference and understanding, the term "rendering" is used herein to include the processing or delivery of content material such as playback, recording, conversion, authorization, storage, loading, and the like. Such a system serves to limit the distribution of content material through MP3 or other compression techniques, but does not affect the distribution of counterfeit unaltered (uncompressed) copies of the content material. Such limited protection is believed to be commercially viable, as the cost and inconvenience of downloading a very large file to obtain a song tends to abandon theft of uncompressed content material.

Finally, it is an object of the present invention to extend the protection of copy protected material to include protection of compressed content material.

The above and other objects are achieved by selecting a sufficient number of data items to be included within the data set, giving up the transmission of the entire set over a limited bandwidth communication path such as the Internet. Since each portion of the data set is connected to the entire data set, portions of these data sets that can be distributed independently can be distinguished. For example, in the case of an audio recording, the data set includes the entire album, and the individual songs on this album constitute portions of this data set. By linking each song to the album, the compatible player can be configured to refuse to play these items in the absence of a complete data set. Accordingly, the theft of the song requires theft of the entire album. Uncompressed digital recordings of the entire album occupy hundreds of megabytes of data, and the inadequacy or unreality of downloading these hundreds of megabytes of data would be enough to discourage the theft of uncompressed content material. do. In a preferred embodiment, one watermark is generated for each section of the transmitted data set that includes the "entirety parameter associated with the data set. The overall parameter is the watermark of each section. Corresponds to a hash value based on a random number memorized in. When provided for performance, the globality parameter is read and compared to this globality parameter with watermarks of a random selection of sections within the data set, Using statistical certainty, confirm that the entirety of the data set exists.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings in which:

1 shows an example of a system for protecting copy protected content material in accordance with the present invention;

2 illustrates an example of a data structure that facilitates determining the presence of an entirety of a data set in accordance with the present invention.

3 shows an example of a flow diagram of an encoder for generating a data set and accompanying parameters to facilitate determining the presence of an entirety of a data set in accordance with the present invention;

4 shows an example of a flow diagram of a decoder for playing a data item of a data set in dependence upon the presence of the entire data set in accordance with the present invention.

Throughout the drawings, the same reference numerals indicate similar or corresponding features or functions.

Theft of items may be abandoned by making them more time consuming or more inconvenient than the value of stolen items. For example, bolted safes are often used to protect small valuables because the effort required to steal the safes generally exceeds the benefits that can be expected by stealing the safes.

The time required to download the average song's MP3 encoding output from the Internet using a 56 kbs modem is about 15 minutes, depending on network load and other factors. While it may not be possible to define a particular "value" for the duration of a download, it is believed that millions of people are willing to invest 15 minutes of download time to receive songs on the Internet. In contrast, the time required to download the average uncompressed digital record of an average song using a 56 kbps modem is about two hours, and few people would spend two hours of download time to download songs from the Internet. . Although a person can sometimes invest two hours of download time to receive a song, the possibility of two hours of downloads, which is a common means of stealing songs, is expected to be minimal. For this reason, conventional protection schemes have been based on the need to identify compressed copies of protected material using, for example, the combination of robust watermarks and soft watermarks described above.

For ease of reference and understanding, the terms "lossless" and "uncompressed" are used synonymously herein. As will be apparent to those skilled in the art to which the present invention pertains, the present invention is independent of whether the transmitted information is compressed or uncompressed, and whether the compression is lossy or lossless. Conventional solutions exist for the detection of lossy encoding results, such as MP3, and since the degree of compression achieved by lossy compression of MP3 enables mass distribution of protected material, the term "compressed" is used herein. And "uncompressed" are used. As is known in the art, there is a lossless compression scheme. However, a lossless compression scheme does not achieve the reduction of data that lossy compression achieves and is not considered "compressed" enough to be distinguished from "uncompressed" for the understanding of the present invention.

Also, for ease of understanding, the present invention is presented herein with the background of digitally recorded songs downloadable from the Internet. As will be apparent to those skilled in the art to which the present invention pertains, the present invention is applicable to any recorded information expected to be transmitted over a limited bandwidth communication path. For example, individual content material items may be data records that are inside a larger database, rather than songs in an album.

