Copy prevention method and apparatus of a digital recording/reproducing system employing a marker including copy protection information and code data for descrambling

[0002] This reissue application is related to concurrently filed reissue application No.

[0003] 1. Field of the Invention

[0004] The present invention relates to a copy prevention method and apparatus of a digital magnetic recording/reproducing system, and more particularly to a copy prevention method and apparatus of a digital magnetic recording/reproducing system, wherein a marker involving copy prevention function information and executing the function is coded and inserted to perform the copy prevention function and realize the copy prevention function of various patterns desired by a program supplier.

[0005] 2. Description of the Prior Art

[0006] One example of a conventional copy prevention method is described in U.S. Pat. No. 4,819,098, in which a signal inducing an interference to an automatic gain controller (AGC) circuit within a VCR is inserted to a video waveform to be recorded on a tape. When the tape is reproduced to display the signal on a television, the interference signal does not affect the AGC circuit of the television to allow , allowing for a normal display.

[0007] However, when the reproduced signal is recorded by another VCR, i.e., when it is duplicated, the interference signal brings about the interference in the AGC circuit of the recording VCR to record in causing an inaccurate signal level to be recorded. Accordingly, the nodal display cannot be attained when reproducing a duplicated tape.

[0008] As another example, U.S. Pat. No. 4,571,642 utilizes a control track employed during performing the reproduction for synchronizing a servo circuit within a VCR, thereby for embodying the copy prevention function. The basic concept of this patent is for altering a video signal to force the control track to be inaccurately recorded when the video signal is duplicated onto another tape.

[0009] Still another example is disclosed in U.S. Pat. No. 4,577,216, in which a phase noise or the like is inserted to in a chroma burst portion of a video signal to thereby embody the copy prevention function.

[0010] The above-mentioned methods are for using using a difference of between the sensitivity between of circuits of in a television and of a VCR. Thus, the copy prepared to prevent the copy thereof as above may not exert the copy prevention function in a certain VCR, but may not execute a normal display on a certain television.

[0011] The above copy prevention methods are of an analog system, which are available for preventing the copy of an NTSC-class video signal to an analog VCR. However, in case of a high-definition image of the analog television (ATV), the copy is performed by means of a digital VCR rather than an analog VCR, so that it is difficult to employ the copy prevention method of the analog system.

[0012] Therefore, it is an object of the present invention to provide a copy prevention method and apparatus of a digital magnetic recording/reproducing system applicable to a digital VCR and incorporated with various copy prevention functions to enable the selection of a copy prevention function desired by a program supplier.

[0013] To achieve the above object of the present invention, there is provided a copy prevention method of a digital magnetic recording/reproducing system, which is performed by an audio and video signal transmitting process and an audio and video signal receiving/recording process. The audio and video signal transmitted process is carried out in the sequence of encrypting a marker formed by a control word for scrambling audio and video bit strips and copy prevention information for preventing an illegal copy by means of an encoding key, and multiplexing the marker with the audio and video bit strips scrambled by the control word. Then, the audio and video signal receiving/recording process is performed in the sequence of detecting the marker from the transmitted bit strips, decrypting and analyzing the detected marker by means of an encoded key to determine whether copy copying is permitted or not, updating the detected marker to be recorded on a video tape, and generating the control word from the marker to perform a descrambling and supply the audio and video signals to be displayed on a monitor.

[0014] Also, a copy prevention apparatus of a digital magnetic recording/reproducing system includes a marker detecting and inserting part for detecting a marker from input bit strips, and inserting the updated marker to the bit strips to output the result. A marker analyzing and processing part decrypts and analyzes the encrypted marker from the marker detecting and inserting part by means of an encoded key, outputs a control word for descrambling the bit strips, and updates and encrypting the decrypted marker by means of the encoded key to output the result. In addition, a buffer part buffers the control word and updated and encrypted marker from the marker analyzing and processing section, and inserts the updated and encrypted marker in the marker detecting and inserting part, and a descrambler descrambles the bit strips provided via the marker detecting and inserting part by means of the control word from the buffer part.

[0016] These and other objects are further achieved by providing a method of processing copy protected digital data, comprising receiving digital data said digital data including copy prevention information; determining from said copy prevention information whether copying is permitted; updating said copy prevention information if said determining step determines that a copy is permitted; inserting said updated copy prevention information in place of said copy prevention information only in said digital data for recording; and recording output from said inserting step.

