GB1605042A

GB1605042A - Secure information storage

Info

Publication number: GB1605042A
Application number: GB4464777A
Authority: GB
Original assignee: EMI Ltd
Current assignee: EMI Ltd
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1981-12-16

Description

(54) SECURE INFORMATION STORAGE (71) We EMI LIMITED, a British subject of Blyth Road, Hayes, Middlesex, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to secure material in which information is securely stored in a secure document.

Information is securely stored when the initially stored information can not be altered, easily or at all, to convey other information although erasure may be possible. When the secure document and stored information represent money or money's worth, as in a ticket, credit card, cash card or voucher, or represent a position, identity, authority or right such as an identity card, pass card, passport or key, there may be attempts to alter the information or replicate the information on an extra document for a fraudulent benefit.

There is therefore a need for an information storage medium in which the stored information is protected against alteration or misuse.

Magnetic tape is a very convenient record medium for secure documents as it is cheap and durable and the stored information is easily read out. However the stored information can very easily be altered. Techniques have been proposed such as magnetisable materials having very high coercivities, say 2000 oe or more, to make recording difficult without the use of special apparatus, eg US PS 3566356. Techniques have also been proposed, eg US PS 3946206, in which a magnetisable material layer is overlaid with a non-magnetic material layer of substantial thickness to make recording more difficult. In this way the non-magnetic layer spaces the magnetisable material from the record head, but, as described in US PS 3946206, head current can be increased, to a certain amount, to compensate for this and achieve recording. Furthermore a theoretical analysis related to typical practical cases, in Davies and Dudson (PROC IEE Reviews Vol.119, No.8R August 1975) at pp 958960, shows how to adjust head gap size and head gap field in terms of the spacing of the magnetisable material from the gap, saturation magnetisation of the head core material, the thickness of the magnetisable material and the coercivity of the medium. This analysis leads to the conclusion that even when magnetisable material is covered by a non-magnetic spacing layer it can be rewritten, at least at material coercivities up to several thousand oersteds and bit densities up to 100/inch, with suitably designed heads which are readily constructed. The need for a reliably secure information storage medium therefore still exists. An extremely secure storage medium is known, eg UK PS 1331604, in which the information is stored as the variation of the orientation of acicular magnetisable particles from point-to-point in a medium in which the particles are securely held. However while effective this technique requires that the information is incorporated during the deposition of a layer of magnetisable material when fluid in a settable binder, It is an object of the invention to provide a secure information store.

According to one aspect of the invention there is provided a secure store comprising a first layer of a magnetic material recorded in spaced, linear regions thereof to form a first pattern of magnetic flux transitions indicative of information or data, and a second layer of magnetic material, bonded to the first layer along its length and recorded, in spaced, linear regions thereof to form a second pattern of magnetic flux transitions which are inclined to the flux transitions in the first pattern, whereby application of a magnetic field to the bonded layers to change said first pattern so as to alter the information or data causes a change in said second pattern thereby indicating that said alteration has occurred.

The flux transitions in the two layers may be inclined at an angle of between 60 and 1200 and may preferably be aligned at an angle of between 80" and 110.

The materials in the two layers may have different coercivities. According to another aspect of the invention there is provided a method of making a secure store comprising the steps of providing a first layer of magnetic material magnetising said first layer in spaced linear regions thereof so as to generate a first pattern of magnetic flux transitions, providing a second layer of magnetic material and magnetising said second layer in spaced linear regions thereof so as to generate a second pattern of magnetic flux transitions, bonding said first and second layers together so that flux transitions forming said second pattern overlie, and are inclined to, flux transitions forming said first pattern.

The method may include providing said first and second layers on respective plastics material supports and bonding said supported layers together so that tie magnetic layers are sandwitched between the supports.

Embodiments of the invention will now be described with reference to the drawings accompanying the Provisional Specification in which, Figure 1 shows an apparatus for the construction of a secure information store and its incorporation in a secure document, Figure 2 shows a detail of a recording head in Figure 1 Figure 3 shows a detail of the document produced in the Figure 1 apparatus.

Figure 4 shows a secure document, in the form of a bank card, with the secure store and other magnetic tracks, Figure 5 shows the magnetisation format on the secure store, and Figure 6 shows in outline form an examination arrangement for a secure information store on a document as shown in Figure 3.

A plastics film, such as the proprietary material MYLAR (R.T.M.), is coated with a magnetisable material coating such as gamma iron oxide (yFe2O3) particles in a binder to produce a length of magnetic recording tape. Preferably the matenal, if anisotropic, is not aligned with the length of the tape, as is now conventional, for reasons explained below. Two rolls of the coated film recording tape are prepred, 11, 12, and placed on a feed assembly 10 with the magnetisable materials facing towards one another for eventual contact.