The likelihood of a person downloading a song illegally can be thought of as being inversely proportional to the time required to achieve the download. The present invention is based on the assumption that there are some threshold download durations that are expected to allow for the expected loss of revenue due to illegal downloads. Multiple experiments and investigations can be performed to determine the download duration sufficient to discourage the illegal download of one song, i.e., such a duration of discouraging-duration can be estimated, 1/2 to 1 It seems to have a magnitude of time. That is, if the duration is less than half an hour, there are many "illegal" illegal downloads of the popular song, and if the duration is greater than one hour, even if the song is very popular, there is no "almost" illegal download. It seems.

As technology advances, and as other communication schemes become available, the time required to download uncompressed files can be expected to decrease. For example, using DSL or cable connections to the Internet reduces the time required to transmit uncompressed digital songs to less than five seconds, depending on network load and other factors. As mentioned above, recent protection schemes cannot distinguish a lossless copy of digital data from an original. Thus, in a high speed data transfer environment, the potential for loss of revenue due to illegal download of uncompressed digital songs is expected to increase significantly.

According to the invention, individual songs on a compact disc (CD) or other medium are connected to the entire contents of the CD, and the compatible playback or recording device is configured to refuse to play the individual songs in the absence of the full contents of the CD. . Even at DSL and cable modem speeds, the time required to download an entire album on one CD in uncompressed form is expected to be greater than one hour, depending on network load and other factors. Thus, by requiring the entire content of the CD to be present at a download "cost" of more than one hour, the likelihood of theft of songs through opposing distribution on the Internet is significantly reduced.

1 shows an exemplary block diagram of a protection system 100 in accordance with the present invention. The protection system 100 includes an encoder 110 for encoding the content material on the recording medium 130 and a decoder 120 for playing the content material from the recording medium 130. The encoder 110 includes a selector 112 for selecting content material from a source, and a recorder 114 for recording the material on the recording medium 130. The selector 112 may be configured to select, for example, content information corresponding to songs accumulated in the album. The recorder 114 properly formats, encodes, and stores the information on the recording medium 130 using techniques known in the art.

According to the present invention, the encoder 110 connects each item selected by the selector 112 with the entirety of the information recorded on the record carrier 130 by the recorder 114. It is provided. Generally speaking, the information stored on the record carrier 130 constitutes a plurality of data items, the entirety of the information stored on the record carrier 130 constitutes a data set, and each data item is linked to the data set.

Decoder 120 according to the present invention includes a renderer 122 and a gate 124 controlled by the integrity checker 126. The renderer 122 retrieves information from a recording medium reading apparatus such as the CD reader 132. As is known in the art, renderer 122 retrieves information by specifying a location index, and in response, reader 132 provides the data disposed at a designated location index on record carrier 130. Block reading of data at adjacent locations on the record carrier 130 is accomplished by specifying a location index and a block size.

The dashed line shown in FIG. 1 shows an example song extractor that extracts a song from the record carrier 130 and sends it to an example CD imitator 144 that indicates a possible illegal download of the song over the Internet. 142 is shown. CD emulator 144 represents a software program that provides information in response to, for example, a conventional CD-reading name. Alternatively, the information received from the song extractor may be recorded on a CD record carrier and provided to a conventional CD reader 132. As discussed above, the song extractor 142 is likely to be used, since it has been assumed that the entire transfer of the content of the record carrier 130 is abandoned due to the content of the record carrier 130 having a deliberately large size.

In accordance with the present invention, the integrity checker 126 is typically configured to obtain data from the record carrier 130 via the renderer 122 to determine whether the entire data set is present. Any number of various techniques known in the art can be used to confirm the presence of the entire data set. For example, by calculating a checksum on the data items available at renderer 112 and comparing this checksum with the checksum corresponding to the original full data set, the data to verify that all data items exist. Checksums corresponding to data terms within the set may be used. Such checksums can be digitally signed and communicated with the data set and then verified using an encryption key.

