MXPA01003898A - Copy method avoiding bit-to-bit duplication of digital data and reading device for implementing same - Google Patents

Abstract

The invention concerns a copy method avoiding bit-to-bit duplication of digital data and a reading device for implementing said method. The method is characterised in that the medium whereon the digital data are to be duplicated comprises a serial number used for formatting the read digital data before writing them on said medium. The invention is useful in particular for duplicating DVD's, CD's, magnetic tapes or the like.

Description

METHOD OF COPYING THAT PREVENTS BITIO DUPLICATION BY BIOLOGY OF DIGITAL DATA AND READING DEVICE TO IMPLEMENT THE METHOD DESCRIPTION OF THE INVENTION The present invention relates to a copying method which avoids the bit-by-bit duplication of digital data arising from a first source on a medium. This also refers to a device used to implement this method. Digital data shows the property of being able to be copied without appreciable loss of quality. Of course, copying consists of transmitting a series of binary information, namely "l" s and "0" s from the source to the recording or recording device. The errors that occur customarily during copying are easily corrected through the use of well-known error correction methods. In this way, when an information medium or a data source contains digital data, it is relatively simple to record them identically on a recordable or recordable medium. To protect digital data against illegal copying, various means are used.

Usually, the provider provides the digital data medium such as the diskette in the case of the computer software, with a mark that prevents any copying. In EP-A-0, 773, 490, a system is proposed to protect the information stored in the recording means, in which system each means comprises an identifier. Another way to protect digital data against copying is to provide them with a watermark or "tattoo", that is, with auxiliary data tied or linked to the digital data. The watermark must be non-modifiable and non-erasable. In this case, the reading of the data is done with the help of a private key that identifies the watermark. If there is any copying of the digital data marked with water, a private key is required to put the watermark back in its place on the copy, without which the copy becomes illegal, since it is devoid of the trademark. Water. The digital data copied without the watermark is no longer read by the reader since the latter does not identify the watermark where it should be located. In this way, the watermark excludes any copying without the private key. These known methods for protecting the copies are generally effective when the medium is processed by the devices dedicated to reading or recording. However, these methods do not prevent duplication by a pirate who creates a double or a clone that is as similar as possible to the original, by carrying out what is called bit by bit copying. The object of the present invention is to propose a copying method that avoids the unauthorized duplication of digital data arising from a first source on a medium, this method excludes the bit by bit copying of the digital information. The object of the present invention is also to provide a reading device comprising circuits that allow the implementation of said method. Accordingly, the object of the present invention is a copying method, which avoids the bit-by-bit duplication of the original data arising from a digital data source on a medium. According to the invention, the method comprises a step of formatting (formatting) the digital data arising from the digital data source, as a function of a serial number contained in said medium, and a step of writing the data with format over the medium. According to a preferred embodiment, the serial number is recorded in a non-falsifiable manner on the medium during its manufacture. To avoid piracy as much as possible, the serial number is a unique number for each medium or shows a low probability of being common to two media. In addition, the format mapping of digital data that will be duplicated, is carried out using a secret key coding algorithm such as DES or a public key algorithm such as RSA, the coding key being dependent on the serial number. Preferably, the encryption key is further dependent on a secret parameter that is contained in any reading device adapted to read the digital data that arises from the data source. The present invention also relates to a copying method that avoids bit-by-bit duplication of the digital data read by a reading device and copied onto a medium, characterized in that the medium comprises a serial number and because the copying method comprises the following steps: the sending of the serial number recorded or recorded on the medium, to the reading device, the format assignment of the digital data measured with the help of the serial number, and the recording on the medium of the digital data with format. According to a preferred embodiment, the format allocation step is carried out in the reading device. Said reading device also comprises the means that make it possible to read the medium containing the digital data with format. According to a further feature of the method according to the present invention, before performing the duplication of the digital data, the method comprises a step of verifying the authorization to copy.

