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Claims  |
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We claim:
1. A method for scrambling an image, comprising the steps of:
receiving a scrambling key;
storing said image in a first storage device as image data in accordance
with a first data structure;
dividing said image data into a plurality of data segments, each data
segment being image data corresponding to one of a plurality of designated
areas in said image under a first mapping between said data segments and
said designated areas;
scrambling said plurality of data segments in a pseudo-random manner using
a scrambling algorithm which receives as input said scrambling key and
providing as output a scrambled image formed by associating said data
segments and said designated areas under a second mapping, different from
said first mapping, between said data segments and said designated areas;
and
storing said scrambled image in said first storage device as image data in
accordance with a second data structure.
2. A method as in claim 1, further comprising the step of providing
alignment markers to said scrambled image.
3. A method as in claim 1, further comprising the step of providing a
second scrambling key, said scrambling algorithm receives as input both
said first scrambling key and said second scrambling key.
4. A method as in claim 1, further comprising the step of transforming said
scrambled image in said second data structure to a format suitable for
data transmission.
5. A method as in claim 1, further comprising the step of providing as
output a display of said scrambled image.
6. A method as in claim 1, further comprising the step of descrambling in a
pseudo-random manner said plurality of data segments stored in accordance
with said second data structure, using a descrambling algorithm which
receives as input said scrambling key and providing as output a
descrambled image formed by associating said data segments and said
designated areas under said first mapping between said data segments and
said designated area.
7. A method as in claim 1, wherein each of said first and second mappings
between said data segments and said designated areas is one-to-one.
8. In an image scrambling or encryption application, a method for providing
one or more keys to be used in a scrambling or encryption algorithm,
comprising the steps of:
determining whether a first key used for data scrambling is to be received
and, if said first key is to be received, receiving said first key, said
first key deriving from a sequence of symbols representing keys activated
from a keyboard;
determining whether a second key for data scrambling is to be received and,
if said second key is to be received, receiving from a non-volatile
storage medium a second key; and
applying said algorithm to an image using (i) if only said first key is
received, said first key; (ii) if only said second key is received, said
second key; and (iii) if both said first and second keys are received,
using both said first and said second keys.
9. A method as in claim 8, wherein said second key comprises a key table.
10. A method as in claim 8, wherein said second key comprises data encoding
a data scrambling or encryption algorithm.
11. A method as in claim 8, wherein said step of applying said algorithm
includes the step of generating a secondary key from (i) said first key,
if only said first key is received, (ii) said second key, if only said
second key is received; and (iii) both said first and second keys, if both
said first and second keys are received.
12. A method as in claim 11, wherein said step of generating secondary
keys, if both said first and second keys are received, create a secondary
key by combining said first and second keys with a predetermined third
key.
13. A method as in claim 9, wherein said step of applying said algorithm
includes the steps of:
representing said image as a data structure in an electronic memory device,
said data structure partitioning said images into a plurality of lines
arranged in accordance with a first sequence; and
rearranging said plurality of lines in said data structure in accordance
with a second sequence, said second sequence being derived from said
secondary key.
14. A method as in claim 9, wherein said step of applying said algorithm
includes the steps of:
representing said image as a data structure in an electronic memory device,
said data structure partitioning said images into a one or more lines, and
within each line, into a plurality of segments, said segments in each line
being arranged in accordance with a first sequence; and
rearranging said segments in one of said lines in said data structure in
accordance with a second sequence, said second sequence being derived from
said secondary key.
15. A method as in claim 13, further comprising the step of descrambling,
said step of descrambling rearranges said plurality of lines in said data
structure from said second sequence to said first sequence.
16. A method as in claim 14, further comprising the step of descrambling,
said step of descrambling rearranges said segments in said line in said
data structure from said second sequence to said first sequence.
17. A method as in claim 14, wherein each of said segments in said data
structure is associated with colors in said image, said method further
comprising the steps of:
creating a segment mask, said segment mask specifying a mapping of colors;
and
applying said segment mask to each of said segments to change said colors
of said segments in accordance with said mapping of colors, prior to said
step of rearranging.
18. A method as in claim 17, where in said colors of said image are
represented by binary digits, and wherein said step of applying said
segment mask comprises applying an exclusive-or function to said binary
digits.
19. A method as in claim 1, wherein said method is used in a facsimile
machine.
20. A method as in claim 8, wherein said method is used in a facsimile
machine.