[0017] These and other objects are still further achieved by providing an apparatus for copy protecting digital data, comprising a copy prevention generator generating copy prevention information; a control data generator generating control data; a scrambler scrambling digital data based on said control data; marker forming means for forming a marker, said marker including said copy prevention information and said control data; and a transmitting unit transmitting said scrambled digital data and said marker.

[0018] In an alternative embodiment, the scrambled digital data and the marker are recorded.

[0019] These and other objects are still further achieved by providing an apparatus for processing copy protected digital data, comprising a receiving unit receiving digital data, said digital data including copy prevention information; an analyzing unit determining from said copy prevention information whether copying is permitted, and updating said copy prevention information if a copy is permitted; an inserting unit inserting said updated copy prevention information in place of said copy prevention information only in said digital data for recording; and a recording unit recording output from said inserting unit.

[0020] The above objects and other advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which:

[0021] FIG. 1 is a flow chart illustrating an audio and video signal transmitting process in a copy prevention method according to the present invention;

[0022] FIG. 2 is a flow chart illustrating an audio and video signal receiving and recording process in the copy prevention method according to the present invention;

[0023] FIG. 3 is a view showing a structure of transport bit strips according to the present invention;

[0024] FIG. 4 is a block diagram showing a schematic construction of a copy prevention apparatus according to the present invention;

[0025] FIG. 5 is a block diagram showing a detailed construction of FIG. 4; and

[0026] FIGS. 6A to 6F are signal waveforms of respective parts shown in FIG. 5.

[0027] A copy prevention method and apparatus of a digital magnetic recording/reproducing system according to the present invention emphasizes a fact that a DVCR can record all diverse signals on a video tape, so that a variety of input signals are largely classified into two, and different use a copy prevention methods are performed for each signal method based on the type of input signal.

[0028] First, signals transmitted from a terrestrial broadcasting system, a satellite broadcasting system and a pay television broadcasting system are classified as a broadcasting signal signals, and the following three copy prevention functions are applicable when recording the a broadcasting signal.

[0029] Three The three copy prevention functions are a no recording onto a video tape permitted, a free record/copy onto the tape , and a single generational recording onto the tape with no copy of the recorded tape .

[0030] Here, the third copy prevention function of the single generational recording onto the video tape with no duplication of the recorded tape is for enabling the signal from a television receiver to record on the tape be recorded once but inhibiting the re-recording of the signal by means of another , for example, a DVCR is prohibited while the firstly-recorded tape signal can be reproduced to watch through a monitor.

[0031] A second classification is for, for example, a rental tape to be identified by a pretaped signal. Here, the copy prevention function of the pretaped signal is similar to the above no recording onto the tape and the free record/copy onto the tape copy protection function, which and has the following three copy protection functions.

[0032] The three functions are no copy onto another tape, free copy to another tape and a single generational copy to another tape.

[0033] The single generational copy function to the other tape is of the copy prevention function for allowing a allows duplication from the original rental tape , but inhibiting inhibits another copy from the duplication, which is utilized in a digital audio tape (DAT) duplicate.

[0034] The present invention is advantageous in that a program supplier selects the above functions when providing a program. For this purpose, the program supplier inserts desired copy prevention function information, i.e., a marker, into a predetermined field within the program.

[0035] The marker inserted to transport data by the program supplier prior to being transmitted is encoded, and, in order to impede an illegal copy, an encoding key for interpreting the marker is transferred via a separate transmission line such as telephone line by a prescribed period interval, e.g., once a month, to be stored within a copy prevention apparatus.

[0036] In a system having an ATV decoder incorporated in a body with, for example, the DVCR in a body , a copy prevention apparatus for embodying the copy prevention functions executes a digital copy prevention function during an interface process between the ATV decoder and the DVCR, and . The copy prevention apparatus decodes and determines the marker of a received program by means of a received encoded encoding key to perform another function in accordance with respective copy prevention functions.

[0037] The copy prevention method of the digital magnetic recording/reproducing system according to the present invention is performed through an audio and video signal transmitting process as shown in FIG. 1, and an audio and video signal receiving and recording process as shown in FIG. 2.