In a civilian environment, such as an audio CD player, a checksum based approach cannot be used. Audio CD players include error correction and other decoding schemes that allow variation with every read of the CD. An audio CD, for example, does not necessarily start playing a song at exactly the same point. Likewise, if an error is detected when the CD is being read, the repetition of the previous session is often replaced instead of the section with the error. Fluctuations of a few bytes at the beginning of a song, or repetition of bytes up to several seconds, do not result in noticeable differences, but the presence or absence of these bytes has a significant effect on the checksum associated with the song.

The watermark and its corresponding watermark detection apparatus are configured to provide accurate and repeatable reading of the watermark under various circumstances. For example, watermarks are generally recorded at a bit rate significantly lower than the bit rate of the recorded audio signal, and redundant recording of the watermark is used to further improve the likelihood that the correct value is read as a watermark. As described above, in general, by changing the bit rate and redundancy of the recording of the watermark, the robustness of the watermark can be changed. "Smooth" watermarks are also generally constructed to withstand small variations and deviations that are common when reading information from a conventional civil CD player. As used herein, the term watermark includes one or more watermark encoding outputs, and the watermark may include, for example, soft and robust components. Depending on the watermark generation method, these components can be inserted inside a section independently or as a common entity. For ease of understanding, the term watermark, soft watermark, and robust watermark are used herein regardless of how individual components are collected or separated during the watermark generation process.

2 illustrates an example data structure 200 that stores data items within a data set and facilitates checking whether a full original data set exists. The track 210 and section 220 structures are shown in accordance with the memory structures of conventional CD and other storage media. In a preferred embodiment, the data set is self-referential and the data set includes one or more parameters that can be used to confirm the presence of other components of the data set. In the example data structure 200, a random number R (i) 234 is assigned to each section 220 of the data set. The hash H (R (i)) of each of these random numbers R (i) is preferably stored on the record carrier as " out of band " data (OBD) 240. For example, such data 240 is a "CD-ROM data" inside a composite audio-data CD, a separate unique data section, a fake song containing only data, and the like. Can be stored internally. A hash of one of the complexes H (H (R 0), H (R 1),…, H (Rn)) 240 of hashes is used as the check value CHK to confirm the integrity of the data set. Check value CHK 232 and random number R (i) 234 form a watermark 230 associated with each section 220 of the data set. That is, in the preferred embodiment, the CD 130 of FIG. 1 has a watermark 230 that includes an identifier CHK 232 of the entire data set on the CD and an identification random number 234 of the section 220. Each recorded section 220 is formed. In general, hash values are used because hash operations are irreversible. The value used to generate the hash value cannot be determined, nor can the effect of a change of one or more items used to form the hash value be determined (in this context, the term "undeterminable" in a cryptographic sense). The determination of this value can be expected to consume more time and resources than practically tracking.) Section watermarks can be robust or soft watermarks. In the preferred embodiment, to ensure the identification of the material as protected material, the check value CHK 232 is encoded as a robust watermark, and the random number R (i) 234 is encoded as a soft watermark. As mentioned above, robust watermarks are recorded at lower bit rates or with more redundancy than softer watermarks. In other words, a soft watermark consumes less resources than a robust watermark. In addition, as discussed above, a soft watermark provides an indication of other forms of tampering, such as compression of protected data. The check value may be part of a hash of the complex, such as the lower m bits. Although the security of partial hash values is smaller than that of complete hash values, the saving of resources to store these values can justify this reduction in security.

