This invention relates to computer-readable medium provided with a memory area like a CD-ROM, a floppy disk, a cassette, a CD, a mini-disk and a DVD. For the sake of simplicity, hereinafter, these media will be called "data carriers".

Such a data carrier comprises data, e.g., in the form of computer software to be loaded into a computer of a user who bought it. However, in practice, often the data available on such a data carrier can be read many times whereas the producer of the data wishes to be paid again for every new loading in another computer. Nowadays, buyers are often signing a kind of contract promising not to infringe the copyright associated with the data. However, that is not a technical hindrance to illegal copying of the data. In practice, large-scale checking of illegal copies at the premises of, especially, end-users is almost impossible.

European patent application EP 0849 734 A2 describes a DVD disk into which at the centre a transponder is physically attached or embedded. Once the DVD is input to a media player, the media player transmits an interrogation signal to the transponder. The transponder then accesses information from its memory once empowered with the interrogation signal and transmits the information back towards the media player, more particularly towards an interrogator located therein. The interrogator sends the information to a conditional access management processor (CAMP), and simultaneously instructs the player to access data at a predetermined address on the disk. The media player only plays if there is a match between the read data and a code processed by the CAMP as it provides the correct algorithm to decrypt the content of the DVD.

International patent application WO99/38162 describes a disc security chip embedded on a media recording disc, like a DVD, and a method for protecting access to content recorded on the media recording disc. The content on the disc is encrypted with a key, which is stored in encrypted entitlement control messages (ECM's) in a disc data stream. Different sections of the content of the disc are encrypted with a set of random keys. The random keys are, themselves, encrypted with a content key and then included in the ECM's.

American patent US 5,862,117 describes a compact disc comprising an annular region and a central region. In the annular region, a data storage medium is situated, while the central region is arranged with an electronic module, e.g. an integrated circuit, and an antenna. The electronic module comprises an identification code and/or decoding key for data contained in the data storage medium. The electronic module further allows contactless electromagnetic coupling with an electromagnetic wave transmitter-receiver.

International patent application WO97/41562 describes a data storage medium in the form of a (re)writable CD. The CD consists of a layer for data storage, a chip, and a CD coupling element for contact-free transmission of data between the chip and a data processing device. Examples of a CD-coupling element include a coil, an electrostatic coupling surface or an optical coupling element. By inserting the CD in a suitable CD-drive comprising a similar coupling element, data can be read out.

American patent US5,790,489 describes a compact disk including a processor, a transmission element, a charging array, a photosensitive array for generating a current in the charging array upon illumination with a laser, and a storage element. The current generated in the charging array is supplied to the storage element, which, in its turn supplies the processor with power. The processor controls the transmission element to impart an information signal to a compact disk reader, e.g. a cryptographic key.

Japanese patent application JP11161551 describes a CD-ROM provided with an antenna coil connected to an integrated circuit element. The integrated circuit element is powered by the antenna coil via electromagnetic induction and arranged to receive data signals. Key information stored in a built-in memory of the integrated circuit element is transmitted through the antenna coil to a storage medium driving device without contacting in response to the received data signals. The key information defines a procedure of decoding disk data and enables the storage medium driving device to decode read disk data.

It is an object to provide technical means that provide a strong protection against illegal copying of data on the data carrier.

The invention is defined by the claims.

Hereinafter, the invention will be explained with reference to some drawing which are intended to illustrate the invention and not to limit its scope.

• Figure 1 shows a data carrier provided with a distinct microprocessor to protect its data from illegal copying, as well as a system to read data from the data carrier;
• Figure 2 schematically shows the microprocessor embedded in the data carrier;
• Figure 3 schematically shows an alternative data carrier with additional microprocessor;
• Figure 4 schematically shows a possible data flow between the memory area of the data carrier, the microprocessor on the data carrier and the system arranged to read and decrypt data from the data carrier;
• Figures 5 and 6 show flow diagrams of methods of the invention.

The invention relates to digital data storage devices in which digital data, possibly organized in distinctly referably sections, is stored. The data may be retrieved in some form by a computer system and then used by a user. Figure 1 schematically shows some key elements. Figure 1 shows a circular shaped data carrier 1, like a CD, or CD-ROM, having data stored in a memory area 2. The data may comprise both executable codes once loaded in a computer and non-functional data, like text, music and pictures.

In accordance with the invention, the data carrier 1 is provided with a microprocessor 3. Figure 1 shows a circular antenna 4 as communication interface for a microprocessor unit not shown in figure 1. Figure 2 shows an example of the microprocessor 3 comprising a processor unit 5 connected to the antenna 4 and a memory 7. The antenna preferably comprises one or more circular loops arranged such that they are centered about the center of rotation of the data carrier 1. The memory 7 may comprise any kind of memory like RAM, ROM, EPROM, EEPROM, etc. allowing the processor unit 5 to carry out its functions.

