METHOD AND APPARATUS FOR AUTHENTICATING MEMORY DISK

Abstract: A technique for enabling authentication of a magnetic memory disk. Predetermined portions of preselected tracks on the disk recording surface are deliberately removed and the locations of the modified portions are recorded, along with an initial program routine. The portions are alterna­ tively removed by mechanically abrading the recording sur­ face using a stylus, by embossing the preselected portions and applying an abrasive member to the embossed raised surfaces, by burning off the portions with a laser, or by chemical etching. When the disk is inserted into a drive, an initial program routine recorded on the disk causes the drive transducer to seek the pretreated portions and at­ tempt a write and subsequent read operation. A successful write/read operation indicates a counterfeit copy. This in­ dication may be used to signal the operator or erase the en­ tire program from the disk.

Description: METHOD AND APPARATUS FOR AUTHENTICATING MEMORY DISK Background of the Invention This invention relates to the storage of information on magnetic media, and particularly to techniques for checking the authenticity of such media. In the field of data processing, thousands of computer programs have been developed and sold and this proliferation is expected to continue. Many programs are currently being marketed in the form of digital information stored on flexible or "floppy" disks. Typically, once an original program has been created and recorded on a master, copies of the program are made by recording from the master onto initially blank floppy disks, which are then sold to the trade. Due to the ease with which unauthorized or "bootleg" copies can be made from a legitimate copy of the program, many techniques have been proposed to render the production of such unauthorized copies difficult. One such general technique on which much effort has been expended is the encryption of the program itself. The encryption technique is usually implemented by recording some secret predetermined sequence of bits of information somewhere on the disk and providing an encryption key in the computer with which a particular program will be used, so that the computer will refuse to recognize a copy of the program unless the encryption code matches the encryption key stored in the computer. In spite of numerous clever encryption codes employed, the encryption technique in general has not been an effective deterrent to the production of bootleg copies since clever programmers seem capable of breaking the code. In addition, the encryption technique suffers from the disadvantage that it is not universally applicable to all computers, particularly computers in which the controller for the disk drive on which the flexible disk is operated is a portion of the drive itself and not a portion of the software Summary of the Invention The invention comprises a method and apparatus for enabling the authentication of a magnetic disk which is universally applicable to all computer systems, is relatively simple to implement and exceedingly difficult to defeat. From a method standpoint, the invention comprises the deliberate destruction, during manufacture, of a predetermined portion of the recording surface of the disk so that the disk can be automatically checked by the computer for authenticity as an initial step in the use of the program. For disk media, the predetermined portion of the recording surface which is deliberately destroyed is preferably part of one or more sectors of one or more tracks on the disk. Destruction of the predetermined portions of the recording surface is accomplished in one of several alternate ways: mechanical abrading using a pointed stylus, burning off using a laser beam, embossing the predetermined portions and then mechanically abrading the embossed portion, or chemically etching the predetermined portions. When making the legitimate copy of the program, the locations of the removed portions (i.e track and sector numbers) are recorded as part of the computer program. The recording characteristics of the remainder of the recording surface remain substantially unaffected by the removal process. Also recorded as part of the program is an initial routine for checking the recording integrity of those predetermined portions which have been altered. When a legitimate copy of the program is inserted into a drive for use with the associated computer, the initial part of the program requires the computer system to operate the disk drive in such a manner as to position the read/write transducer over the one or more locations where the predetermined portions of the recording surface have been removed. Next, an attempt is made to write data onto each location and to read data back from such location. For a legitimate copy of the program, it will be impossible to perform a successful write and read operation from any one