Abstract:
A system and method are described for rendering Compact Discs (CDs) and Digital Video Discs (DVDs) unreadable. Embodiments comprise a frame, a guide for constraining motion of the frame with respect to a disc, and at least one scraping element. Scraping elements may be positioned to damage the disc volume descriptor while the frame moves in a constrained manner relative to the disc. The guide may comprise a spindle which engages the center hole of a disc to hold the frame in a radially-fixed position. A scraping element on the frame damages the disc as the disc rotates relative to the frame. The guide may be integrated, such that the frame comprises a slot through which the disc passes. A scraping element inside the slot damages a disc as it passes through. Embodiments are hand operated, not motorized, and some have no moving parts. Embodiments also function with non-optical media.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a divisional of U.S. patent application Ser. No. 11/450,751, filed Jun. 9, 2006, titled “System and Method for Disposal of Digital Media”, and claims priority thereto. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates generally to computer security devices, and more specifically to devices for destruction of computer-readable media. 
       BACKGROUND OF THE INVENTION 
       [0003]    Disposal of intact Compact Discs (CDs) and Digital Video Discs (DVDs), including CD-Rs, CD-RWs, DVD-Rs and DVD-RWs, risks disclosure of information contained on the media, similar to the risks faced during disposal of intact paper documents. The paper security problem has been largely addressed, with the widespread availability of relatively inexpensive paper shredders for home, business and industrial environments. However, an equivalently reliable and cost-effective solution for rendering discs unreadable is not in widespread use. 
         [0004]    As CD and DVD writers are becoming more affordable, there is an increase in the use of these types of discs for storage of confidential information. Businesses store trade secrets and personal information that is subject to privacy restrictions. Home users often write financial data and highly personal information on CDs and DVDs. If these are placed in the trash in an intact state, the confidential information may then be read by anyone who removes the discs from the trash. 
         [0005]    Common methods to render a disc unreadable include burning, pulverizing, shattering, snapping, grinding and scratching the label side of the disc into the data layer. Burning and pulverizing may be quite effective in rendering a disc unreadable. Unfortunately, those methods may require expensive equipment. Shattering and snapping can be difficult for people without either the required strength or tools. Additionally, shattering or snapping a disc presents a risk of injury from sharp, flying shards. Multiple models of disc grinders are available, although their size, cost and requirement for electric power may limit their desirability for certain potential users. 
         [0006]    Scratching into the data layer can often be done easily with any sharp instrument. However, it presents risks, including injury and unintentional damage to other surfaces. Further, the damage to the disc may not be complete enough to render a disc unreadable. One reason that scratching a disc may not be adequate is that a typical disc user may not be aware of the physical layout of the data on a CD or DVD surface, and therefore may not sufficiently damage the critical data areas. 
         [0007]    A CD typically contains a volume descriptor in sector  16 , which is within a fraction of an inch of the innermost portion of the optically-readable section of the disc. Disc readers typically first read the volume descriptor, also known as an index, to determine the contents of the disc. If this section is damaged or missing, the majority of disc readers may be unable to read the disc. However, due to its small size and its location near the innermost part of the optically-readable area, it is easy to miss with uncontrolled, random scratching. A disc with an intact volume descriptor may still be readable, and files whose data area has not been adequately damaged may be fully recoverable. Therefore, simply scratching a disc randomly with a sharp instrument does not provide safe, quality-controlled destruction. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    Embodiments of the invention allow for a reliably consistent level of damage by guiding a scraping element across at least one predetermined area of a disc, such as the volume descriptor. Embodiments of the invention require no motors and may have no moving parts. That is, some embodiments of the invention may be rigid devices that move as a single unit relative to a disc, while holding at least one scraping element that scrapes the disc during the motion. Some embodiments, however, may comprise flexible scraping element(s) that flex or partially retract into cavities in response to pressure from a disc against the scraping elements. Relative motion may be rotational, straight across, or even curved, resulting in one or more scraping paths that form arced, straight, waved, looped lines or a combination thereof. 
         [0009]    The relative positions allowed between a scraping element and a disc may be constrained such that relative motion between the scraping element and the disc is constrained for at least part of the motion. The relative motion between a scraping element and a disc may be constrained by using a guide to constrain relative motion between the disc and a frame that holds the scraping element. The constraint may serve to align the disc with the scraping element(s). Embodiments of the invention allow for multiple types of guides, including a spindle that engages the center hole of a disc and allows only rotational motion. The spindle holds the frame in a radially-fixed position, such that a scraping element moves in an arced scraping path at a predefined radius. The radius of the scraping path may correspond to the radius at which the volume descriptor may be found, or any other part of a disc targeted for damage. 
