FR2732488A1 - Protection system blocking illegal use of computer program or data - Google Patents

Abstract

The protection system has a first coder that modifies the words in part at least of the program before it is recorded on the disc. The coding uses the first part of a key, and encodes the addresses of the second part of the data using the second part of the key. A coder/decoder unit is connected between the processor and the computer memory. The decoder (56) decodes the data bits when they are read from the memory by the processor, and a second coder (46) code the addresses at which are read the data bits in the memory under the second key. The buyer for the disc must first communicate a code to the vendor, who encodes the disc with this code and another code they provide to the buyer. The code is stored in EPROM in the computer.

Description

 The present invention relates to the protection of software against its illegal use and in particular a protection system preventing the use of software illegally.

 Software is a work protected by copyright and whose right of use is limited to the purchaser. However, it is well known that software purchased commercially in the form of a floppy disk can give rise to copies made with or without the agreement of the holder of the right of use, thanks to the use of techniques of system violation. protection.

 A commonly used system consists in limiting the number of copies or installations that the purchaser of the floppy disk can make by inserting a counter in the recorded data, a counter which decrements with each copy or installation so as to prohibit any copying when the counter is at zero. This type of protection is violated either by the introduction of a much higher counter value than that recorded by the designer (for example 5), or by the use of a copy program capable of avoid decrementing the counter at the time of illegal copying.

 Another system consists in introducing into the data recorded on the floppy disk, a password which only the purchaser knows and which must be entered in the computer at the beginning of the call of the software to be able to have access to said software. Unfortunately, machine language experts are able to recover the password and therefore be able to use or allow the use of the software illegally.

 This is why the object of the invention is to provide a system for protection against the illegal use of software which uses both the software and the hardware in which the software is implemented.

 The main object of the invention is therefore a protection system preventing the illegal use of software in a computer comprising a processing unit and a memory containing the software data which have been stored in the memory from a data source such as a floppy disk. This system is composed of a first coder for coding, before recording in the data source, the data bits of the software according to a first part of a coding key and coding the addresses of these data according to a second part of the coding key, and a coding / decoding unit interconnected between the processing unit and the memory of the computer comprising a decoder for decoding the data bits when they are read from the memory by the processing unit and a second coder for coding the addresses from which the data bits are read in the memory according to a second part of the key of c odor.

The objects and objects of the invention will emerge more clearly on reading the following description made with reference to the drawings in which
FIG. 1 is a block diagram of the system used for coding software preventing its use in any computer other than the computer containing the appropriate decoder, and
Figure 2 is a block diagram of a preferred embodiment of the system used for decoding coded software using the system according to the present invention.

 The essential characteristic of the invention is to provide a system of protection against the illegal use of software, using coding of the software, the key of which is incorporated in the computer alone authorized to use the software.

For coding, software whose source 10 is generally a floppy disk, but could be a line for transmitting data from a network (for example
Internet), is read by a microprocessor 12. If the software is on a floppy disk, this entry is the reader A. The bits of information coming from the software are transmitted in memory 14 using the data bus 16 after being coded by the coder 18 according to a predetermined coding key. Preferably, the coding consists in inverting or not the information bits of each data word by using an OR-Exclusive circuit per bit, the second input of each circuit being a corresponding bit of the coding key. That is, if the corresponding bit of the key is a bit 1, the data bit is inverted while it remains unchanged if the bit of the key is an O bit. Thus, with data words of 8 bits wide, the data coding key is an 8-bit word, which provides 255 coding possibilities.

 The coding key contains, in addition to the 8 bits intended for coding the data, 10 other bits which are used to codify part of the address bits supplied by the microprocessor 12 on the address bus 20. The 10 bits to be coded are therefore supplied on the bus portion 20-1 to the coder 18 oO they are coded in the same way as above, that is to say by combining them according to OR-Exclusive circuits with the 10 corresponding bits of the coding key. The other non-coded bits are supplied on the bus portion 20-2 which is recombined with the portion 20-1 at the output of the coder to constitute the address in the memory 14 to which each data word is stored after coding in the encoder 18.