[0038] The audio and video signal transmitting process is for encrypting the marker formed by a control word for scrambling audio and video bit strips and copy prevention (hereinafter simply referred to as “CP”) information for preventing an illegal duplication by means of an encoded key to multiplex and transmit the audio and video bit strips scrambled by the control word. Here, the marker is already formed by a program producer to be multiplexed and transmitted together with the audio and video bit strips.

[0039] In more detail, as shown in FIG. 1, the audio and video signal transmitting process is carried out in the sequence of an audio/video bitstrip encoding step 1 for encoding the audio and video bit strips, a control word generating step 2 for generating the control word for scrambling, and a scrambling step 6 for scrambling the encoded audio and video bit strips by means of the generated control word. Successively, a CP information generating step 3 generates the CP information for preventing the illegal copy, and marker producing and encrypting. steps 4 and 5 generates respectively generate the marker by using the generated control word and CP information and encrypts encrypt the resulting marker by means of the encoded an encoding key. Finally, a multiplexing and transmitting step 7 multiplexes the scrambled audio and video bit strips and encrypted marker to transmit the result.

[0040] The audio and video signal receiving and recording process is performed in such a manner that the marker is detected from the transmitted bit strips and is decrypted by means of the encoded encoding key and analyzed. Thus, it is determined whether the copy is permitted or not to update the detected marker to be recorded on a video tape , the detected marker is updated accordingly, and the control word is produced from the marker to carry out the descrambling and display the signals on a monitor, in which . As a result, the audio and video signals transmitted from the program producer are recorded or displayed in accordance with the marker.

[0041] More specifically, as shown in FIG. 2, shows the audio and video signal receiving and recording process is performed by in detail. As shown, the process includes marker detecting steps 11 and 12 for detecting the marker by demultiplexing the transmitted bit strips, and decrypting the marker by means of the encoded encoding key, and a marker analyzing step 13 for analyzing the detected marker to determine whether the a copy is permitted or not and for detecting the control word. Then, the transmitted audio and video bit strips are descrambled and decoded by using the detected control word to supply the audio and video signals in audio and video decoding steps 14 and 15. Thereafter, the detected marker is updated and encrypted by means of the encoded encoding key to be inserted in case of permitting the copy after analyzing the marker in a and inserted in the transmitting audio and video bit strips in marker inserting steps 16, 17 and 18 if copying is permitted.

[0042] The above-stated process will be described in detail below.

[0043] To begin with, the program producer encodes the audio and video bit strips 1, generates the control word for scrambling 2, and scrambles the encoded audio and video bit strips by means of the generated control word 6.

[0044] Also, the CP information for preventing the illegal copy is generated 3, and the marker is generated by using the generated control word and CP information 4, and the coded key is utilized to perform the encryption 5.

[0045] Finally, the scrambled audio and video bit strips and encrypted marker are multiplexed 7 to be transmitted for the program recording or reproduction.

[0046] The transmitted bit strips are demultiplexed to detect the marker 11, and the encoded . The encoding key is utilized to perform the decryption and the decrypted marker is output 12. The detected and decrypted marker is analyzed to determine whether the copy is permitted or not and the control word is detected 13.

[0047] The detected control word is used for descrambling and decoding the transmitted audio and video bit strips to provide the audio and video signals to the monitor to be displayed for display 14 and 15.

[0048] In addition, when it is determined that the a copy is permitted after analyzing the marker, the detected marker is updated to be encrypted encryptedby means of the encoded encoding key, and the result is inserted to the audio and video bit strips to be recorded 16, 17 and 18.

[0049] Here, a position of inserting the marker will be observed with reference to FIG. 3.

[0050] The transmitted bit strips consists consist of transport packets of a fixed length, i.e., 188 bytes, in which a transport header is displaced on the preceding stage of the bit strips. The transport header is divided into a field of a fixed length of 4 bytes and an adaptation field of a variable length. Then, a transport-private-data field exists as one field within the adaption field. The transport-private-data field consists of an ID field and the encrypted marker. The ID field functions as a an identifier for informing that the transport-private-data field is a field utilized for the copy prevention method according to the present invention, and the encrypted marker following the ID field embodies the copy prevention function of the present invention.

[0051] When the marker is decrypted by means of the encoded encoding key, the decrypted marker is divided into a CP information area recorded with including the CP information for preventing the illegal copy, a control word area recorded with including the control word CW for descrambling, and a reserved area.