21. A method as in claim 6, further comprising, prior to said step of
descrambling, the steps of:
providing said scrambled image in hard copy form; and
scanning said scrambled image in hard copy form and providing in a second
storage device, said second storage device need not be the same as said
first storage device, said scanned scrambled image as image data in
accordance with said second data structure.
22. A method as in claim 1, wherein said method is implemented in an
application-specific integration circuit.
23. A method as in claim 8, wherein said method is implemented in an
application-specific integration circuit.
24. A method as in claim 1, wherein said method is implemented as a program
in a computer.
25. A method as in claim 8, wherein said method is implemented as a program
in a computer.
26. A sheet of paper on which is printed a marker indicating an area on
said sheet of paper, said area designating that any image outside said
area on said sheet of paper is to remain as clear text in a facsimile
transmission.
27. A marker comprising a machine-readable design to be affixed to a
designated area of a sheet of paper for specifying that any image printed
on said sheet of paper is to be transmitted in a facsimile transmission as
clear text.
28. A marker as in claim 27, wherein said marker is printed on paper coated
on one side with an adhesive material, such that said marker is to be
affixed to said sheet of paper by said adhesive material.
29. A marker as in claim 28, wherein said marker is generated by a
wordprocessor on said sheet of paper.
30. An apparatus on a sheet of paper containing an image to be transmitted,
comprising:
a first symbol for designating a first portion of a boundary on said sheet
of paper; and
a second symbol for designated the remaining of said boundary on said sheet
of paper, said boundary enclosing a portion of said image and designated
said portion of said image to be transmitted as clear text.
31. An apparatus as in claim 30, wherein said apparatus is provided on
paper coated on one side with an adhesive material, such that said
apparatus is to be affixed to said sheet of paper by said adhesive
material.
32. An apparatus as in claim 30, wherein said apparatus is generated by a
wordprocessor on said sheet of paper. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the manipulation of digital data in an electronic
document or image, so as to allow such document or image to be securely
communicated.
2. Discussion of the Related Art
In the past, data encryption methods were utilized to preserve privacy when
data is transferred through a public environment. For example, digital
encryption has been used to store data in electromagnetic storage media
and for data communication, in order to protect privacy when such media is
publicly accessible, or when such data communication occurs in a public
network or through the mail system. As another example, the Global
Positioning Satellite utilizes digital encryption techniques to encrypt
its data prior to broadcasting, so as to restrict access and to protect
data integrity. In data encryption, privacy is achieved by encoding clear
text into ciphered text. Without proper decryption, it is extremely
difficult to construct the original clear text from the ciphered text.
In general, encryption requires specific communication structures and
protocols which are different from the corresponding structures and
protocols used in a non-encrypted environment. For this reason, the cost
of providing data encryption is high. For example, ordinary communication
equipment not equipped to execute a decryption algorithm cannot receive
ciphered text to reproduce the clear text. If the transmitted data is an
image, until it is decrypted, even the encrypted image cannot be viewed,
i.e. the image can neither be printed on a hard copy nor be displayed on a
video display.
Various methods have been devised to encrypt clear text into ciphered text
to preserve data secrecy in data processing and material handling
applications. Examples of such methods can be found in the following
classes under the current classification scheme of the U.S. Patent Office:
(a) Class 283-73, Cryptogram for printed matter; (b) Class 283-17,
Cryptography, viewable but with hidden meaning; and (c) class 380-54,
Cryptography combined with overlay image. Patents relating to encryption
can be found dating back prior to 1950's.
U.S. Pat. No. 3,718,349, entitled "Cipher Device and Method" to Albert W.
Small, issued Feb. 27, 1973, discloses a cipher device and a method which
utilizes a sheet having obverse and reverse surfaces. The method disclosed
in the '349 patent requires matching several physical sheets of image to
recover the original data. Such a ciphering process is slow, and provides
only limited ciphering capability. Such method is clearly not practical
for use in a data communication network.
U.S. Pat. No. 4,529,870, entitled "Cryptographic Identification, Financial
Transaction and Credential Device" to David Chaum et. al., issued Jul. 16,
1985, discloses a means for processing a credit card or an I.D. card using
personal keys. The device disclosed in the '870 patent is a device for
coding, which cannot be used to encrypt a large document or a graphical
image.
U.S. Pat. No. 4,972,475, entitled "Authenticating Pseudo-Random Code and
Apparatus" to Carl Sant'Anselmo, issued Nov. 20, 1990, discloses a
non-linear feedback method for encrypting two-dimensional information. The
method in the '475 patent is also an encoding procedure which extends a
conventional one-dimensional bar code encryption scheme into a
two-dimensional coding scheme, thereby reducing the physical space
requirement of the encoded data. However, such a coding process cannot be
used to encrypt a large document or a graphical image.