 When all the software data supplied by the source 10 has been stored after coding in the memory 14, this data is transferred to a reception unit 22, generally a floppy disk in the reader B, under the control of the microprocessor 12 commanding reading the memory on the R / W line 24 and writing the data by the write command line, the data being transferred from the memory 14 to the unit 22 on the transport bus 28.

 At the same time as the file containing the coded data of the software which has been recorded (for example on a floppy disk in the drive B), the microprocessor 12 saves a file which contains the start and end addresses of the coded part among the data on the file diskette which will be used for reading as a software interrupt.

 It should be noted that, although the embodiment described above uses 8-bit data words, it is obvious that the width of the data words and the key could be different, for example 16 or 32 bits. Likewise, it is conceivable that the coded address portion is greater than 10 bits, which is possible insofar as the current memories have capacities of several megabytes, and therefore require addresses largely exceeding 10 bits. However, with an 18-bit coding key, the number of coding possibilities is already 262,144.

 In order to be able to read a floppy disk on which the coded software has been recorded, a computer must therefore be provided with a decoder capable of decoding the data according to the coding key used when the software was recorded. This is illustrated in Figure 2.

 Once the coded software has been stored in the memory 40 of such a computer, the microprocessor 42 has access to the software in the following manner. The address part formed by the first 10 bits of the address is transmitted on the portion 44-1 of the address bus 44 while the rest of the address is transmitted on the bus portion 44-2. This 10-bit address part is supplied to the address coder 46 in which each of the 10 bits is combined by an OR-Exclusive circuit with one of the 10 bits of the address part of the identical 18-bit coding key. the coding key that was used at the time of coding. Thus, the address bits supplied at the output of the address coder 46 are the same as those which were used at the time of the coding. The 10-bit part of the decoding key is permanently saved in a ROM memory. 48 and is supplied to the address coder 46 via the door 50.

 The coded address part supplied on the address bus 52 at the output of the address coder is then juxtaposed with the non-coded address part of the bus portion 44-2 to address the memory 40. The word addressed (coded) data, assumed here to be 8 bits, is then transmitted by bus 54 to decoder 56 where each of the 8 bits of the data word is combined by an OR-Exclusive circuit with one bit of the second part of 8 bits the 18-bit coding key, which was used at the time of coding. This 8-bit part of the coding key is permanently stored in a ROM memory 58 and is supplied to the decoder 54 via the door 60. The decoded data word is then supplied to the microprocessor 42 by means of the bus. 61.

 As mentioned previously, since not all of the data that has been stored in the file read from memory 40 is encoded, a file has been saved to provide the computer's operating system with the starting addresses. and end of the coded parts. Reading this file makes it possible, by means of an interrupt, to write the start address of the part coded in a register 62 and the end address of the part coded in a register 64. When the microprocessor 42 wishes read data, the address provided on the addressing bus 44-1 is also provided to the comparators 66 and 68 whose outputs are connected to the input of the AND circuit 70 so as to compare the requested address with the start and start addresses. If the requested address is outside the range delimited by the start and end addresses, one of the two comparators 66 and 68 provides an output O and the other an output 1, this which results in a bit O on the output 72 of the AND circuit 70. Consequently, in this case, the two gates 50 and 60 are blocked and exclusively bits 0 are supplied at the input of the encoder 46 and the decoder 56, which has results in providing an unencrypted address on bus 52 and a donation word not coded on bus 61.

 On the other hand, if the requested address is in the coded range between the start address stored in register 62 and the end address stored in register 64, the respective outputs of comparators 66 and 68 are at 1. Consequently, the output 72 of the AND circuit 70 is also at 1 and the gates 50 and 60 are on, which results in that the address supplied on the bus 44-1 is coded using the part (10 bits ) of the coding key located in the ROM memory 48 and the data word supplied on the bus 54 is coded by the part (8 bits) of the coding key located in the ROM memory 58.

 Note that the disk used could be a simple commercial disk with no coded part. In this case, the addresses recorded in registers 62 and 64 are the same and the AND circuit 70 always supplies an input to O preventing the coding of the data of the floppy disk.