The present invention also relates to a reading device that allows the implementation of the copying methods described hereinabove. According to this aspect of the invention, the device comprises a format allocation circuit adapted to receive the serial number of the medium on which the digital data will be copied and providing, as output, the data with format that are dependent of the serial number and are intended to be copied over the medium. The invention also relates, according to another aspect, to a recording medium for digital data, comprising a serial number which is unique or shows a low probability of being common with that of another means, characterized in that it also comprises the digital data recorded, formatting the digital data as a function of the serial number and a secret parameter. Other features and advantages of the present invention will become apparent upon reading the description of a given preferred embodiment with reference to the accompanying drawing herein in which: Figure 1 is a block diagrammatic view of a reading device and a recording device that allows the copying of a first medium onto a second medium. The present invention will be described while reference is made to the reading of the digital data recorded on a digital medium such as a DVD, which means Ditital Versatile Disk and copied on a second virgin medium which also consists of a DVD which in this case must be recordable, namely a DVD-R. However, it is obvious to the person skilled in the art that other sources of digital information may be used, in particular digital information that arises from a decoder and sent by a "diffuser" or digital information stored on the medium such as a magnetic tape, a recordable or non-recordable optical disc, namely a compact disc (CD), a CD-R, CD-RW, DVD, DVD-R, a magneto-optical disc or the like. The recording medium consists of a recordable magnetic tape, a CD-R, a CD-RW, a DVD-R or a magneto-optical disc that allows the storage of the audio and / or video information in digital form.

As shown in Figure 1, the copying method according to the present invention makes it possible to copy the digital information D recorded on a DVD 1, by using a reading device 2 provided with a formatting circuit 3 and the FD data that can be duplicated, are recorded on a DVD-R 4 inserted in the recording device 5. In accordance with the present invention, the DVD-R 4 consisting of a virgin DVD-R, comprising a number of series that is recorded or recorded in a non-falsifiable manner during the manufacture of the DVD-R. This serial number that is chosen in such a way as to be unique or to show a very low probability of being present on two different media, is stored in a hidden area of the disc, such as the area called the "guide area", namely the track guide. As explained in more detail later herein, this serial number is used to format the digital data read from the original DVD 1. In accordance with the method claimed in the present invention, the data read on the DVD 1 by the reading device 2 is sent to a format allocation circuit 3 which carries out a format mapping of the data by use of the serial number read on the virgin DVD-R. The FD data formatted or formatted in a specific manner, are thus obtained at the output of the reading device and are sent to the recording device 5, where these are recorded on the DVD-R 4. To carry out an assignment of format of the data such that the data recorded on the DVD-R can not be copied bit by bit but can nevertheless be read again subsequently by the reading device, namely to make a so-called legal copy, various format allocation processes can be used. One of the conventional format assignment processes is a secret key encoding algorithm such as DES which means "Data Coding Standard" which is well known to the specialists. To avoid any copying by a pirate, the key used in this case will be a key built with the help of a secret key and the serial number read on the virgin DVD-R. To carry out the format assignment using this algorithm, the data recorded or recorded on the original DVD is divided into 64-bit blocks and then formatted by the DES using a 56-bit key obtained from the serial numbers. Formatted or encoded 64-bit data packets are obtained at the output and recorded in the manner of the recording device 5 on the DVD-R 4. If the key consists of the serial number itself, the serial number will comprise 56 bits. However, the number of bits of the serial number is given as an example. Of course, it is possible to apply the invention to media whose serial numbers have lengths greater than or less than 56 bits. In this case, a truncation or channel coding can be applied to put these serial numbers to the correct length. If the key is, for security reasons, a function of the serial number, it can be obtained as follows: Since the NS is the serial number of the recording medium, and PS is the parameter stored in a secure manner in the Lean reading devices: NS and PS are concatenated to have a word (NS / PS), a hodge-podge or stir function is applied such as the SHA-1 function (standard of the National Institute of Standards and Technologies) and this results in the word SH (NS / PS) which has the length of 64 bits, and this word is truncated to have a word of 56 bits that will serve as a key for the DES. The length of the binary word NS and PS is not fixed, since SHA-1 does not need an accurate length for the input word. Function f accommodates any length of serial number. The legally copied DVD-R 4 can thus be read by the reading device 2 and the original digital data is retrieved using the corresponding decoding algorithm. It is also possible to carry out the formatting of the digital data to be duplicated by the use of a public key algorithm such as the RSA algorithm. This public key algorithm is an asymmetric algorithm which, when the public key is known, prevents the easy copying of formatted data during reading by the reading device 2. Since the data located on the DVD-R copy they do not have the same structure as the data of the original DVD, it is therefore not possible to retrieve them with a reading device different from a readout device. Also, if a bit-by-bit copy of the original DVD has been made, the reading device of the present invention does not recover the original digital information and will not read the copy. According to a further feature of the present invention, the copying method can be preceded by a step of verifying the authorization to copy, such as that described in French patent application No. 98-11860 filed on September 23, 1998 on behalf of THOMSON multimedia, and entitled "Protection against the copying of numerical data stored on an information medium." "Protection against the copying of digital data stored on an information medium." This verification of the authorization to copy is applied to an information medium comprising a first identification of a digit of the digital data, a second identification of a watermark of the digital data, a first determination of a first mark if it has been possible to identify the figure and the watermark, a third identification of a type of information medium, a second determination of a second mark if it has been possible to determine the first mark and if it has been possible to identify a particular type of information medium, a fourth identification of the cryptographic signature data that accompanies the digital data, a third determination of a third mark if it has been possible to determine the second mark and whether it has been it is possible to identify a cryptographic signature date and a first delivery of the permission for the digital copying of the digital data, if it has been possible to determine the third mark. All the features described in this French patent application are incorporated in the present patent application to carry out the verification of the authorization to copy. According to the present invention, the device 2 for reading the digital data that can be a DVD player, a decoder, a CD player or the like, comprises a format allocation circuit 3 consisting essentially of an integrated circuit including all the means required to carry out the chosen algorithm for the format assignment and make it possible for it to store in a certain non-falsifiable way, the data such as a secret key or the means for authorizing the copying. The embodiment described hereinabove is given by way of example and may be modified without departing from the scope of the appended claims herein.

