WO1997030447A1

WO1997030447A1 - Device for protecting data on magnetic or magneto-optical media

Info

Publication number: WO1997030447A1
Application number: PCT/FR1997/000279
Authority: WO
Inventors: Philippe Escal; Dominique Escal; Jean-Edouard Robert
Original assignee: Philippe Escal; Dominique Escal; Robert Jean Edouard
Priority date: 1996-02-16
Filing date: 1997-02-14
Publication date: 1997-08-21
Also published as: FR2745112A1; FR2745112B1

Abstract

A device for protecting data stored on a medium (30) of which the contents may be altered by a magnetic field is disclosed. The device comprises a housing for said medium and a sensing means for transmitting a sensing signal when the housing is tampered with. Erasing means (14) include a current generator (9) supplying power to coils (81, 82) to generate a magnetic field around said medium. The erasing means apply a current to the turns of the coils when the sensing signal is transmitted so that a magnetic field is generated and the data is erased. The turns are arranged on either side of the data medium and can generate magnetic fields having substantially the same polarity on either side of said medium.

Description

Data protection device on magnetic or magneto-optical media.

The present invention relates to a device making it possible to prevent third parties from accessing information stored on media the content of which is liable to be modified by the action of an external magnetic field.

It applies in particular to the protection of floppy disks and computer hard disks.

The development of information technology means that users increasingly have to transport confidential information in order to use, communicate or process it in different places. The codings currently used cannot guarantee that the information thus transported will not be misused by a third party who would have it available. Indeed, these information encodings are either universal and, consequently, accessible to all, or of a very heavy use which considerably hinders normal access to data.

There are devices consisting of a housing provided with a compartment inside which is housed a floppy disk. In case of break-in of the box, an activator sends a current in the direction of coils arranged near the floppy disk, which causes the erasing of the information stored on this floppy disk. These systems, which generally comprise coils traversed by a direct current and placed only on one side of the data carrier, are insufficient because, because of the positioning of the coils, necessarily distant from certain areas of the carrier, they require a source of powerful and therefore heavy energy, which affects their portability. In addition, they do not correctly erase the data because the phenomenon of magnetic hysteresis maintains a magnetic state of low amplitude but representative of the data initially memorized.

Finally, they do not erase the identification and / or operating system areas of the medium, on which there are data necessary for the use of the information present on said medium.

However, true erasure security cannot be assured that if the erasure concerns not only the data stored by the user but also the identification and / or operating data of the medium, that is to say the part of the medium containing the information necessary for the computer to read the floppy disk.

Indeed, some software is capable of recovering data, even if some areas of the floppy disk are erased.

The object of the invention is to remedy its drawbacks by targeting a data protection device in which the particular location of the coils and the direction of the current flowing through them each ensure secure erasure of the floppy disk in the event of a break in, without overloading. substantial weight. To do this, the invention relates to a device for protecting data stored on a medium, the content of which can be modified under the action of a magnetic field, comprising a housing for housing said medium, a means detection emitting a detection signal during an unauthorized opening attempt of the housing, erasing means comprising a current generator supplying turns enabling the creation of a magnetic field in the vicinity of said support, the means of erasure being adapted to cause said turns to pass through a current following the emission of said detection signal, in order to generate a magnetic field for erasing computer data, device according to which said turns are arranged on either side of the document and are adapted to jointly generate magnetic fields whose polarities are substantially identical on either side of said support.

This arrangement which counteracts the polarities of the magnetic fields, although surprising, makes it possible to avoid a magnetic saturation of the turns and, consequently, makes it possible to generate a magnetic field of high intensity. In addition, the support on which the data is stored being magnetized, it itself causes a deformation of said fields magnetic whose polarities are identical, deformation which increases the capacity of said magnetic field to modify the magnetic state of the support. Data erasure is thus facilitated. The device according to the invention is thus particularly effective, in so far as it has two degrees of security.

In fact, the box firstly provides mechanical prevention of access to the documents concerned. In addition, if an indelicate still manages to come into possession of the documents, they are unusable since the information contained therein is then erased.