3 shows an exemplary flow diagram for an encoder 110 for generating a data set on a medium in accordance with the present invention. At 320, a data item is selected for inclusion in the data set. This data item may be a song selected for inclusion in the album, a data recorder selected for inclusion in the database, or the like. A data item contains one or more data sections. For example, one song may be divided into a plurality of identical time duration portions, and each data record may form one section. At 320, a random number R (i) is assigned to each section of the data item, and at 330 the size of the data item is added to the accumulated size of the entire data set. According to the present invention, a plurality of data items are added to the data set until the size of the data set is considered large enough to abandon the transmission of subsequent data sets over a limited bandwidth communication channel. This "discouraging size" is a subjective value, depending on the assumed usable communication bandwidth, losses incurred by transmission, and the like. If the determination size is not reached, then at 335, another data item is selected for inclusion within the data set via branch back to block 310. Although not shown in the example flow diagram of FIG. 3, other criteria may be used to determine whether to add additional data items to the data set. For example, if the data items match the songs of the current album collection, all songs are generally added to the data set, regardless of whether the size of the data set exceeds the determined disclaimer size. If all songs in the album collection have been selected and have not yet reached the discretionary size criterion, other data items are selected to accumulate the required discretionary size. For example, data items containing random data bits may be added to the data set to increase its size. These random bits are generally stored as out-of-band data, CD-ROM data, and the like, in order to prevent them from being played as an audible sound by a conventional CD player. Alternatively, data items may include other sample songs that are provided to facilitate the sale of other albums, or picture and video sections associated with the recorded content material. Similarly, the recorded information on the recorded recording medium may include promotional material such as an internet access subscription program. These and other means of adding size to a data set are apparent to those skilled in the art in light of the present invention. In accordance with the present invention, each of the selected data items is coupled to the data set such that the removal or alteration of any data items, including random sections, promotional materials, etc., that have been added to increase the size of the data set, is such a data set. It can be used to exclude subsequent playing of data items from.

After the data items are selected to provide a data set with sufficient size, at 340, a check value CHK is calculated based on the complex of random numbers that have been assigned to the sections of each data item. Such a complex may include, for example, a checksum corresponding to a random number, a checksum corresponding to a function such as a hash function of each random number, and the like. As mentioned above, such a CHK value may preferably be a hash of a complex of random numbers or part of such a hash. At 350, a watermark is generated for each section of the data set that also includes such a CHK value and a random number R (i) assigned to the section. As mentioned above, the CHK value is preferably encoded as a robust watermark and the random number is encoded as a soft watermark. At 360, each section is recorded on the record carrier with such a composite watermark, and a hash of random numbers in each section is stored at 370, preferably on the record carrier as out-of-band data (OBD). Accordingly, individual data items are linked to the entire data set, and the validity of such a full value can be confirmed through the self-referential hash function of the random number that was used to generate the CHK value. Other encoding schemes for linking individual data items to a data set will be apparent to those of ordinary skill in the art in view of this specification.

4 is dependent on the presence of the entirety of the data set associated with the data item. A flow diagram of a decoder 120 configured to play a selected data item, such as a selected song, is shown. This flow diagram assumes that the encoding method of FIG. 3 was used to create the original of the data item and data set. If other connection schemes are used, those skilled in the art can appropriately modify the example flow diagram shown in FIG. 4 in light of the present embodiment. The flow diagram shown in FIG. 4 is assumed to be activated when determining that the selected data item is a copy protected item, for example, via a copy protection watermark or other identification mechanism. At 410, a hash value of a random number associated with each section of the data items in the data set is read from the record carrier, such a read being from a genuine copy of the recorded content material (130 in FIG. 1) or from an illegal source ( Read from 144 in FIG. At 420, hashes are calculated based on the complexes of these hash values using the same algorithm as used at 340 in FIG. 3 to generate CHK values that are contained within the watermark of each section of the true copy of the content material. At 430, a random section of the data set is selected, and at 440 the check value of the watermark is read as CHK '. Alternatively, to immediately confirm whether the selected data item is part of the original data set, the first section selected for confirmation may be a section from within the data item selected for performance. In terms of recorded songs, the data section generally corresponds to the 15 second sections of the song. If at 445 the calculated check value CHK is not equal to the read check value CHK ', this indicates a modification to the collection of hashes of random numbers, so that at 480 the decoder refuses to play the content material.

To confirm that the data section is hardly modified, the random number assigned to the randomly selected section Sx at 450 is read as R '(x). As mentioned above, the random number is preferably stored as a soft watermark, and a feature of the soft watermark is that significant modifications to the data containing the watermark result in the modulation or destruction of the soft watermark. The hash H (R '(x)) of the random number read at 450 is similarly calculated, and this hash H (R' (x)) is compared with the corresponding hash value H '(R (x)) that was read at block 410. Is then used to generate the confirmation check value CHK. If these hash values do not match at 455, the decoder is configured to refuse to play the content material at 480. If these hash values do not match, other sections are similarly examined through loops 465-430 until sufficient confirmation is obtained that the content material is hardly modified from the true copy. In a preferred embodiment, only one or two sections are tested to minimize the delay introduced by this data-set-completeness check procedure. If enough confidence is obtained at 465 that the entire data set is present, the song selected at 470 is played. As will be apparent to those skilled in the art, additional confirmation tests may be applied later. Preferably, when each section of the song is read, the watermark of each section of the selected song is checked to check whether each CHK 'value contained in each section corresponds to the confirmation check value CHK, Verify that each section of is a valid component of the original data set.