Preferably, the processor unit 5 itself is embedded in the data carrier structure such that it is tamper-resistant. Together with memory 7, it may be implemented as a single-chip microprocessor of a similar type as used in smart cards. As shown in figure 1, in case of a circular data carrier designed to rotate during reading, like a CD or CD-ROM, the microprocessor 3 is preferably located such that its center of gravity coincides with the center of rotation of the data carrier 1.

Preferably, the data carrier comprises an embedded physical structure 9 connected to the processor unit 5. The physical structure 9 is, e.g., made of one or more wire loops, the presence of which being detectable by the processor unit 5. If the microprocessor unit 5 is disconnected from the physical structure 9, e.g., either by removing the microprocessor 3 from the data carrier 1 or by damaging the data carrier 1, the processor unit 5 will detect that and will not be able anymore to carry out its protection function anymore. To that end, the processor unit 5 may detect the resistance of wire loops. Alternatively, the physical structure 9 may have some predetermined capacitance or inductance or any kind of (complex) impedance that can be detected by the processor unit 5. With such an additional structure 9, one cannot use the microprocessor 3 anymore after having removed it from the data carrier 1. Only reverse engineering could then provide knowledge about the content of the microprocessor 3. However, this content may be unique for each different microprocessor 3 such that reverse engineering will never be worthwhile.

Figure 1 also shows a computer arrangement 11 comprising, e.g., a separate box 16 with a processor 8, a monitor 18, and input means like a keyboard 20 and a mouse 22. The box 16 also comprises a memory 14 connected to the processor 8. The memory is shown as one black box, however, it is to be understood that memory 14 may comprise any kind of memories, like RAM, ROM, EPROM, EEPROM, etc., to allow the processor 8 to carry out its normal operations.

In some embodiments, the computer arrangement 11 may comprise a smart card reader 13 connected to the processor 8 and arranged to read a smart card 15.

The processor 8 is shown to be connected to a laser unit 10 as an interface to read data from (and possibly write to) the data carrier 1. Of course, in case another kind of data carrier then a CD or CD-ROM is used, also another kind of interface 10 must be used. A groove 12 is provided to allow the laser unit 10 to move in a radial direction across the data carrier 1, as is known to persons skilled in the art.

Apart from the interface 10, the box 16 comprises another interface unit 6 that is arranged to allow the processor 8 to communicate with the processor unit 5 on the data carrier 1 when it is inserted into the box 16 to its reading position in which data may be read from the memory area 2 on the data carrier 1 by laser unit 10.

Figure 3 shows an alternative embodiment of a data carrier according to the invention. It shows a cassette 24 with tape storing data and wound around two shafts 26, 28 as is known in the art. Again, a microprocessor 3 is embedded in the physical structure of the cassette 24. Alternatively, the microprocessor 3 may be located on the small side surface of the cassette 24.

Instead of a CD/CD-ROM as shown in figure 1 or a cassette as shown in figure 3, any other known type of data carrier, such as floppy disk, may be applied to carry out the present invention.

The processor unit 5 embedded in the data carrier 1 is programmed to control read and/or write access of the processor 8 to the data carrier memory area 2. To that end, the processor unit 5 is, preferably, arranged to generate one or more secret, cryptographic keys which are, e.g., initialized at the final stages of manufacturing of the data carrier 1 with its processor unit 5. The one or more keys are, preferably, unique to the data carrier and may be simply stored in memory 7 of the microprocessor 3 or be calculated by the processor unit 5, as will be explained hereinafter. Below, for the sake of simplicity of the description, it will be assumed that only one key is used.

At least a portion of the data in memory area 2 is stored after being encrypted by the key. The processor unit 5 may be arranged to calculate the correct key based on one or more other (master) keys in memory 7 using key related data retrieved from memory area 2 on the data carrier 1. With reference to figure 4, such key related data will be read from the memory area 2 by processor 8 from the computer arrangement 11, preferably, without using any additional authorization mechanism, and then be transferred to the processor unit 5 through the communication interface 4. By using key related data stored in memory area 2 to allow processor unit 5 to calculate the necessary key using its own master key from memory unit 7, the encryption algorithms used to conceal data to be protected on the data carrier 1 can be selected to use very long keys, like in one-time pad calculations which require keys of the same length as the protected data.