According to a preferred embodiment, the erasing means are adapted to make the turns pass successively by currents flowing in two opposite directions, the polarity of the magnetic field changing with the direction of said current.

Thanks to these provisions, the entire part of the support whose state is liable to be modified under the action of a magnetic field initially takes, when the turns are traversed by a current in the first direction, states similar magnetic, even if they retain a residue linked to the hysteresis of their previous state. Then, in a second step, when the turns are crossed by a current in the opposite direction, all the point magnetic states become identical, without keeping any trace of the initial magnetic state.

According to particular characteristics, the support comprises a predetermined number of sectors, and the turns are arranged in the form of coils, the number of which is greater than or equal to half the number of sectors.

Thus, each sector is placed, at least partially, opposite a coil and the magnetic action of each coil does not need to exceed the two sectors which are opposite it. This minimizes the amount of energy available for erasing data. According to other particular characteristics, the support has the shape of a disc, the coils have several studs positioned radially with respect to the support, the radial dimension of the coils being greater than half the radius of the support.

This embodiment applies in particular to floppy disks, hard disks and flexible disks, by optimizing the arrangement of each reel, according to the shape of the support. According to other particular characteristics, the support comprises on the one hand a data area and on the other hand an identification and / or operating system area and the magnetic field generated by the turns is liable to modify the data of the memory area and the data of the identification area and / or operating system.

Thanks to these provisions, the data which allow the use of the medium are also destroyed. According to other particular characteristics, the detection means is connected to a normal opening system of the case and emits a detection signal when said unauthorized opening attempt takes place on said opening system of the case. Thanks to these provisions, the normal opening system of the case, which is mechanically the weakest point of the case, is particularly monitored by the detection means.

According to other particular characteristics, the fixed walls of the housing are covered by conductive wires constituting a mesh network,

- The detection means is an electronic circuit detecting the variation in electronic resistance resulting from the breakage of at least one conductive wire. Thanks to these provisions, any attempt to pierce the walls of the device is detected by the detection means. According to other particular characteristics, the current generator comprises a spark gap connected to the internal face of the wall of the housing.

Thanks to these provisions, neutralization of the device by emission of high-intensity electromagnetic signals is impossible, since the spark gap prevents overvoltages on the electronic detection and erasure means.

According to other characteristics, the current generator comprises a magnetic saturation circuit connected at its input to an energy source and the output of which is connected to the erasing means.

Thanks to these provisions, the neutralization of the device by emission of high-intensity electromagnetic signals is impossible, since the saturation of the magnetic circuit prevents overvoltages on the electronic detection and erasure means.

According to other features, the housing is portable and has a handle. The description which follows, made with reference to the accompanying drawings for explanatory purposes and in no way limiting, allows a better understanding of the advantages, aims and characteristics of the invention.

- Figure 1 is an elevational view of a diskette known under the name "High Density";

- Figure 2 is a perspective view of a floppy disk and erasing coils surrounding it; Figure 3 is a schematic view of the magnetic configuration of erasing coils; - Figure 4 is a timing diagram of the currents and voltages across the erasing coils shown in Figure 3;

- Figure 5 is a schematic perspective view of coils and capacitors incorporated in a carrying case;

- Figure 6 illustrates a block diagram of the operation of the protection device according to the invention, in which the erasing means are magnetic;

- Figures 7 and 8 show block diagrams illustrating two embodiments of the device for recharging and protecting the magnetic erasing means; and

- Figure 9 illustrates a block diagram similar to that of Figure 6, in which the erasing means are electrical. For convenience and clarity, in the description which follows, the word floppy disk has been used but it includes flexible floppy disks, hard disks as well as other magnetic and magneto-optical media, known or to come, such as for example , the flexible discs currently under study.

As shown in FIG. 1, a high density commercial floppy disk, designated as a whole by the reference 30, comprises eighteen sectors 1 of equal surface. On the other hand, it includes on the face eighty concentric tracks 2 (of which only three are shown), or one hundred and sixty tracks on the set of the two faces. The data storage areas therefore correspond to the track 3 segments delimited by the sectors.

To be played, each track segment 3 must be intact, even a partial degradation of the recording preventing the entire track segment considered from being read.