The tapes 111, 121 are fed through a common pinch roll assembly 13 in which the centre rolls 131, 132 are driven to revolve as shown by the arrows. The drive is arranged, eg by gearing together rolls 131, 132, so that the tapes move along together at the same speed and is a fixed superimposed relationship.

The tapes, 111, and 121 pass over a recording head assembly 141 including two head gaps and preferably also a reading head assembly 142 although this is not essential. The heads are connected to a source of data to be recorded as information securely stored in the finished document.

This source is exemplified by a printing telegraph machine 15, such as a teleprinter, which generates electrical impulse trains in accordance with key board selected alphanumeric characters. The impulses reach head 141 over wires 151. The pulses may be arranged in such a form that only part of the impulse train for a character reaches the head 141 to energise each gap. Clearly all parts of each impulse train must be used to energise one or other gap of head 141.

Head 141 is shown in outline in Figure 2.

The magnetic construction of the head can be conventional and is not described further. As mentioned above the head 141 has two magnetic recording gaps, indicated at 1411, 1412 respectively. on opposite faces.

These gaps, in one embodiment, are at an included angle of 90" to each other and both at 45" transversely of the axis along which the tapes 111, 121 pass through the apparatus. Other angles can be used, as will be apparent, to those skilled in the art, from the later description. The gaps can be energised from a common input signal to apply a similar recording flux pattern, albeit in different but complementary azimuth directions, or, as suggested above, different flux patterns each forming part of a character to be recorded. In the latter case separate magnetic circuits and energising coils are required. Pick up head 142 is similar to the construction adopted for head 141 but the signals from each gap are kept separate and fed to printing apparatus 15 to provide a check on the accuracy of the written information and a print out via machine 15, if required. Suitable pressure pads 143, 144 are provided to maintain tape/head contact.

A taper and pinchroll unit 16 brings the tapes together in the aforementioned magnetisable material contact. Care must be taken at this stage that the tapes retain the exact superimposed relationship existing at the recording head 141. To this end a taper guide 161 and pinch roll 162 are provided.

At this stage suitable plastics cards to carry the secure store are introduced. These may be the conventional pocket sized 54x85mm (21/8X33/8 in) cards, with suitable printing if required and also other magnetic record tracks in place if desired. The cards are placed in a card feeder unit 17. Cards from stack 175 are fed one-at-a-time down ramp 176 to gate 170 for controlled release into the entry pinch of laminator unit 18.

The gate 170 is operated to ensure a suitable spacing of the "blank" cards 171, 172, 173 on the tapes 111, 121.

The laminator 18 operates in conventional manner to laminate the superimposed tapes 111, 121 together and to the plastics card eg 172. A roller 181, heated, eg by radiant heater 182, exerts heat and pressure against roller 185. Rollers 184, 186 maintain the card and tapes in uniform motion. A cutter 187 enters a notch 188 to separate and trim the cards. The trimmed cards with the attached store collect in hopper 19.

If desired the binder of the magnetisable material can be formulated to be only completely set when heated in the laminator 18 and in this way the magnetisable material layers of the two tapes can be fused together against separation. Attempts to separate them will then destroy the layers.

Clearly some precautions are required to ensure that the recorded alignment is maintained during transfer and lamination and that the heat does not destroy magnetisation. However suitable techniques exist for card/tape lamination of the type described.

Figure 3 shows a scrap-section of the cards produced. The card "stock" is indicated at 179. The superimposed tapes 111 and 121 are cut-away to show the arrangement with the magnetisable material layers 1112, 1212 bonded together between the plastics layers 1111, 1211; the whole being forced into the card stock to produce a flush surface to the finished card, if this is desired.

More details of the magnetic arrangements will now be considered; as described above the secure store is formed by laminating together two tapes in magnetisable material contact after recording information on the tapes. Figure 4 shows a typical bank card with one of the accepted track formats, which will not be described further. Track 4, identified at T4, is the secure information store in this example. Clearly other areas and formats can be used. In particular the whole area prepared by laminating the tapes together need not be used for secure stor age. Part of the area can be erased and used for conventional erasable recordings. The erasure can be controlled to erase corrupted or superfluous parts of the securely stored information so that this information is more easily readable at an examination station without the need to select part of the information or ignore introductory data bits.

Figure 5 shows a typical magnetisation pattern. The magnetisation in one magnetis able material layer is in full line and in the other layer in dotted line. The magnetised areas (51 to 57 in one layer) have complementary areas (41-47) in the other layer.

The areas are at 90" to each other and each at 45" to the reading axis, AX, of the magnetic track. By using heads having appropriately aligned gaps the recorded information can be read out, and utilised as required, from each tape separately. When the same recording exists on each tape, the tapes being of similar material, a single gap, across the tape, can be used to check that balanced records exist.