[0052] That is, the decrypted marker is formed of 8 bytes consisting of the CP information area of one byte, the reserved area of three bytes and control word area of four bytes.

[0053] At this time, the CP information is formatted by including a generational copy control field which restricts the number of permitting the copy permitted copies of the program, which . The generational copy control field is formed of an allowable generational field for limiting the copy number of the program and a current generational field representing a current generation of the duplicated program.

[0054] Next, the marker analyzing step 13 of the audio and video receiving and recording process will be described in detail.

[0055] The marker analyzing step 13 is carried out by the CP information detecting step of detecting the CP information for preventing the illegal copy from the detected marker, a copy number limiting step of comparing the allowable generation of the allowable generational field for restricting the number of permitting the copy of the program and the current generation of the current generational field representing the current generation of the duplicated program within the detected CP information to determine whether the copy is permitted or not, and the control word detecting step of detecting the control word from the detected marker for executing the descrambling.

[0056] In other words, the CP information for preventing the an illegal copy is detected from the detected marker, and the allowable generation of the allowable generational field for limiting the copy number of the program is compared with the current generation of the current generational field representing the current generation of the duplicated program within the detected CP information to determine whether the copy is permitted or not, so that the program is recorded in case of permitting the copy, otherwise the . Otherwise, reproduction cannot be executed in case of inhibiting the copy even though the recording is attained.

[0057] Next, the control word for descrambling is detected from the detected marker.

[0058] Here, the step of limiting the copy number is carried out by comparing the allowable generation of the allowable generational field with the current generation of the current generational field to determine whether the allowable generation is the current generation, inhibiting the copy when it is determined that the allowable generation is below the current generation, and permitting the copy when it is determined that the allowable generation is not below the current generation to proceed to the marker insertion step .

[0059] The copy number limiting step will be described below.

[0060] When the allowable generation is below the current generation after comparing the allowable generation of the allowable generational field preset by the program producer with the current generation of the current generational field representing the current copy number, the copy number exceeds the copy number preset by the program producer. Thus, the copy cannot be further copying cannot be permitted.

[0061] At this time, in order to inhibit the copy, the control word is destructed or is not output to block the , which blocks reproduction after performing of the copy. This is because the audio and video bit strips are recorded under the state of being scrambled, the scrambled audio and video bit strips cannot be descrambled without the control word.

[0062] Therefore, by destructing the control word, the reproduction and display cannot be achieved even though the audio and video bit strips are recorded to ; thereby have having the same effect of as impeding the recording of them.

[0063] At this time, since the control word is periodically changed in the of an interval of 0.6 second, the reproduction is impeded by destructing the succeeding control word even after accomplishing the recording.

[0064] Also, a control track within the video tape may be destructed to inhibit the copy when the recording medium is a video tape.

[0065] On the other hand, the marker is positioned on the private data field within the bit strips whenever the control word is changed.

[0066] Here, since the control word is periodically changed, the marker including the control word is received whenever the control word is changed to be supplied .

[0067] Meantime, the marker inserting step is performed by updating the marker when the copy is permitted after analyzing the marker 16, encrypting the updated marker by means of the encoded key 17, and replacing the encrypted marker with the following marker to be inserted 18.

[0068] In other words, if the copy is permitted after analyzing the marker, the current generation of the current generational field is augmented by one to update the marker 16. That is, the CP information including the updated current generational field obtained by augmenting the current generation by one is summed with the control word to be the updated marker.

[0069] The updated marker is encrypted by means of the encoded key to be replaced with encoding key and is inserted to replace the succeeding marker and inserted 17. More specifically, as the marker is supplied whenever the control word is changed, it is inserted whenever the control word is changed.

[0070] In other word words, as shown in FIG. 3, the detection of the encrypted marker and the replacement of the updated marker should be accomplished altogether on time basis.

[0071] Meanwhile, the encoded encoding key for encrypting and decrypting the marker is transmitted via a separate transmission line in a predetermined time interval and is stored to be utilized, thereby perfectly preventing the illegal copy.

[0072] That is, the marker encrypted by the encoded encoding key is transmitted and recorded together with the bit strips. Here, the control word for descrambling the scrambled audio and video bit strips is included in the marker, so that the marker should be primarily decrypted to obtain the control word. However, since the encoded encoding key for decrypting the marker is periodically changed, it is impossible to decrypt the marker without the encoded encoding key. Accordingly, it is further difficult to illegally obtain the control word.