To erase a given sector 1, it is therefore necessary to at least partially degrade each of its track segments 3. FIG. 2 shows the arrangement of the erasing coils around the floppy disk, omitting any mechanical protection of the floppy disk , by a cardboard sleeve or by a case, for example. In fact, these mechanical protections are permeable to magnetic fields and allow the device to operate as described in the description.

Each coil has an elongated shape and has three magnetic pads 83 on which are formed turns 84 of an electrical conductor supplied by a current emitted by an erasing means presented below.

In order to ensure the erasure of the sectors on the two sides of the floppy disk, two groups of coils 81 and 82 are placed on either side of the floppy disk 30, symmetrically with respect to the surface of the latter.

Each coil is arranged radially with respect to the disk 30, thus covering substantially half of the radius thereof. Each coil is also placed vis-à-vis with two neighboring sectors 4 and 5.

The support comprising on the one hand a data area and on the other hand an identification area and / or operating system, the magnetic field generated by the turns is adapted to erase the data from the memory area and the data of the identification zone and / or operating system.

In the embodiment shown, there are ten coils on each side of the floppy disk. The magnetic diagram of the device is presented in FIG. 3, in which two coils 81 and 82 are placed on either side of the support 30 and are supplied by an electrical supply circuit, or current generator.

9. This current generator, of known type, is adapted to successively generate positive and then negative voltages between its terminals. The electrical connections of the turns of the coils and their configuration, that is to say mainly the direction of their windings, are adapted to generate magnetic fields of the same sign on either side of the support 30, here, two magnetic fields presenting their south pole to the support 30. The control circuit of the switch 6 of the circuit presented in FIG. 3 is presented below.

The magnetic fluxes in the cores of the coils tend to cancel out while on the surface of the support 30 they cooperate to modify and erase the data stored on the support.

Figure 4 shows the timing diagrams of the voltage across the coils, curve V, and of the intensity of the current passing through said coils, curve I, when the erasing of the information is triggered, only one of the two erasing phases corresponding to opposite directions of circulation of the current, being shown here. It is observed, in FIG. 4, that the curve I, corresponding to the intensity of the current, does not present an inflection point in the part where it is increasing, which implies that there is no saturation of the nucleus coils by the magnetic flux which crosses them.

This result is linked to a general characteristic of the present invention according to which the identical polarities of the coils placed on either side of the information carrier, face each other. Thanks to this characteristic, the erasure of the data takes place over a larger surface of the support around each coil, than if the magnetic polarities on either side of the information medium were reversed.

The floppy disk and the erasing coils are housed in a box shown diagrammatically in FIG. 5.

In FIG. 5, we observe the arrangements of the most voluminous elements present in a housing 8 partially shown: the coils SI and 82, capacitors 7 and six locations 11 for six floppy disks 30, in two stages of three locations. In each location can be positioned a diskette of known format, by longitudinal sliding. Preferably, the polarities, which it is recalled that according to a general characteristic of the invention, they are identical to each other, and which face each other around the magnetic supports 30 are different for the superimposed supports, the coils 82 placed between the two supports 30 thus serving simultaneously to erase the data on the two supports which it separates.

Box 8, of external dimensions approximately equal to 31 x 18 x 6 centimeters, comprises a handle (not shown) which makes it easily transportable and a normal access opening 41, consisting of a secret code lock comprising, in known manner, a keypad, a memory retaining the authorized code and circuits for comparing the codes formed on the keyboard and the code kept in memory. When these two codes are identical, the opening of the box is authorized and the drawer containing the data carriers (here the diskettes) can be opened. It should be noted, however, that the secret device ensuring the normal opening of the case can be, for example, a combination keyboard, an electrical key contact or even a link with a computer.

When an attempted break-in occurs, the break-in detection means shown in FIG. 6, deliver a signal allowing the erasing means to send an electric current through the turns of the coils, via a magnetic circuit shown diagrammatically in FIG. 3. Each coil then allows the erasure of all the track segments of the two neighboring sectors which it partially covers, in two time intervals during which currents successively flow in opposite directions through the turns, to reverse the polarities of the magnetic fields they generate. Thus, all of the information stored on the entire floppy disk is unusable.