The recorded information can be of any desired content. Thus if "personalised" cards are required, e.g. an individual pass card, the information can be applied at a point of issue. Alternatively, or in addition, the recorded information can represent money or money's worth, e.g. a stored value travel ticket or a voucher for, say, meals for one week in a hostel. Pensions and similar benefits can also be paid by using a stored value card. In particular when the recorded information represents a value to be used up piece-by-piece the stored information can be erased piece-by-piece to indicate the use.

The area 5 in Figure 5 represents such erasure. If required the tapes 111, 121 can incorporate a permanent magnetically detectable structure such as is disclosed in UK PS 1331604. The pressure of the structure can be checked for in the erased area 5.

Preferably this structure is aligned to not affect the signal read out from the stored information, e.g. placed across or along the tape axis.

The angles at which the recordings such as 41-47 and 51-57 are placed can be adjusted if required. To avoid cross-talk problems which increase signal processing complexity the included angle is preferably 90" + 10 although an included angle in the range of 60 to 1200 is clearly feasible and a wider range of included angle is not excluded by this specification of particular values. In general however a layout symmetrical with respect to the axis AX (Figure 4) is convenient.

The material in the tape can be randomly oriented or oriented to the respective gap direction, e.g. 45". The effects of using different combinations of gap direction and material orientation will be apparent to those skilled in the art.

The store provides security in that the information or components thereof is written independently on to each tape using a head in contact with the magnetisable material. Therefore once the tapes have been laminated together this type of writing is no longer possible. Accordingly attempts to modify the information stored on a finished card or other store carrier or copy it onto another carrier will not readily produce a recording of identical form due to the presence of the plastics spacing films such as 1211 or 1111 and 179. Furthermore, the "crossing" of the recordings, after they have been made on individual layers, and the superimposed layers, make it difficult to record on onl one layer in one direction without also affecting the other layer, which is then likely to also carry the recording.

The presence of substantially coincident but different field patterns in a genuine article thus provides a security feature.

If different coercivity materials are used then different recording intensities can be applied at unit 14 (Figure 1) to produce similar remanent magnetisation and thus a similar signal from a read head. Once the materials are bonded into contact such discrimination in recording intensity is not possible and a similarity of output will not be achievable.

The addition of a further layer of magnetisable material so that it lies between material layer 1112 and plastics layer 1111, or even between layer 1111 and stock 179, and providing a permanent magnetic structure in this further layer will assist in reducing the success of attempts to record on the finished store as such attempts will almost certainly "develop" the permanent structure. This is detectable on examination and can only be made undetectable by erasure which will erase the securely stored information as well. The further layer material coercivity and position are chosen to ensure that it is not "developed" during the production of the store.

As the secure store is formed from two magnetisable layers it is possible to introduce other secure material techniques into one or both layers. For example one layer may be produced as described in cognate UK patent applications 50846/76 and 30720/ 77 Serial no 1594940 (Serial No 1594940) to have an eye visible pattern and have the other layer at least partly overlaid to provide "crossed" magnetic recordings. The securely stored information may be used as an algorithm for encoding information on conventional recording tracks and modified at each use, by erasure, to resist "buffering" actions.

A typical reading and examining head configuration is shown in Figure 6. Conventional read/write/erase heads RWE0 to RWE 3 are provided for tracks 0 to 3. Two suitably inclined read-heads R1, R2 are provided for track T4 and a straight, E, or chevron, E', erase head. An auxiliary head A may be used for checking record balance.

The techniques described above provide for the secure storage of information with information is not easily alterable, if at all, except by erasure. Such erasure may be selective to be effected in stages with use of the card carrying the information.

WHAT WE CLAIM IS: 1. A secure store comprising a first layer of a magnetic material recorded in spaced, linear regions thereof to form a first pattern of magnetic flux transitions indicative of information or data, and a second layer of magnetic material, bonded to the first layer along its length and recorded, in spaced, linear regions thereof to form a second pattern of magnetic flux transitions which are inclined to the flux transitions in the first pattern, whereby application of a magnetic field to the bonded layers to change said first pattern so as to alter the information or data causes a change in said second pattern thereby indicating that said alteration has occurred.

2. A secure store according to Claim 1 wherein the flux transitions in the two layers are inclined at an angle of between 60 and 120 .

3. A secure store according to Claim 2 wherein the flux transitions in the two layers are inclined at an angle of between 80" and 110 .

4. A secure store according to any one of claims 1 to 3 wherein the materials in the two layers have different coercivities.