of these locations, since the magnetic recording layer was removed when the copy was prepared. For bootleg copies, however, a successful write/read operation will be performed. Accordingly, if a successful write/read operation is detected, the program recorded on the disk requires that the computer abort any further operation with that disk. In addition, if desired the program may instruct the computer to erase the information recorded on the entire disk surface. In order to avoid the inadvertent abort of operations with a legitimate copy due to the reading of random noise, a special pattern of random data blocks is used during the write/read attempt on each removed portion, and any data read from such portions is matched against this random data block. In the event of a match, the copy is illegitimate and the abort procedure is followed. From an apparatus standpoint, a preferred embodiment of the invention for use with flexible disks includes a stylus member mounted on a translatable disk drive arm immediately adjacent one surface of the disk, when mounted on a centrally located drive spindle, and a mechanical biasing mechanism reciprocally mounted adjacent the reverse surface of the disk for biasing the disk from the reverse side against the tip of the stylus, when actuated. Preferably, the biasing mechanism includes a bearing wheel rotatably mounted on the yoke end of a solenoid actuated rod, and a spring member for normally biasing the bearing wheel away from the reverse surface of the disk. For a fuller understanding of the nature and advantages of the invention, reference should be had to the ensuing detailed description taken in conjunction with the accompanying drawings. Brief Description of the Drawings Fig 1 is a schematic side view illustrating a preferred embodiment of the apparatus; Fig 2 is a front perspective view, partially broken away, of the apparatus of Fig. 1; Fig. 3 is an enlarged elevational view, partially in section, showing the stylus and stylus housing; Fig. 4 is an enlarged sectional schematic view illustrating operation of the apparatus of Fig 1; and Fig. 5 is a flow chart showing the authentication routine. Description of the Preferred Embodiments Turning now to the drawings, Figs. 1-4 illustrate a preferred embodiment of the apparatus for preparing the disk recording surface, and which is specifically designed for use with flexible disks. As is well known to those skilled in the art, flexible disks comprise a substrate of a durable resilient material, such as Mylar material, on one or both surfaces of which a magnetic recording layer is adhered. The thickness of the Mylar substrate is typically in the range from three to ten mils., while the thickness of the recording layer is typically in the range from one hundred to five hundred microinches. Such disks are designed to record bits of information in concentric circular tracks which are typically recorded with a width in the range from six to twelve mils., the spacing between adjacent tracks being on the order of one-half the track width. The disk per se is encased in a protective jacket in such a manner that the disk can be rotated inside the jacket when the disk is received on the hub of a rotatable spindle mounted in the disk drive. As shown in Fig. 1, the apparatus includes an arm 11 driven by a motor 12 in opposite radial directions (designated by arrow 13) with respect to a flexible disk 15 mounted on a hub 16. The hub 16 is arranged to be rotated in the direction indicated by arrow 17 by means of a shaft 18 driven by a second motor (not shown). The flexible disk 15 includes the compound substrate/recording layers generally designated by reference numeral 20, and a jacket 24 shown partially broken away. Motor 12 may comprise any one of a number of known drive motors used to translate flexible disk drive transducer arms radially of the disk. Arm 11 is a modified version of a standard flexible disk drive transducer arm and includes a bottom reference surface 31 on which a stylus assembly 40 is secured, e.g. by bonding with an epoxy adhesive. With reference to Fig. 3, stylus assembly 40 includes a stylus member 41 having a flatted shaft portion 42 and a cutting tip 43. Stylus member 41 is mounted in a central aperture of a stylus mounting member 44, the central aperture having a narrow upper portion 45 and a threaded counter bored portion 46 in which an adjustment screw 47 is received. Stylus mounting member 44 also has a threaded lateral bore 49 in which a stop screw 50 is received for the purpose of fixing the axial position of stylus member 41. The upper surface of stylus mounting member 44 has a partially spherical recess 51 into which the cutting tip 43 of stylus 41 extends. The radius of curvature of recess 51 is preferably 0.25 inch for a diamond tipped Phonopoint stylus with a length of 0.38 inch and a diameter of 0.081 inch. The stylus 41 is installed in the stylus mounting