         [0010]    Embodiments of the invention may also comprise at least one guide that protrudes from the frame to abut the edge of a disc. Such a guide may constrain the relative position of the frame when the frame spans a disc at its widest point. Since the position of the guide may be fixed relative to the frame, and the position of a scraping element may also be fixed relative to the frame, the position of the scraping element may then be fixed relative to the edge of the disc. A pressure element may be provided, which holds a disc against the scraping elements. In some embodiments, guides that abut opposing edges of a disc may form a rectangular slot along with a pressure element and a frame holding the scraping elements. A disc passing through the slot will then have its motion constrained by the inner dimensions of the slot. Scraping elements on both the frame and the pressure element can ensure that both sides of a disc are damaged. 
         [0011]    Embodiments of the invention may comprise multiple scraping elements to provide multiple scraping paths. A certain number of paths may be desired to achieve a particular level of damage, such that the data area sustains damage at some desired density. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
           [0013]      FIG. 1  shows an embodiment of the invention; 
           [0014]      FIG. 2  shows damage done to a disc by the embodiment of  FIG. 1 ; 
           [0015]      FIG. 3  shows another embodiment of the invention; 
           [0016]      FIG. 4  shows damage done to a disc by the embodiment of  FIG. 3 ; 
           [0017]      FIG. 5  shows options for various embodiments of the invention; 
           [0018]      FIG. 6  shows a method for using an embodiment of the invention; and 
           [0019]      FIG. 7  shows a method for using an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    In many situations, it may only be necessary to destroy a disc&#39;s volume descriptor, or file index, in order to provide the desired level of destruction. In other situations, destroying both the file index and a portion of the data area, leaving other portions of the data area untouched, may suffice. That is, it may not be necessary to render a disc entirely unreadable by all equipment, in order to achieve a security goal. Some equipment and software is available to enable reading a disc with a damaged volume descriptor and rebuilding much of the disc&#39;s content. However, not every disposal situation requires addressing the threat posed by such equipment and software. Rather, based on the data density and locations of data on a disc, a number of scraping elements may be provided to ensure that specific locations or a minimum percentage of the disc surface is damaged. 
         [0021]      FIG. 1  shows disc scraper  10 , comprising frame  100  and spindle  101  that engages the center hole of a disc. Spindle  101  protrudes sufficiently beyond any other protrusions from the frame in order to pass through the disc&#39;s hole, and is sized to fit the hole. When a disc is placed over spindle  101 , frame  100  may rotate with respect to the disc, but cannot move radially with respect to the disc. That is, while the frame is in a radially-fixed position with respect to the disc, either the disc or the frame may rotate, or both. Spindle  101  should be sized to limit lateral movement between a disc and the frame, but should not be so tight in the disc that it causes unnecessary drag during rotation. 
         [0022]    Scraping elements  102   a  and  102   b  are positioned between  21  and  23  millimeters (mm) from the center axis of spindle  101 , in order to scrape the volume descriptor. If scraping elements  102   a  and  102   b  are opposite the center axis of spindle  101  from each other, then rotating the frame only half a circle will trace an entire circle on the disc, scraping the entire volume descriptor. Operation of scraper  10  requires a user to press a disc by hand, or another suitable method, against scraper  10  and rotate the disc and scraper  10  relative to each other. 
         [0023]    Scraping elements  103   a - d  are positioned further than 25 mm from the center axis of spindle  101 , in order to damage the data area of a disc outside the volume descriptor. Any number of scraping elements may be used, based on the desired scratching or scraping density and the width of each scraping element. Scraping elements  102   a  and b and  103   a - d  are shown as pointed, stylus-type sharp points, however, any shape that would damage the disc could be used. Some shapes could remove more material from the disc than sharp points, but wider shapes could increase the resistance to rotating the frame. For example, a blade that is approximately 2 mm wide could scrape the entire width of the volume descriptor, but without the resistance from a blade that spanned the entire optically-readable portion of the disc. 