5. A secure store according to any one of claims 1 to 4 wherein the first layer is comprised of anisotropic magnetic particles, particles in distinct, spaced regions of the layer being aligned along a first direction and particles in others than said distinct, spaced regions being either unaligned or aligned along a substantially different direction.

6. A secure store according to Claim 5 wherein the first layer is formed of y ferric oxide.

7. A secure store according to any one of Claims 1 to 6 comprising a length of plastics material bonded to the outwardly facing sides of said first and second layers.

8. A secure store according to Claim 7 including a further layer of magnetic material disposed between the said first layer and the overlying plastics material layer.

9. A method of making a secure store comprising, the steps of providing a first layer of magnetic material magnetising said first layer in spaced linear regions thereof so as to generate a first pattern of magnetic flux transitions, providing a second layer of magnetic material and magnetising said second layer in spaced linear regions thereof so as to generate a second pattern of magnetic flux transitions, bonding said first and second layers together so that flux transitions forming said second pattern overlie, and are inclined to, flux transitions forming said first pattern.

10. A method according to Claim 9 including providing said first and second

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. recording of identical form due to the presence of the plastics spacing films such as 1211 or 1111 and 179. Furthermore, the "crossing" of the recordings, after they have been made on individual layers, and the superimposed layers, make it difficult to record on onl one layer in one direction without also affecting the other layer, which is then likely to also carry the recording. The presence of substantially coincident but different field patterns in a genuine article thus provides a security feature. If different coercivity materials are used then different recording intensities can be applied at unit 14 (Figure 1) to produce similar remanent magnetisation and thus a similar signal from a read head. Once the materials are bonded into contact such discrimination in recording intensity is not possible and a similarity of output will not be achievable. The addition of a further layer of magnetisable material so that it lies between material layer 1112 and plastics layer 1111, or even between layer 1111 and stock 179, and providing a permanent magnetic structure in this further layer will assist in reducing the success of attempts to record on the finished store as such attempts will almost certainly "develop" the permanent structure. This is detectable on examination and can only be made undetectable by erasure which will erase the securely stored information as well. The further layer material coercivity and position are chosen to ensure that it is not "developed" during the production of the store. As the secure store is formed from two magnetisable layers it is possible to introduce other secure material techniques into one or both layers. For example one layer may be produced as described in cognate UK patent applications 50846/76 and 30720/ 77 Serial no 1594940 (Serial No 1594940) to have an eye visible pattern and have the other layer at least partly overlaid to provide "crossed" magnetic recordings. The securely stored information may be used as an algorithm for encoding information on conventional recording tracks and modified at each use, by erasure, to resist "buffering" actions. A typical reading and examining head configuration is shown in Figure 6. Conventional read/write/erase heads RWE0 to RWE 3 are provided for tracks 0 to 3. Two suitably inclined read-heads R1, R2 are provided for track T4 and a straight, E, or chevron, E', erase head. An auxiliary head A may be used for checking record balance. The techniques described above provide for the secure storage of information with information is not easily alterable, if at all, except by erasure. Such erasure may be selective to be effected in stages with use of the card carrying the information. WHAT WE CLAIM IS:

1. A secure store comprising a first layer of a magnetic material recorded in spaced, linear regions thereof to form a first pattern of magnetic flux transitions indicative of information or data, and a second layer of magnetic material, bonded to the first layer along its length and recorded, in spaced, linear regions thereof to form a second pattern of magnetic flux transitions which are inclined to the flux transitions in the first pattern, whereby application of a magnetic field to the bonded layers to change said first pattern so as to alter the information or data causes a change in said second pattern thereby indicating that said alteration has occurred.

10. A method according to Claim 9 including providing said first and second

layers on respective plastics material supports and bonding said supported layers together so that the magnetic layers are sandwitched between the supports.

11. A method according to Claims 10 or 11 including attaching the bonded layers to a carrier comprised of a card or sheet of a plastics or paper material to form a security document.

12. A method according to any one of Claims 9 to 11 wherein the said first and second layers are magnetised and bonded so that their respective flux transitions are inclined to one another at an angle of between 60 and 1200.

13. A method according to Claim 12 wherein said flux transitions are inclined at an angle of between 80" and 110 .

14. A security document including a secure store according to any one of Claims 1 to 8, bonded to a carrier of card or sheet form made of a plastics material or paper.

15. A security system including at least one security document according to Claim 14, a read head for detecting magnetic flux transitions, and a write head for rerecording said layer to erase one or more flux transitions.

16. A method of making a secure store substantially as hereinbefore, described by reference to Figures 1 and 2 of the drawings accompanying the Provisional Specification.

17. A secure store substantially as hereinbefore described with reference to Figures 3, 4, 5, and 6 of the drawings accompanying the Provisional Specification.