When the processor 8 of the computer arrangement 11 is instructed by a user, through its input means 20, 22, to read protected (encrypted) data from data carrier 1, it will request the processor unit 5 to generate the correct key. The processor unit 5 will calculate the correct key based on the key related data as indicated above and send the key to the processor 8. As indicated in step 40 of figure 5 the processor 8 will receive this key. Then, the processor 8 reads data from the memory area 2 of data carrier 1, step 42. As shown in step 44, the processor 8 will use the key to decrypt data read from the data carrier 1 and store the decrypted data in its memory 14. Instructions as to how to communicate with the data carrier 1 may be loaded from the data carrier 1 to the processor 8 in any way known to the person skilled in the art, e.g., by loading an execute file from data carrier 1 to processor 8.

In practice, the generation of the key by the processor unit 5 will be dependent on whether or not one or more conditions have been met. This is further explained in figure 6.

One such condition may be the time period that the data in the data carrier 1 may be read and decrypted after a predetermined date loaded in memory 7 of the microprocessor 3. The data may e.g. be a demonstration computer program which may be used during three months after which decryption will automatically be blocked.

Another condition may be the maximum number of times the data may be read from data carrier 1 and decrypted by processor 8 or any other processor external to data carrier 1. To that end, the microprocessor 3 may store such a maximum number and check whether the number of times it is requested by a computer arrangement to provide the key exceeds that maximum number. For instance, in many cases an end-user is allowed to read and decrypt the data twice, i.e., once for regular purposes and once for back up. In such cases, the maximum number equals 2.

In general, as shown in figure 6, for checking the condition to be met the computer arrangement 11 and the data carrier 1 start communicating in step 50. In order to enhance security the condition is preferably checked by processor unit 5 of the data carrier 1, step 52. Only if the condition is met the processor unit 5 will generate the required key and send it to the processor 8 of the computer arrangement 11, step 54.

In order to be sure that both the key and the decryption algorithm are never entirely known to the computer arrangement protection and control over data use may be achieved by interaction between the processor unit 5 and the processor 8 such that the processor unit 5 performs additional computations necessary for the decryption algorithm. For effective operation with respect to speed of performance, such additional computations for decryption can be performed on a selected part of the data to be protected, e.g., every first 100 bytes of each retrieved 20 kbytes. To this end, figure 4 shows the situation that part of the encrypted data from the data carrier 1 is transferred to the processor unit 5 by computer arrangement 11.

Protection may further be enhanced by introducing an authentication mechanism of the user. Then, only when the user proves his/her authenticity to the processor unit 5 the latter will provide the correct key. To that end, passwords or user codes input by the user through one of the input means 20, 22 can effectively be used. Such a pass word or user code must then correspond to a password or user code stored in memory 7.

Alternatively, a password acceptance algorithm based on additional authentication data stored in the data carrier 1 may be used. Such authentication data may be read by processor 8 from the data carrier 1 and be transferred to the microprocessor 3 (see figure 4). A password input by a user may, e.g., be checked by the processor unit 5 as being valid upon checking whether or not it belongs to a dictionary of acceptable words stored as such authentication data in the data carrier 1 possibly complemented with rules for combining them, the rules being stored as an authentication key in memory 7.

User identification may also be carried out by using the smart card reader 13 and smart card 15 that belongs to a user who knows a password associated with the smart card 15 .

As a further alternative, the smart card reader 13 may be arranged to read smart card 15 provided with an electronic purse facility and the processor unit 5 may be arranged to allow decryption of data from the data carrier 1 only when a predetermined amount of money has been paid through the electronic purse. A payment facility through the Internet is another option for paying in advance of any next decryption step.

The protection mechanism illustrated above may be expanded to providing different sets of keys for different sets of data on the data carrier.

The copy of the data to be protected and loaded in the computer memory 14 may be provided with a digital watermark calculated by the microprocessor 8 during the process of loading the data into the computer 11. The calculation algorithm used by the processor 8 to provide the watermark is derived from the data carrier 1. Alternatively, either a part of or the entire watermark is calculated by processor unit 5 and sent to the processor 8. The watermark may include the time of loading, user identity information or any other information to uniquely identify a stored copy of the loaded data. The watermark may use data elements of the data itself such that the data itself will at least be partly damaged if somebody tries to remove the watermark. The watermark serves as an identifier to locate the source of illegal copies of the data.

The processor 8 is shown to be one block. However, if preferred, the processor 8 may be implemented as several sub-processors communicating with one another each dedicated to perform a predetermined task. Preferably, the processor 8 is (or the sub-processors are) implemented as a computer with suitable software. However, if desired, it (or they) may be implemented as dedicated digital circuits.

The software running on the processor unit 5 of the data carrier 1 and on the processor 8 of the computer arrangement 11 may, prior to loading, be stored on a data carrier like a CDROM or may be distributed through a telecommunication connection (for instance entirely or partly wireless) like the Internet.