The security of the protection device according to the invention is therefore optimal. In addition, the weight of the entire device remains reduced, insofar as a number of coils substantially equal to the number of sectors is necessary.

As shown in FIG. 6, the protection system according to the invention is provided with an electromechanical detector 10 of the type described above, making it possible to detect the intrusion of the normal access opening 41 of the housing 8 for housing the supports 30. 10

The detector 10 is in relation to a control line 12 which allows the transmission of the signal which it emits during a break-in of the opening of the case, to erasure means 14. The control line 12 includes a voltage comparator 16 as well as a microcontroller 18. During a break-in detection, the detector 10 transmits a signal to the comparator 16 whose output changes logic state.

This change of state is first of all taken into account by the circuit 20 for energizing the microcontroller, which makes it possible to keep the latter de-energized in the absence of an event, that is to say either the composition of the code on the secret device 22 incorporated in the normal opening means 41, ie the detection of a break-in. This arrangement reduces the power consumption, insofar as only the comparator 16 is permanently energized.

The change of state of the comparator 16, induced by the signal emitted by the detector 10, is then taken into account at the level of an input 24 called "interruption" of the microcontroller 18 which then activates the triggering of the means of erasure 14, by closing the switch 6

(figure 3).

It should be noted that the command line 12 is able to react under the action of a signal emitted by means? detecting not only the break-in of the opening of the case, but also the break-in of the fixed walls of the case, or even the displacement of the case.

To detect attempts to pierce the fixed walls of the housing, these are covered by conductive wires 15 (FIG. 7) constituting a mesh network, and the detection means comprises an electronic circuit of known type detecting the variation in electronic resistance resulting from the breakage of at least one conductive wire. It will be recalled that the erasing means comprise a generator of direct or alternating current 9, which makes it possible to supply coils 81 and 82 so as to create two magnetic fields of identical polarities on either side of the floppy disk 30. The floppy disk 30 to be protected is arranged in the air gap of the coils 81 and 82. Thus, when the detector 10 detects an attempt to break into the housing, it emits a signal transmitted via the control line 12 to the erasing means 14. The latter then generate a magnetic field sufficiently strong to ensure the demagnetization of the information stored in the document 30, in two phases between which the polarities magnetic fields are reversed, making them impossible to read.

It is conceivable to replace the generator and the turns described above for any erasing device initiated during the breaking of the box, insofar as such a device allows the application on either side of the support, of two fields magnetic of the same polarity and of sufficient intensity towards the support to be protected.

Referring again to FIG. 6, the current generator 9 is supplied by an energy source constituted by an accumulator battery 7 which can be recharged from the mains by known means (see FIG. 5).

In this regard, recharging the accumulators 7 poses the problem of an attempt at sabotage by applying, from outside the housing, an electric voltage high enough to destroy the internal circuits of the housing 8 and thus prevent the triggering of the means erase 14.

A solution for preventing such an attempt at sabotage is explained by means of FIG. 7. As the latter shows, the regulation of the charge of the accumulators 7 is ensured by connectors 34 arranged on the external face of the wall 36 of the housing. 8 (on the left of FIG. 7), and electrically connected to the sector 38. In order to protect these connectors 34, the internal face of the wall 36 of the housing 8 (on the right of FIG. 7) is provided with a device 40 says "spark gap". This spark gap is 12

known type, for example gas capable of being ionized, enclosed in an enclosure, and placed electrically in parallel with a varistor. This device is calibrated by a determined voltage so that it prevents the application of a higher voltage at the internal circuits of the housing.

As shown in FIG. 8, another possibility of prevention against a possible sabotage consists in transmitting energy to the accumulators 7 via a magnetic circuit 42. The latter comprises an external transmitter winding 44 in relation to the sector 38 , as well as an internal receiver winding 46 in relation to the accumulators 7.