The foregoing is merely illustrative of the principles of the present invention. Thus, it will be apparent to one skilled in the art that the present invention may be embodied in various configurations that fall within the spirit and scope of the present invention, although not explicitly described or illustrated herein. . For example, the embodiments given above illustrate each part of the recorded data that is part of the data set. In yet another embodiment, selected data items or selected portions of data items may be used to form a data set, to achieve an object related to efficiency. For example, because the watermark process may be based on a fixed block size for each watermark or for each duplicate copy of the watermark, the end of the song may be defined by the "data set" defined herein. It may not be part of it. For example, if a watermark or other parameter requires 10 seconds of recording for secure insertion, the rest of (song length) modulo (10 seconds) is recorded on the recording medium, but is examined and It is not included inside a "data set" that has a completeness. Similarly, some promotional material may be included on the recorded record carrier, but may be deliberately excluded from the data set so that it can be freely reproduced and played in other cases. Also, note that the example flow diagrams are presented for ease of understanding, and that particular arrangements and sequences are given for illustration. For example, although a simple equation is shown inside the decision blocks to determine if it matches, depending on the particular technique used to encode or decode the parameters, the evaluation of whether the read item matches the determined item is a variety of intermediate processes. It may include. To determine whether two values are "close enough" to imply a match, these procedures may include, for example, decryption, fuzzy logic, or statistical testing based on a particular key. Modifications such as these and other variations are apparent to those skilled in the art in light of the present invention and are included within the spirit and scope of the appended claims.

Claims (50)