[0073] As shown in FIG. 4, the copy prevention apparatus of the digital magnetic recording/reproducing system according to the present invention includes a marker detecting/inserting section 21, a descrambler 24, a marker analyzing/processing section 22 and a buffer section 23.

[0074] Marker detecting/inserting section 21 detects the marker from the received bit strips, and inserts to output the updated marker, i.e., the updated and encrypted marker, from buffer section 23 to the bit strips.

[0075] Marker analyzing/processing section 22 utilizes the encoded key encoding keys to decrypt and analyze the encrypted marker from marker detecting/inserting section 21, thereby providing the control word CW for descrambling the bit strips. Then, the decrypted marker is updated and encrypted by the encoded encoding key to be for output.

[0076] Buffer section 23 buffers control word CW and the updated and encrypted marker IEM from marker analyzing/processing section 22, so that the updated and encrypted marker IEM is supplied to be inserted in marker detecting/inserting section 21.

[0077] Descrambler 24 descrambles the bit strips output via marker detecting/inserting section 21 by means of the control word CW from buffer section 23 to supply the result to the monitor to be displayed or to, for example, a DVCR to record the bit strips inserted with the marker.

[0078] Here, the encoded encoding key is transmitted via the separate transmission line in at a predetermined time interval and is stored as the copy prevention method of the digital magnetic recording/reproducing system according to the present invention to double a copyright protection effect.

[0079] Referring to FIG. 3, the structure of the transport bit strips and marker will be described prior to describing the operation of the copy prevention apparatus of the digital magnetic recording/reproducing system constructed as above.

[0080] In the copy prevention apparatus of the digital magnetic recording/reproducing system, the marker is placed on the transport-private-data field within the bit strips, and the CP information area recorded with the CP information for preventing the illegal copy and the control word area recorded with the control word CW for descrambling are included thereto as shown in FIG. 3, like the copy prevention method.

[0081] Here, the CP information is formatted by including the generational copy control field for restricting the number of permitted copies of the program, which is formed of the allowable generational field for limiting the copy number of the program and the current generational field representing the current generation of the duplicated program.

[0082] The marker is formed of 8 bytes consisting of the CP information area of one byte and control word area of four bytes.

[0083] Hereinbelow, an operation of the copy prevention apparatus of the digital magnetic recording/reproducing system according to the present invention will be briefly described with reference to FIG. 4.

[0084] First, a process of displaying the input bit strips on the monitor will be described.

[0085] The input bit strips are supplied to marker analyzing/processing section 22 under the state that the marker is detected and encrypted in marker detecting/inserting section 21.

[0086] Encrypted marker EM is decrypted by means of the encoded encoding key to be analyzed in marker analyzing/processing section 22. At this time, the control word is detected from the analyzed marker to be buffered via buffer section 23 for descrambling the bit strips and is supplied to descrambler 24.

[0087] The bit strips, after detecting the detection of the marker in marker detecting/inserting section 21, are descrambled in descrambler 24 in accordance with the control word from buffer section 23, and provided to the monitor to be displayed for display.

[0088] Next, a process of recording the input bit strips via, for example, the DVCR will be described.

[0089] The process of detecting and analyzing the marker from the input bit strips is executed in the same manner.

[0090] That is, the input bit strips is are supplied to marker analyzing/processing section 22 under the state that the marker is detected and encrypted decrypted in marker detecting/inserting section 21.

[0091] Encrypted marker EM is decrypted by means of the encoded encoding key in marker analyzing/processing section 22 to detect the control word. At this time, the recording can be performed or not in accordance with the result of the analysis. If the recording is not permitted, the detected control word is destructed to impede the reproduction even though the recording can be attained. Otherwise, the current generation of the current generational field within the marker is augmented by one to update the marker, so that the encoded encoding key is utilized to encrypt the marker to supply , and the result is supplied to buffer section 23.

[0092] The updated and encrypted marker is buffered in buffer section 23 and is supplied to marker detecting/inserting section 21 to be inserted to the input bit strips.

[0093] Meantime, the control word is periodically changed in the interval of 0.6 second, and the marker is placed on the transport-private-data field within the bit strips whenever the control word is changed.

[0094] Consequently, the updated and encrypted marker is replaced with replaces the succeeding marker to be inserted .