U.S. Pat. No. 4,896,355, entitled "Patterning device for Security Facsimile
Systems" to Jerry Iggulden et. al., issued Jan. 23, 1990, discloses a
device which divides a document transmission into several separate partial
document transmissions to maintain data privacy. However, under the method
of the '355 patent, data can be compromised easily, because an
unauthorized individual can easily obtain a copy of each separate partial
document and reassemble the complete image. Such a method is not suitable
for serious applications.
An article entitled "Facsimile with Encrypted Hard Copy" by R. Myers et al,
in IBM Technical Disclosure Bulletin Vol. 20 No. 11B, pp. 4994-4995,
discloses the concept of using an encrypted hard copy output from a
facsimile machine. Myers et al do not provide technical information as to
how such a machine capable of decrypting from an encrypted hard copy can
be constructed. Myers et al discuss various problems with decryption under
such approach, but provide no definite solutions. Myers et al suggest
that: (i) use of error correction/detection would be necessary, and (ii)
the encrypted message would have to be printed at a lower resolution, with
concurrent application of a data compression algorithm.
U.S. Pat. No. 5,159,630, entitled "Facsimile Message Encryption System" to
Tseng et al, issued Oct. 27, 1992, filed May 29, 1991, discloses starting
and boundary markers to demarcate on a page of facsimile transmission an
encrypted area, while all other areas on the page are to be transmitted as
clear text. This approach restricts the amount of useful space in a
facsimile transmission, and requires the user to use a facsimile
transmission in an unfamiliar way, which is contrary to the common
practice of sending a cover page designating recipient and routing
information, to be followed by transmission of the substantive content.
Under the approach of Tseng et al, the substantive content is restricted
to the encryption area demarcated by the starting and boundary markers.
The methods of the '630 patent are hence cumbersome to apply.
Finally, a policy issue being considered by law enforcement agencies today
relates to the use of encryption by criminals to communicate with each
other in furtherance of criminal activities. Law enforcement agencies
would prefer to acquire decryption keys to all commercially available
encryption devices, so as to allow such law enforcement agencies to
decrypt any encrypted message under appropriate circumstances and
procedures (e.g. under a court order). For example, there has been
significant debate surrounding the encryption standard of the "clipper"
integrated circuit. The public and equipment manufacturers in the private
sector are vociferously resisting the requirement that governmental
agencies be given "master keys" to commercial encryption equipment. It is
therefore desirable that a method for protecting data privacy be devised
according to which government agencies can, with only moderate difficulty,
recover clear text from a protected message, while at the same time
providing adequate data privacy for most commercial applications.
SUMMARY OF THE INVENTION
The present invention provides a method for document communication, which
maintains data privacy both in digitized electronic form and in physical
printed form, and which allows data communication to utilize existing
communication equipment and software with no alteration of existing data
communication format and structures. The methods of scrambling and
descrambling under the present invention can be implemented in software or
hardware. In a hardware implementation, the present invention can be
achieved using either discrete components, or as an application-specific
integrated circuit.
In accordance with the present invention, a method is provided for
scrambling an image. Such a method includes the step of receiving at least
one scrambling key. Under this method, the image is first stored in a
storage device as image data in accordance with a first data structure.
The method then further divides the image data into multiple data
segments, where each data segment contains image data corresponding to one
of multiple designated areas covering the image. The data segments
correspond to the designated areas in the image under a first mapping. The
present invention scrambles the data segments in a pseudo-random manner
using a scrambling algorithm which receives as input the scrambling key.
The output of the scrambling step provides a scrambled image formed by
associating the data segments and the designated areas under a second
mapping, which is different from the first mapping. The scrambled image
can be printed out or displayed on a display device for viewing by the
user.
In one embodiment, a second scrambling key is used. The present invention
contemplates using only one key, only one of two keys, or multiple keys.
In one embodiment, a sophisticated key providing parameters of an encoding
scheme can be stored in a non-volatile storage medium which is portable by
the user. In such a scheme, key tables, i.e. long key sequences, or data
specifying or used with a scrambling or descrambling algorithm can be
stored in the non-volatile storage. In one embodiment, the input keys may
be combined with predetermined keys to generate multiple secondary keys.
In one embodiment, the scrambled image in the second data structure is
converted to a format suitable for data transmission. In another
embodiment, the scrambled image can be displayed on a visual display or
printed on a printer.