In a way to discourage theft of content material, Collecting a plurality of data items 210 including content material to form a data set having a size 335 large enough to abandon the transmission of subsequent data sets over a limited bandwidth communication channel ( 310-335), Combining each data item of the plurality of data items 210 into a data set to facilitate prohibition of processing of each data item in the absence of a full data set (350-360); Characterized in that the method. The method of claim 1, Combining the plurality of data items 210, Generating (350) one or more watermarks (230) associated with each data item. The method of claim 2, One or more watermarks 230 may be A robust watermark configured to cause the removal of the robust watermark to cause modulation of the associated data item, Wherein the modification of the associated data item comprises a soft watermark configured to cause modulation of the soft watermark. The method of claim 1, Combining the plurality of data items 210, Generating (340) a globality parameter (232) corresponding to the plurality of data items (210). The method of claim 4, wherein The wholeness parameter 232 is based on a hash function. The method of claim 4, wherein Each data item includes one or more data sections 220, Each data section of one or more data sections 220 has an associated section parameter 234, The totality parameter (232) comprises a hash of a complex of section parameters (234) associated with one or more data sections (220) of each data item. The method of claim 6, And the section parameter 234 of the one or more data sections 220 comprises a random number. The method of claim 6, Wherein the complex of section parameters 234 comprises a hash of each section parameter 234. The method of claim 1, The plurality of data items (210) comprises a plurality of at least one of digitally encoded audio content and digitally encoded video content. The method of claim 1, Combining each data item of the plurality of data items 210 includes: Assigning 320 a random number 234 to each section of each data item; Generating a section hash parameter 240 corresponding to a hash of the random number 234 of each section, Storing (370) the section hash parameter 240 of each section on the record carrier, Generating a globality parameter 232 corresponding to the complex of section hash parameters 240 of each section, Generating one or more watermarks 230 corresponding to each section based on the overallness parameter 232 and the random number 234 of the section; Storing (360) each section of each data item having its corresponding one or more watermark (230) on a record carrier. The method of claim 10, One or more watermarks 230 may be A robust watermark configured to cause the removal of the robust watermark to cause modulation of the associated data item, Wherein the modification of the associated data item comprises a soft watermark configured to cause modulation of the soft watermark. In a method of encoding content material, Encoding a plurality of data items 210 to form a self-referenced data set that facilitates determining whether the entire data set is present within a subsequent copy of the data set. . The method of claim 12, The self-referencing data set comprises one or more hash values (240) corresponding to data items of the plurality of data items (210). The method of claim 12, The self-referencing data set includes one hash value (232) corresponding to the plurality of data items (210). The method of claim 12, The plurality of data items (210) comprises a plurality of at least one of digitally encoded audio content and digitally encoded video content. The method of claim 12, The self-reference data set comprises as a watermark (230) the result of encoding at least one hash value (232, 240). The method of claim 16, Watermark 230, A robust component of the watermark 230 configured to cause the removal of the robust watermark to cause modulation of the associated data item, Wherein the modification of the associated data item comprises a soft component of the watermark (230) configured to result in a modulation of the soft watermark. A method of decoding content material from a source, the method comprising: Determining (410-465) whether the entire content material exists at the source; Decoding (470) the content material depending on whether the entire content material is present in the source. The method of claim 18, Determining whether or not the entire content material exists, Reading 440 an overall parameter 232 corresponding to the content material; Reading 410 a plurality of item parameters 240 corresponding to items of content material; Determining a totality value from the plurality of item parameters 240 (420); Comparing the totality parameter (232) with the totality value. The method of claim 19, Globality parameter 232 includes a hash parameter corresponding to the content material, Determining the totality value, Computing a hash value corresponding to the plurality of item parameters (240) to produce an aggregate value. The method of claim 19, Determining whether or not the entire content material exists, Reading 450 an identification parameter 234 from each item selected from among a plurality of items including content material; Comparing the identification parameter (234) of each item selected from the plurality of items with an identifier based on a corresponding item parameter among the plurality of item parameters (240). The method of claim 21, The plurality of item parameters 240 include a plurality of hash parameters, Wherein each hash parameter of the plurality of hash parameters corresponds to a hash of an identification parameter (234) of each item containing content material. The method of claim 18, Determining whether or not the entire content material exists, Reading 440 a first data set identifier 232 from a first item of content material; Reading 440 a second data set identifier 232 from a second item of content material; Determining a match between the first data set identifier and the second data set identifier. The method of claim 18, At least one of a globality parameter (232) and a plurality of item parameters (240) is inserted as a watermark (230). The method of claim 24, Watermark 230, A robust component of the watermark 230 configured to cause the removal of the robust watermark to cause modulation of the associated data item, Wherein the modification of the associated data item comprises a soft component of the watermark (230) configured to result in a modulation of the soft watermark. The method of claim 18, Determining whether the entire content material is present at the source, Reading 410 a plurality of section hash parameters 240 from a source; Calculating a totality value based on the plurality of section hash parameters 240 (420); Selecting (430) at least one selection section (220) of the content material; Reading 440 the watermark value 232 of at least one randomly selected section from the source; And comparing (445) the totality value with the