member 44 by inserting the stylus in to the upper central bore 45, adjusting the height of the stylus so that the cutting tip extends 0.001 inch into the recess by adjusting the adjustment screw 47, after which the stop screw 50 is adjusted to provide mating engagement with the flatted surface 42. With reference to Figs. 1 and 2, secured to a raised mounting pedestal portion 55 of lower arm 11 is a mechanical biasing mechanism which includes a lower mounting block 57 secured to pedestal 55 by means of a pair of mounting screws 58, 59, to which a u-shaped cover member 60 is secured by means of mounting screws 61, 62. Secured approximately midway of cover member 60 is an upper mounting block 65 in the shape of an inverted "L", to the upper surface of which a conventional electromechanical solenoid 66 is mounted by means of a mounting bracket 67 and a pair of mounting screws 68, 69. At the inner free end of cover member 60 a threaded bushing member 71 is received in an aperture 72 and secured by means of threaded nut 73. Slidably received within a central aperture 74 of bushing 71 is a shaft 76 having a bearing yoke 77 secured to the bottom thereof by means of mounting screw 78. A wheel bearing shaft 80 is carried by the bearing yoke 77 and maintained in place by a pair of conventional clips (only one 81 of which is shown - see Fig. 2). A bearing wheel 83 is rotatably received on pin 80 and is centralized by means of a pair of annular spacers 84, 85. Shaft 76 is normally biased upwardly as viewed in Figs. 1 and 2 by means of a bias spring 88 which bears against bushing 71 and a retainer ring 89 received in a slot 90 formed in the upper periphery of shaft 76. In order to prevent rotation of shaft 76 about the longitudinal axis during translational movement, bushing 71 is provided with a keyway 92 and the lower end of shaft 76 is provided with a radially extending guide pin 93 which slides in the keyway 92. Mounted in a bore 95 in an overhanging portion of upper mounting block 65 are a pair of cup shaped spring guides 96, 97 arranged in facing relation with a bias spring 99 located in the cup recesses to bias spring guides 96, 97 in opposite directions in bore 95. The upper end of shaft 76 bears against the lower surface of lower spring guide 97. The lower end of solenoid plunger 101 bears against the upper surface of upper spring guide 96. In operation, when solenoid 66 is actuated by an appropriate signal, shaft 76 is biased downwardly by means of the force translated from the solenoid plunger 101 through upper spring guide 96, intermediate spring 99 and lower spring guide 97 against the restoring force provided by reverse bias spring 88. When shaft 76 is translated downwardly, wheel bearing 83 presses against the upper surface 103 of the flexible disk 20 (see Fig. 4) causing the lower recording surface 104 to press against the forward cutting edge 106 of the stylus 41. By timing the actuation of solenoid 66 in conjunction with the operation of motor 12, any preselected portion of any given track on the disk 15 can be cut away by the apparatus shown in Figs. 1-4. The depth of penetration of the cutting edge 106 of stylus 41 is limited by the vertical adjustment of stylus 41 in the recess 51 of the stylus mounting member 44, and should be such that the cutting edge 106 actually penetrates through the lower recording surface layer partially into the substrate 105. The actual amount of the extension of the cutting edge 106 above the termination of the cylindrical bore 45 depends upon the thickness of the recording layer 104 to be removed. Typically, the range of thicknesses encountered is from one hundred to five hundred microinches. The length of the amount of recording surface 104 material to be removed from a given track is a choice of the designer and typically should be several bytes in length. Since the length of a byte is dependent upon several factors, including recording density, track formatting and the like, this parameter may best be empirically selected. For a disk formatted with 256 bytes per sector, a length equal to 50 bytes, for example, may be removed which requires removal of approximately one quarter inch of the lower recording layer 104 from that particular track sector. Once a disk 15 has been treated with the apparatus of Figs. 1-4 at one or more locations, these locations can then be recorded onto undisturbed portions of the same track or other tracks along with the computer program (or other data) which incorporates the initial routine illustrated in the flow chart of Fig. 5. With reference to Fig. 5, once a disk having the program with the initial routine shown in this figure is inserted into a disk drive for use, the initial portion of the program stored on the disk 15 will cause the following sequence of events to take place. After the start step, the routine checks to determine whether the disk is write protected. If the disk is write