[0095] The bit strips inserted with the updated and encrypted marker pass through descrambler 24 intact and are output to be recorded in the DVCR.

[0096] The detailed construction and operation of the copy prevention apparatus in the digital magnetic recording/reproducing system formed as above will be described with reference to the accompanying drawings.

[0097] FIG. 5 is a detailed construction view showing the copy prevention apparatus of FIG. 4, which will be described below.

[0098] Marker detecting/inserting section 21 includes a marker detector 31 which detects the encrypted marker from the input bit strips and supplies the detected marker to marker analyzing/processing section 22 and a marker detection flag signal for informing of the position of the encrypted marker within the bit strips to descrambler 24 to be . The flag is used as a reference signal of for initializing descrambler 24 while outputting the bit strips. In addition to marker detector 31, a marker inserter 32 inserts the updated and encrypted marker from buffer section 23 to into the bit strips from marker detector 31 in accordance with the marker detection flag signal from marker detector 31 to output the . The result is output to descrambler 24.

[0099] Marker analyzing/processing section 22 has a marker decoder 34 for decrypting the encrypted marker from marker detector 31 of marker detecting/inserting section 21 by means of the encoded encoding key, and a marker analyzer 34 for analyzing analyzes the CP information within the marker from marker decoder 34 to output the control word to buffer section 23 when the copy is permitted while outputting a control signal for updating the marker. Additionally, a marker updating/encoding unit 35 updates the marker from marker decoder 34 in accordance with the control signal from marker analyzer 34 to encrypt the marker by means of the encoded encoding key to output the result to buffer section 23.

[0100] Here, marker analyzing/processing section 22 further includes an encoding key storage unit (not shown) for storing the encoded encoding key to output the result encoding key to marker decoder 33 and marker updating/encoding unit 35.

[0101] Besides Also, marker analyzer 34 compares the allowable generation of the allowable generational field for restricting the number of permitting the copy of the program with the current generation of the current generational field representing the current generation of the duplicated program to determine whether the a copy is permitted or not.

[0102] Buffer section 23 includes a marker buffer 36 for temporally storing the updated and encrypted marker from marker analyzing/processing section 22 to supply it to marker detecting/inserting section 21, and a control word buffer 37 for temporally storing the control word from marker analyzing/processing section 22 to supply it to descrambler 24.

[0103] An operation of the copy prevention apparatus of the digital magnetic recording system according to the present invention constructed as above will be described with reference to FIG. 6 FIGS. 6A-6G.

[0104] FIG. 6A is a timing chart of the transmitted bit strips, FIG. 6B is of illustrates the marker detection flag m-det-flag, FIG. 6C is of illustrates the control word CW(i) from marker analyzer 34, FIG. 6D is of illustrates the updated and encrypted marker IEM(i) from marker updating/encoding unit 35, FIG. 6F is of illustrates the updated and encrypted marker IEM(i) from marker buffer 36, and FIG. 6G is of illustrates the control word CW(i) from control word buffer 37.

[0105] Encrypted marker EM(i) is included in the transmitted bit strips.

[0106] The transmitted bit strips including encrypted marker EM(i) is are formed as shown in FIG. 6A, which is supplied to marker detector 31 to detect encrypted marker EM(i) to be supplied to marker decoder 33. Also, marker detector 31 generates marker detection flag signal m-det-flag for informing of the position of the encrypted marker at the encrypted marker EM(i) portion as shown in FIG. 6B, so that the generated signal is supplied to marker inserter 32 together with the bit strips including encrypted marker EM(i). Also, marker detection flag m-det-flag is supplied to descrambler 24 to be utilized as the reference signal for initializing descrambler 24 by control word CW(i−1) from control word buffer 37.

[0107] Encrypted marker EM(i) is decrypted by the encoding key in marker decoder 33 to be and is supplied as decrypted marker M(i).

[0108] Decrypted marker M(i) is analyzed in marker analyzer 34 to determine whether the copy is permitted or not. In other words, marker analyzer 34 compares the CP information within decrypted marker M(i), i.e., the allowable generational field with the current generational field, and determining to permit the copy when the allowable generational field is not below the current generational field.

[0109] When the copy is permitted as above , marker analyzer 34 slightly delays control word CW(i), which is a part of decrypted marker M(i), to be supplied to control word buffer 37, as shown in FIG. 6C. At this time, marker analyzer 34 provide provides the control signal to marker updating/encoding unit 35 to control the updating of the marker.