Thanks to such an installation, the magnetic circuit 42 and the housing 8 can be made electrically integral. In addition, by calculating as closely as possible the volume of the magnetic circuit 42, it is possible to limit the transfer of energy towards the accumulators 7, due to the saturation of the magnetic circuit 42. special case where the support to be protected is a card 43 called "chip", such as for example a bank card. In this case, the magnetic erasing means 14 can be replaced by electric erasing means 45. The latter include a generator 47 delivering an alternating voltage to a transformer 48 serving to raise the nominal voltage of the energy source, so that the assembly can render the chip 50 unusable by any reading system. The connection with the chip 50 of the card 43 is made by means of a connector 52 usually used for card reading applications.

Apart from the fact that the erasing means 45 are electric and no longer magnetic, the overall operation of the system is in accordance with that described above with reference to FIG. 6.

The invention is not limited to the examples described previously and various modifications can be made without departing from its scope.

Thus, it is possible to provide the device with protection against immersion. These are for example two electrodes connected to a second voltage comparator whose output changes state in the presence of a liquid in the housing, detected by the electrodes.

The change of state of the comparator is then taken into account by the microcontroller 18 which activates the erasing means 14 or 45, as described above.

The box according to the invention has variable dimensions depending on the number and size of the information carriers which must be housed there. Thus, we could be housed in a cubic box of about 15 centimeters on a side, up to 5 computer diskettes. In the particular case of storing a so-called "smart" card, the box has the approximate dimensions of an extra-flat pocket calculator.

According to particular applications, the device according to the invention can be integrated in a floppy drive or a hard disk drive, for example portable, and the protection against a reading in an unrecognized computer system, can be made by checking the exchanges data on the device connectors. The implementation of the invention in such a reader is easy for those skilled in the art and is therefore not more detailed here.

We also note that the number of coils depends on the distribution of the sectors into which the operating system divides the surface of the floppy disk.

Claims

1- Device for protecting data stored on a support (30) the content of which can be modified under the action of a magnetic field, comprising a housing (8) for housing said support, a detection means ( 10,15,16,18,20,22) emitting a detection signal during an unauthorized attempt to open the housing, erasing means (14) comprising a current generator (9) supplying turns ( 84) allowing the creation of a magnetic field in the vicinity of said support, the erasing means being adapted to cause said turns to pass through a current following the emission of said detection signal, in order to generate a magnetic field to erase computer data, characterized in that said turns are arranged on either side of the support and are adapted to jointly generate magnetic fields whose polarities are substantially identical on either side of said support. 2 - Device according to claim 1 characterized in that the erasing means are adapted to subject the support successively to magnetic fields of opposite polarities.

3 - Device according to any one of claims 1 or 2 characterized in that the support comprises a predetermined number of sectors (3), in that the turns are arranged in the form of coils (81,82) whose number is greater or equal to half the number of sectors. 4 - Device according to any one of claims 1 to 3 characterized in that the support has the shape of a disc, in that the turns are arranged in the form of a coil (81,82) have several magnetic pads (83) positioned radially with respect to the support, the radial dimension of the coils being greater than half the radius of the support.

5 - Device according to any one of Claims 1 to 4, the support comprising on the one hand a data area and on the other hand an identification and / or operating system area, characterized in that the magnetic field generated by the turns is liable to modify data in the memory area and data in the identification area and / or operating system.

6 - Device according to any one of claims 1 to 5 characterized in that the detection means (22) is connected to a normal opening system (41) of the housing and emits a detection signal when said opening attempt unauthorized takes place on said case opening system.

7 - Device according to any one of claims 1 to 6 characterized in that - the fixed walls of the housing are covered by conductive wires (15) constituting a mesh network,

- The detection means is an electronic circuit detecting the variation in electronic resistance resulting from the breakage of at least one conductive wire. 8 - Device according to any one of claims 1 to 7 characterized in that the current generator comprises a spark gap (40) connected to the internal face of the wall (36) of the housing (8).

9 - Device according to any one of claims 1 to 8 characterized in that the current generator comprises a magnetic saturation circuit (42) connected at its input to an energy source (9) and whose output is connected to the erasing means (14).

10 - Device according to any one of claims 1 to 9 characterized in that the housing (8) is portable and has a handle.