protected, the program jumps to the return bad flag operation (since it is presumed that a legitimate copy is not write protected). Next, the computer instructs the read/write transducer arm motor to translate the transducer to the first track having a deleted recording surface portion. Once the transducer has been radially translated to that track, the write/ read electronic circuitry in the disk drive is instructed to write a random data block of information to the predetermined sector of that track. Thereafter, the read/write circuitry in the disk drive is instructed to attempt a read from the same sector of that track. The data recovered as a consequence of the read error is checked to determine whether a read error was obtained. If no read error is detected, the disk is an illegitimate copy and the program steps to the return bad flag state. If a read error is obtained, then the first bytes of data are checked against the random data block which was generated prior to writing that random data block onto the predetermined sector. If a match is not obtained, the program steps to the return bad flag state. If a match is obtained, signifying that information was truly written to the disk the program steps to the return good flag state, which signifies a legitimate copy is located in the disk drive. The return bad flag state may be used in a number of ways. For example, this flag may be used to simply abort any further operation of the computer until the disk is removed from the drive. Alternatively, the return bad flag state may be used to initiate a total erase operation in which the disk drive transducer is progressively stepped across the recording surface and operated in an erase mode. the return bad flag condition may also be used to activate a visible display, an alarm buzzer or the like. while the preferred embodiment of the apparatus for use with flexible disks is that illustrated in Figs. 1-4, other equivalent apparatus may be used to prepare the disk for subsequent authentication. For example, the mechanical abrading technique may be modified by providing suitable apparatus for embossing predetermined portions of predetermined tracks by arranging the flexible disk 20 on a suitable stamping dye having raised circular segments and pressing a mating dye having mating circular segmental recesses against the first dye. After embossing, the recording surface can then be burnished with a flat burnishing surface to abrade away the raised embossed recording surface layer portions. Alternatively, a laser having a suitable beam width may be operated in a manner essentially similar to the solenoid to burn off the preselected portions of preselected tracks of the recording surface. In addition, the predetermined portions may be removed chemically using conventional photolithography techniques, e.g. providing a suitable mask having the desired removal pattern, applying a layer of photo resist material over the recording surface, installing the mask over the photo resist layer, exposing the mask to suitable radiation, etching away the appropriate underlying portions of the recording surface layer and stripping off the photo resist material. The actual number of damaged recording surface layer portions and the location thereof may be selected by the designer in an empirical fashion. Generally speaking, the invention is most effective when several portions are removed at random locations which may vary from specific program to specific program or even between different copies of the same program. Enhanced protection for authentic copies may be obtained by recording key portions of the computer program on tracks which flank the tracks having the removed recording layer portions and on the same track on sectors which immediately precede and follow the damaged track portion. The timing circuitry necessary to position the recording surface removal equipment over the proper track and to operate the solenoid (or fire the laser) is conventional circuitry which forms no part of the invention. In general, the index hole provided in each flexible disk provides a circumferential starting reference pulse in conventional systems, which have suitable counting circuitry for delineating bit cell positions, byte length and sector length. while the above provides a full and complete disclosure of the invention, various modifications, alternate constructions and equivalents may be employed without departing from the spirit and scope of the invention. For example, although the invention has be described with reference to flexible disks, it is equally applicable to rigid disks as well. In#addition, while specific reference has been made to disks having a computer program stored thereon, the invention can be employed with disks having other pre-recorded information, such as a data base. Therefore, the above should not be construed as limiting the invention, which is defined by the appended claims.