Claims (11)

1. A method of copying that avoids the bit-by-bit duplication of the digital data arising from a digital data source on a medium, the method characterized in that it comprises a step of formatting the digital data arising from the digital data source, as a function of the serial number contained in the medium and a step of writing the formatted data on the medium.

2. The method according to claim 1, characterized in that the serial number is recorded or recorded in a non-falsifiable manner on the medium during its manufacture.

3. The method according to any of claims 1 and 2, characterized in that the serial number is a unique number for each medium or shows a low probability of being common to two means.

4. The method according to any of claims 1 to 3, characterized in that the step of assigning format to the digital data to be duplicated is carried out using a secret key coding algorithm such as DES or a key algorithm. public such as RSA.

5. The method according to claim 4, characterized in that the coding key is dependent on the serial number.

6. Method according to claim 5, characterized in that the coding key is further dependent on a secret parameter contained in any reading device adapted to read the digital data arising from said source.

7. A method of copying that avoids the bit by bit duplication of the digital data read by a reading device and copied on a medium, characterized in that the medium comprises a serial number and because the copying method comprises the following steps: serial number engraved on the medium towards the reading device; the formatting of the digital data read with the help of the serial number; and the recording of digital data with format, on the medium.

8. The method according to claim 7, characterized in that the step of format assignment is carried out in the reading device.

9. The method according to any of claims 7 or 8, characterized in that the reading device comprises the means that make it possible to read the medium containing the formatted digital data.

10. The method according to any of claims 7 to 9, characterized in that before carrying out the duplication of the digital data, it comprises a step of verifying the authorization to copy.

11. A reading device that allows the implementation of a copying method according to any of claims 1 to 9, characterized in that it comprises a format allocation circuit adapted to receive the serial number of the medium on which the copies will be copied. digital data, and providing as output, the formatted data that are dependent on the serial number and are intended to be copied over the medium.