 The system which has just been described can be implemented very simply. Either the owner of a computer has his computer modified by replacing the existing microprocessor chip with a chip comprising, in addition to the microprocessor, the coding / decoding device illustrated in FIG. 2, or the computer is already provided with such a device. In both cases, an identification number representing a coding key is provided to the owner of the computer; such a value corresponding for example to a combination of 18 bits such as that used in the description which follows. At the same time, the manufacturer or designer of the software supplies the distributors with a coding device such as that illustrated in FIG. 1. The owner of the computer wishing to acquire the software must then supply the identification number to the software distributor. so that the latter performs the coding of the software according to the coding key associated with the identification number.

It could also be envisaged that the software supplied to the distributors in the form of floppy disks, is already coded by an F1 key, which would prevent unscrupulous sellers from being able to copy the uncoded software received from the designer. In this case, the part of the coding key intended for coding the data and located in the memory
ROM 58 must result from the combination by circuits
OR-Exclusive of the F1 key and the specific key of the computer owner. One can also imagine that the software is previously coded at several levels by keys F1, F2 ... which implies having a decoding key which is the result of the different keys used for coding.

 It should be noted that the key F1 (or the combination of several keys F1, F2 ...) could be in the form of a file formed by a plurality of words, such as for example a file of 1024 words of 8 bits .

Although the invention is particularly applicable to software, it can be applied to any other file such as a personalized database. In this case, the device installed in the computer will have to decode the data read from the memory, but also encode the new data transferred to the memory. This can be done with the same circuit 56 since, whether encoding or decoding, it uses the same OR circuits
Exclusive. Consequently, the data buses 54 and 61 of FIG. 2 should then be bidirectional.

Claims (8)

 1. A protection system preventing the illegal use of software or other data files in a computer comprising a processing unit (42) and a memory (40) containing the data bits of said software, said data bits having been stored in said memory from a data source such as a floppy disk on which said software has been recorded, said system being characterized in that it comprises  a first coder (18) for coding, before their recording in the data source, the data words of at least part of said software according to a first part of a coding key and coding the addresses of said data according to a second part of said coding key, and  a coding / decoding unit interconnected between said processing unit and said computer memory, comprising a decoder (56) for decoding the data bits when they are read from said memory by said processing unit and a second coder (46) for coding the addresses from which said data bits are read from said memory according to said second part of said coding key.  2. The system as claimed in claim 1, in which said first coder (18), said decoder (56) and said second coder (46) are formed of two-input OR-Exclusive circuits, the first input being the data bit or d address to be coded or decoded and the second entry being the corresponding bit of said coding key.  3. The system as claimed in claim 1 or 2, in which said coding key is specific to said computer and said data source (10) such as a floppy disk is coded by the software vendor using said first coder using the coding key communicated by the buyer.  4. The system as claimed in claim 1 or 2, in which the data bits of said software are first coded a first time according to a predetermined coding algorithm (F1) before being coded by means of said first coder using said first part d a coding key specific to said computer and communicated by the purchaser of said software, said decoder (56) using a combination of said coding algorithm and said first part of the coding key to decode the data bits of said software.  5. The system as claimed in claim 4, in which said predetermined coding algorithm (F1) consists of a sequence of data words and its combination with said first part of the coding key repetitively combines the bits of said first part. of the coding key with the sequence of bits of the said sequence in Exclusive-OR circuits with 2 inputs.  6. System according to one of claims 1 to 5, wherein said coding / decoding unit comprises a decoding authorization device comprising registers (62, 64) indicating the start and the end of the part of the software to be coded. and comparators (66, 68) for authorizing by doors (50, 60) said second coder (46) and said decoder (56) when the addressed data are in said part to be coded and for prohibiting said second coder and said decoder when the data addressed is outside of said part to be coded.  7. System according to one of claims 5 to 6, in which the part to be coded of said software or other data file comprises portions of data which are rewritten, the data bus (54) connecting said memory (40) to said decoder. (56) and the data bus 61 connecting said decoder to said processing unit (42) being bidirectional so that the data which must be rewritten can be coded by said decoder when it is transmitted from said processing unit to said memory.  8. System according to any one of the preceding claims, in which said coding key is stored in a permanent memory of the ROM type (48, 58) in said computer.