Claims: CLAIMS: 1. A method for enabling authentication of a magnetic storage device, said method comprising the steps of: (a) providing a magnetic storage device (15) having a recording region (104); and characterized by: (b) modifying a predetermined portion of said region (104) so as to remove the recording property, while leaving the recording property of the remainder of said region (104) substantially unaffected. 2. A method for enabling authentication of a magnetic storage device, said method comprising the steps of: (a) providing a magnetic storage device (15) having a recording surface (104); and characterized by: (b) removing a predetermined portion of said recording surface (104) while leaving the recording property of the remainder of said recording surface (104) substantially unaffected. 3. The method of claim 2 wherein said magnetic storage device (15) comprises a disk (20) having a flexible substrate (105) on which said recording surface (104) is supported, and characterised in that said predetermined portion removed in accordance with step (b) comprises a circular segment corresponding to a portion of a data track. 4. The method of claim 2 characterized in that said step (b) of removing includes the step of mechanically abrading away said predetermined portion. 5. The method of claim 2 characterized in that said step (b) of removing includes the step of chemically dissolving said predetermined portion. 6. The method of claim 2 characterized in that said step (b) of removing includes the step of burning off said predetermined portion with a laser. 7. The method of claim 2 characterized in that said step (b) of removing includes the steps of (i) embossing said predetermined portion of said recording surface (104), and (ii) abrading away said embossed predetermined portion. 8. The method of any one of claims to 7 further characterized by the step of (c) recording on said magnetic storage device (15) the location at which the predetermined portion of said recording surface was removed. 9. A method for detecting an unauthorized copy of a magnetic storage device (15) having a recording surface (104,105), said method being characterized by the steps of: (a) positioning a read/write transducer over a predetermined normally defective portion of said recording surface (104,105); (b) operating said transducer in a write mode to attempt to record information on said predetermined portion; (c) operating said transducer in a read mode to attempt to read any information recorded on said predetermined portion; and (d) determining whether steps (b) and (c) resulted in the successful recording of said information on said predetermined portion to indicat that the magnetic storage device (15) is an unauthorized copy. 10. The method of claim 9 characterized in that said magnetic storage device (15) has recorded thereon the location of said normally defective predetermined portion, and wherein said step (a) of positioning is preceded by the step of reading the location information from said magnetic storage device (15). 11. The method of claim 9 or claim 10 characterized in that said information comprises a predetermined sequence of bits of information, and wherein said step (d) includes the step of comparing any information read from said predetermined portion with said predetermined sequence of bits of information. 12. An apparatus for modifying the recording surface (104) of a magnetic storage device (15), said apparatus being characterized by: means (16,18) for translating a portion of said recording surface (104) past a work station, and means (40) at said work station for removing said portion of said recording surface (104) while leaving substantially unaffected the recording properties of the remainder of said recording surface (104). 13. The apparatus of claim 12 characterized in that said magnetic storage device (15) is a disk (20) having a substrate (105) on which said recording surface (104) is located; wherein said translating means includes a rotatable spindle (16,18) for supporting said disk; and wherein said removing means includes a stylus member (41) engageable with said recording surface (104) for abrading said portion therefrom. 14. The apparatus of claim 12 or claim 13 characterized in that said disk substrate (105) is flexible; wherein said stylus (41) is securely supported adjacent said recording surface (104); and wherein said removing means further includes a mechanical bias member (83) reciprocably mounted on the opposite side (103) of said recording surface from said stylus (41) for biasing said substrate (105) toward said stylus member (41) to provide abrading contact between said stylus member (41) and said portion of said recording surface (104). 15. The apparatus of any one of claims 12 to 14 characterized in that said stylus member (41) is securely mounted in a housing (44) having a central relieved portion, and wherein said stylus member terminates in a cutting tip terminating in said recessed portion (51).

Inventors: JURACICH, JOHN GERALD, WINKLER, JAMES LEAIRD
Applicants: DYSAN CORPORATION
Application year: 1983
Main classification: G11B23
IPC codes: G11B19, G11B23, G11B5, G11B33, G11B20