         [0024]    Note that scraper  10  has no moving parts. That is, while scraper  10  moves as a unit with respect to a disc, frame  100 , spindle  101  and scraping elements  102   a - 103   d  do not move relative to each other. It is possible that any of scraping elements  102   a - 103   d,  which are shown as rigidly attached to frame  100 , could be made with flexible material. However, as defined herein, a rigidly-attached, flexing element is not a moving part. Further, spindle  101  of could be adapted such that at least a portion of spindle  101  rotates along with a disc with respect to frame  100 . This could be accomplished by either having a rotating joint at the point where spindle  101  is coupled to frame  101 , or by having a sleeve that fits over spindle  101  such that the sleeve stays fixed in position relative to a disc, but rotates relative to frame  101 . 
         [0025]      FIG. 2  shows the damage done to disc  20  by scraper  10  of  FIG. 1 . Disc  20  comprises center hole  201  and optically-readable portion  200 . Center hole  201  fits over spindle  101 , as described above. Optically-readable portion  200  is shown as having sustained damage from scraper  10 . A circle comprising arcs  202   a  and  202   b  has been scraped by scraping elements  102   a  and  102   b,  indicating that disc  20  and scraper  10  have rotated at least half of a circle relative to each other. Had disc  20  and scraper  10  not rotated half of a circle, arcs  202   a  and  202   b  would not touch ends to form a complete circle. Arcs  203   a - d  are due to the scraping paths of scraping elements  103   a - d.  Disc  20  may retain intact data, but the damage is extensive enough to prevent many disc readers from reading it. 
         [0026]      FIG. 3  shows disc scraper  30 , another embodiment of the invention with no moving parts. Scraper  30  comprises frame  30  with slot  301  and scraping elements  302 ,  303   a,    303   b  and  304   a - d.  Slot  301  is sized to allow a disc to pass through with minimal or no lateral clearance. The lack of lateral clearance will ensure that scraping elements  302 ,  303   a,    303   b  and  304   a - d  cross predefined portions of a disc when the widest portion of the disc enters the slot. Prior to that, and after the widest portion of the disc has passed through frame  30 , the disc may have lateral movement. Further, a disc may have some rotational motion as it passes through scraper  30 , so scraping paths traced by scraping elements  302 ,  303   a,    303   b  and  304   a - d  may not be straight. Rather, scraping paths may be waved lines, arcs, and even looped lines. However, whatever scraping paths may be, they will cross predefined locations when the widest part of the disc is constrained to pass through the slot without any lateral movement. 
         [0027]    As shown in  FIG. 3 , scraping element  302  is approximately in the center of the widest dimension of slot  301 . Scraping element  302  will then trace a scraping path across the center point of the disc. As scraping element  302  crosses from the optically-readable portion of a disc toward the center hole of the disc, it will damage the volume descriptor. Scraping elements  303   a  and  303   b  may be positioned to trace scraping paths that are tangential to the innermost portion of the optically-readable portion of the disc, thereby scraping a larger portion of the volume descriptor than scraping element  302 . Typical discs would require scraping elements to be placed between 21 and 23 mm from the center of the widest dimension of slot  301 . 
         [0028]    In order for scraping elements  302 ,  303   a  and  303   b  to damage the volume descriptor, a disc must be inserted nearly half way into slot  301 . In typical operation, though, a disc may be passed entirely through scraper  30 , ensuring damage to the volume descriptor. At the half way depth of insertion, the sides of frame  300  constrain the position of a disc to be centered in slot  301 . That is, the sides of frame  300  act as guides for the disc, to constrain its lateral motion as it moves relative to frame  300 . If slot  301  is sized for typical CDs and DVDs, it will be approximately  12  centimeters (cm) wide, placing scraping elements  303   a  and  303   b  between 97 and 143 mm from an edge of slot  301 . 
         [0029]    Other scraping elements, such as  304   a - d  may be provided to damage a data area other than the volume descriptor. Further, scraping elements may also be placed on the opposing side of slot  301  from scraping elements  302 ,  303  and  304 . The opposing side of frame  300  may provide pressure to force a disc surface up against scraping elements  302 ,  303  and  304 . Since a typical disc is approximately 1 mm thick, slot  301  may be between 1.5 and 5 mm on its narrow dimension, to allow for the height of scraping elements  302 ,  303  and  304 , and any scraping elements on the opposing side of slot  301 . Scraping elements on both sides of slot  301  allow scraper  30  to operate effectively, no matter which side of the disc faces scraping elements  302 ,  303  and  304 . 