watermark value (232). The method of claim 26, Determining whether the entire content material is present at the source, Reading 450 a second watermark value 234 of at least one selection section 220 from a source, Generating a hashed watermark value by hashing the second watermark value 234; And comparing (455) the hashed watermark value with one section hash parameter of the plurality of section hash parameters (240) corresponding to the at least one random section. A storage medium 130 configured to include content material, Storage medium 130, A self referencing data structure 200 configured to include a plurality of data items 210 of a data set corresponding to the content material, Each data item includes one or more data sections 220, Each data section of one or more data sections 220 has an associated section parameter 234, The totality parameter 232 is based on the complex of the section parameters 234 of the plurality of data items 210 and whether the entire data set is present within a subsequent copy of the data obtained from the storage medium 130. Storage medium, characterized in that configured to facilitate determining. The method of claim 28, Storage medium 130, characterized in that the complex of section parameters 234 is based on a hash of each section parameter 234. The method of claim 28, Storage medium 130, characterized in that at least one of the totality parameter 232 and the section parameter 234 of each data item is inserted into at least one watermark 230 associated with the data item. The method of claim 30, At least one watermark 230, A robust watermark configured to cause the removal of the robust watermark to cause modulation of the associated data item, Storage medium 130, characterized in that the modification of the associated data item comprises a soft watermark configured to cause modulation of the soft watermark. The method of claim 28, The plurality of data items (210) comprises a collection of at least one of digitally encoded audio content and digitally encoded video content. A selector 112 configured to select a plurality of data items 210 to produce a data set having a minimum size that discourages transmission of the data set over a limited bandwidth communication path; Corresponding to the plurality of data items 210, the binder 116 is configured to generate one or more parameters 230, 240 to facilitate determining whether the entire data set is present in the decoder 120. Wow, An encoder comprising a recorder 114 configured to combine one or more parameters 230, 240 with a plurality of data items 210 to produce a self-referenced data set stored on a recorded medium. (110). The method of claim 33, The recorder 114 stores one or more parameters 230 and 240 as one or more watermarks 230 associated with one or more data items of the plurality of data items 210 on the recorded medium. The encoder 110, characterized in that configured to store in. The method of claim 33, One or more watermarks 230 may be A robust watermark configured to cause the removal of the robust watermark to cause modulation of the associated data item, Encoder 110, characterized in that the modification of the associated data item comprises a soft watermark configured to cause modulation of the soft watermark. The method of claim 33, The encoder (110), characterized in that the one or more parameters (230, 240) comprise an overall parameter (232) corresponding to the plurality of data items (210). The method of claim 33, The encoder (110), characterized in that the one or more parameters (230, 240) comprise a plurality of section parameters (234, 240) corresponding to the plurality of data items (210). The method of claim 37, The one or more parameters (230, 240) further comprise an overall parameter (232) based on a complex of a plurality of section parameters (234). The method of claim 38, Encoder (110), characterized in that the composite (234) of the plurality of section parameters includes a hash of each section parameter. The method of claim 37, Wherein each of the plurality of section parameters 234 includes a random number associated with a corresponding data item. The method of claim 33, The plurality of data items (210) comprises a plurality of at least one of digitally encoded audio content and digitally encoded video content. A renderer 122 configured to receive data items 210 corresponding to the self-referenced data set and to generate a performance corresponding thereto from at least one of the data items 210; And an integrity checker 126 operatively connected to the renderer 122 and configured to prohibit the playing of at least one of the data items 210 depending on whether the entire data set is present. Decoder 120 to be used. The method of claim 42, Integrity checker 126, Read the globality parameter 232 corresponding to the data set, Read a plurality of item parameters 240 corresponding to the items in the data set, Determine the totality value from the plurality of item parameters 240, A decoder (120), characterized in that it is configured to compare the totality parameter (232) and the totality value. The method of claim 43, Integrity checker 126, Reading the identification parameter 234 from each item selected from among the plurality of items including the data set, And the identification parameter 234 of each item selected from among the plurality of items is compared with an identifier based on a corresponding item parameter among the plurality of item parameters 240. The method of claim 44, Globality parameter 232 includes a hash parameter corresponding to the data set, The totality value is a decoder (120), characterized in that it comprises a hash value corresponding to the plurality of item parameters (240). The method of claim 44, The plurality of item parameters 240 include a plurality of hash parameters, Each hash parameter of the plurality of hash parameters corresponds to a hash of a value associated with each item of the items of the data set. The method of claim 44, At least one of the globality parameter (232) and the plurality of item parameters (240) is encoded as one or more watermarks (230) inserted into the data set. The method of claim 47, One or more watermarks 230 may be A robust watermark configured to cause the removal of the robust watermark to cause modulation of the associated data item, Decoder 120, characterized in that the modification of the associated data item comprises a soft watermark configured to cause modulation of the soft watermark. The method of claim 42, Integrity checker 126, Read the first data set identifier 232 from the first of the data items 210, Read a second data set identifier 232 from a second of the data items 210, A decoder (120) configured to prohibit the playing of at least a second item depending on a match between the first data set identifier (232) and the second data set identifier (232). The method of claim 42, The plurality of data items (210) comprises a plurality of at least one of digitally encoded audio content and digitally encoded video content.