[0110] That is, marker decoder 33 form forms decrypted marker M(i) from encrypted marker EM(i) after delaying a delay time required for the decode, and 34 generates control word CW(i) from decrypted marker M(i) 34 .

[0111] At this time, control word CW(i) is transmitted to control word buffer 37 to be stored until it is utilized in descrambler 24.

[0112] Decrypted marker M(i) from marker decoder 33 is updated in accordance with the control signal from marker analyzer 34 in marker updating/encoding unit 35.

[0113] That is, the updated data is the data recorded on the current generational field within the marker, which is obtained by adding one to the previously recorded current generation.

[0114] The marker updated as described above is encrypted, i.e., encoded, in accordance with the encoded encoding key to be supplied to marker buffer 36 as shown in FIG. 6D, slightly delayed with respect to control word CW(i) from marker analyzer 34 as shown in FIG. 6C. In more detail, the encrypted marker M(i) from marker decoder 33 is supplied to marker updating/encoding unit 35 to be generated as marker IEM(i), which is updated and encrypted after delaying the a delay time required for the encoding to be i) issupplied to marker buffer 36.

[0115] Here, the point of generating updated and encrypted marker IEM(i) and control word CW(i) from marker updating/encoding unit 35 and marker analyzer 34 does not coincide with a point of utilizing updated and encrypted marker IEM(i) and control word CW(i) in marker inserter 32 and descrambler 24, i.e., the points of performing the replaceable insertion and initialization of descrambler 24 do not coincide with each other. Thus, updated and encrypted marker IEM(i) and control word CW(i) from marker updating/encoding unit 35 and marker analyzer 34 are temporally stored in marker buffer 36 and control word buffer 37 for that time.

[0116] As shown in FIG. 6E, updated and encrypted marker IEM(i) temporally stored in marker buffer 36 and synchronized to be output is inserted by marker inserter 32 to into the bit strips from marker detector 31.

[0117] In more detail, marker inserter 32 receives the bit strips having encrypted marker EM(i) and marker detection flag signal m-det-flag from marker detector 31, and receives updated and encrypted marker IEM(i) which will be replaceably inserted to into the position of encrypted marker EM(i) from marker buffer 36, so that updated and encrypted marker IEM(i) is replacably inserted to the position of marker detection flag signal m-det-flag in the transmitted bit strips including encrypted marker-EM(i) as shown in FIG. 6E.

[0118] In other words, marker inserter 32 inserts updated and encrypted marker IEM(i) from marker buffer 37 replacing encrypted marker EM(i+1) at the position of producing marker detection flag signal m-det-flag.

[0119] Here, the replacably inserted marker IEM(i) is formed from the immediately detected preceding encrypted marker. Accordingly, as shown in FIG. 6E, the marker IEM(i) is stored in marker buffer 37 for a certain period to be and then provided to marker inserter 32.

[0120] As shown in FIG. 6F, control word CW(i−1) is temporally stored in control word buffer 37 to be synchronized prior to being output and is utilized for descrambling the transmitted bit strips from marker inserter 32 in descrambler 24.

[0121] At this time, descrambler 24 uses marker detection flag signal m-det-flag from marker detector 31 as the reference signal for initializing based on control word CW(i−1) from control word buffer 37.

[0122] More specifically, descrambler 24 must be initialized by control word CW(i−N) from control word buffer 37 during a period from the point of generating encrypted marker EM(i), i.e., from a position of detecting marker detecting flag signal m-det-flag to the point before starting payload of a transport packet, where N is a natural number greater than zero. Here, control word CW(i−N) is a control word formed from encrypted marker EM(i−N) transmitted before encrypted marker EM(i) as many as N times. The natural number ‘N’ allows for arbitrarily controlling the initializing point of descrambler 24.

[0123] In the copy prevention method and apparatus of the digital magnetic recording/reproducing system according to the present invention as described above, a program supplier can select the copy prevention function, and the field defined within a GA format is utilized. As the result, a separate format transformation apparatus for the copy prevention function is not required, and there is no increase in data amount to be recorded to perform the copy prevention function without converting, for example, the general digital VCR.

[0124] While the present invention has been particularly shown and described with reference to particular embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be effected therein without departing from the spirit and scope of the invention as defined by the appended claims.