         [0030]      FIG. 4  shows the damage done to disc  40  by scraper  30  of  FIG. 3 . Optically-readable portion  200  of disc  40  is shown as having sustained damage from scraper  30 . Scraping path  400  is due to scraping element  302 , and crosses the volume descriptor, near the innermost section of portion  200 , twice. Scraping paths  401   a  and  401   b  are due to scraping elements  303   a  and  303   b,  and damage the volume descriptor more than path  400 , since they run tangential to the innermost section of portion  200 . Scraping paths  402   a - d  are due to scraping elements  304   a - d,  and damage portion  200  outside the volume descriptor region. Scraping paths  400 - 400   d  are shown as predominantly straight lines, however, since disc  40  may have unconstrained rotational motion relative to fame  300 , the scraping paths may not be straight. Rather, paths  400 - 400   d  may be arbitrary lines, constrained only to pass at a certain distance from the outer edge of the disc when the disc is at the half way point through slot  301 . 
         [0031]      FIG. 5  shows various options for disc scraper  50 , another embodiment of the invention that guides a disc using the disc edge, similar to the embodiment shown in  FIG. 3 . Scraper  50  comprises frame  500  and scraping elements  502 - 504   b  coupled to frame  500 . Scraper  50  is shown with guide  505   a,  protruding from frame  500 , along with optional guide  505   b  and optional pressure elements  506   a  and  506   b.  Optional pressure elements  506   a  and  506   b  are shown with optional scraping elements  507   a  and  507   b,  and are optionally spring-loaded, using springs  508   a  and  508   b,  in order to provide pressure for a disc against scraping elements  502 - 504   b.  In order to damage the volume descriptor of a typical disc, scraping elements  502 - 503   b  should be between 97 mm and 143 mm from guide  505   a.  This ensures that when guide  505   a  is against an edge of the disc, and scraping elements  502 - 503   b  cross the central area of the disc, they will also contact the volume descriptor. 
         [0032]    Guide  505   b  is optional because is it possible to align scraping elements  502 - 503   b  to damage a volume descriptor by pressing only guide  505   a  against the outer edge of a disc on one side. Further, it is possible for a user to maintain pressure on a disc against scraping elements  502 - 504   b  similar to the operation of scraper  10  of  FIG. 1 , without optional pressure elements  506   a  and  506   b.  Pressure elements  506   a  and  506   b  are shown as separated, rather than a single piece spanning from guide  505   a  to guide  505   b.  If pressure elements  506   a  and  506   b  were connected to form a single piece, scraper  50  would then comprise a closed slot, similar to scraper  30  of  FIG. 3 . Scraping element  504   a  is shown flexibly coupled to frame  500  via spring-loaded cavity  509 . While the embodiments shown in  FIGS. 1 and 3  are described as showing no moving parts, any of the scraping elements could be adapted to move in spring-loaded cavities, similar to lock tumblers. This could ensure that multiple scraping elements contact a disc even when the disc flexes. Scraping elements that move into and out of cavities in a frame will be fixed in two dimensions relative to the frame, and able to move only in one. 
         [0033]      FIG. 6  shows method  60  for using an embodiment of the invention, such as the one shown in  FIG. 1 . In box  601 , spindle  101  on scraper  10  of  FIG. 1  is inserted through a center hole of a disc. In box  602 , the user rotates scraper  10  relative to the disc while maintaining pressure to force the disc against scraper  10 . The disc is then rendered unreadable by the majority of disc readers.  FIG. 7  shows method  70  for using an embodiment of the invention, such as the one shown in  FIG. 3 . For scraper  30 , a disc is inserted into slot  301  in box  701 . The user then slides the disc through the slot in box  702  to render the disc unreadable. 
         [0034]    As used herein, the term scraping element includes narrow, pointed tips that scratch a thin line, as well as broad blades. Also, as used herein, the terms CD and disc include all optically-readable discs, including commercially-prevalent 12 cm wide discs. Some embodiments of the invention, such as the embodiment shown in  FIG. 1 , may operate reliably on differently-sized optical media, including optically-readable business cards and minidiscs. Embodiments may also be used on non-optical media, if the media includes a portion, such as an index or volume descriptor, that stores information that allows for the use of the media. 
         [0035]    The embodiments disclosed herein are self-aligning with respect to the volume descriptor. That is, when a guide engages a disc, whether the guide comprises spindle  101 , slot  301 , the edge of slot  301 , or edge-engaging protrusions  505   a - b,  each scraping element will trace a pre-determined path across a disc. This is in contrast to any device in which a scraping element may trace a path across a disc at an arbitrary position relative to the index. 
         [0036]    Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.