To descramble a scrambled image, the mapping created between data segments
and designated areas in the clear text are restored by reversing the
scrambling step. There is no information loss due to scrambling or
descrambling, when the scrambling and descrambling algorithms are chosen
to map the designated areas and the data segments one-to-one. In one
embodiment, the scrambled data is retrieved into a data file for
descrambling by scanning the scrambled image from a hard copy.
In one embodiment, the input image is divided into multiple horizontal
strips ("lines"), and scrambling is accomplished by rearranging the order
of the lines. In addition, within each line, the data segments can also be
rearranged. The order of the rearranged data segment may also vary from
line to line. Furthermore, within each segment, the image data contains
information of colors present at the corresponding area of the image.
Further scrambling can be achieved by remapping the colors in each data
segment. In one embodiment, where the colors are represented as binary
bits, remapping can be achieve by an exclusive-or operation on the binary
bits.
In accordance with another aspect of the present invention, the present
invention provides a page of image, where such a page includes a boundary
enclosing an area designating that any image enclosed within the area is
to be scrambled. Such a boundary simplifies alignment of the scrambled
image for descrambling. In this invention, a scrambled page can be printed
with one or more alignment marks generated during the scrambling process
to help position a scrambled image for descrambling. In addition, in the
context of a facsimile transmission, a document to be transmitted often
includes a cover page used to identify the content of the transmission,
routing information and the intended recipient. Normally, such a cover
page should not be scrambled. Thus, the present invention provides a
marker which includes a machine-readable distinctive design that can be
affixed to a designated area of a sheet of paper to specify that any image
printed on such a sheet of paper is to be transmitted in a facsimile
transmission as clear text. The method of the present invention recognizes
such a marker and by-passes the scrambling step for each page on which
such a marker is affixed. Such a marker can be printed on paper coated on
one side with an adhesive material, so that the marker can be affixed as a
"sticker" to such a sheet of paper at transmission time. Such a marker can
also be used to define a clear text area within which a message intended
to be transmitted as clear text can be included. In that instance, the
process to recognize such a marker would also recognize the clear text
area, so that scrambling and descrambling is bypassed for the clear text
area.
In this invention, data scrambling is performed without modifying the data
structure of the image data. The scrambling procedure does not impose any
requirement on the method of image transmission. Thus, with respect to the
data communication channel interface equipment used to transmit a
scrambled image, the scrambled image can be treated as no different from
any clear text image data. Thus, the present invention imposes no
requirement on the communication environment. The scrambled image of the
present invention conforms to all existing communication environment as to
equipment interfaces, data compression algorithms, and other standards.
For this reason, other encryption or security schemes can still be
implemented concurrently on the scrambled image of the present invention,
thereby further enhancing data security.
Further, in the embodiment where lines or segments of the image are simply
rearranged, or its colors reassigned, in a pseudo-random manner, law
enforcement agencies can reconstruct clear text of a scrambled image with
only moderate difficulty and without having to resort to knowledge of the
descrambling keys. The present invention would still provide sufficient
data privacy protection, without handing over to law enforcement agencies
descrambling keys.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a top view of facsimile machine 100, which uses the
image scrambling and descrambling method of the present invention.
FIG. 2 is a flow diagram showing the steps taken by facsimile machine 100
for transmitting an image.
FIG. 3 is a flow diagram showing the steps taken by facsimile machine 100
for descrambling an image.
FIG. 4 illustrates the operation of a data scrambling method suitable for
use in steps 240 and 241 of FIG. 2.
FIG. 5 illustrates the operation of a data descrambling method suitable for
use in steps 283 and 285 of FIG. 3.
FIG. 6 shows a method for creating from an M-key, an E-key, or both,
secondary keys for scrambling or descrambling operations.
FIG. 7 illustrates a line scrambling method using a secondary key sequence
represented by the block 410.
FIG. 8 illustrates a line segment sequence scrambling method using a
secondary key sequence K(n), which is represented by the block 880.
FIG. 9 illustrates a segment mask key method in which individual line
segments in line 810, are masked by a segment mask key, represented
generally by reference numeral 820.
FIG. 10 shows a page of document 840 on which a template 850 is imprinted
to designate an area within which the scrambled image is to be
constructed.
FIG. 11 shows a sheet of paper 900 on which is imprinted or attached a
scrambling by-pass marker 910 for indicating that the image on paper 900
is to be transmitted as clear text.
FIG. 12 shows a printed scrambled image including alignment markers 1001,
using both an M-key and an E-key, in accordance with the present
invention.
FIG. 13 shows an unscrambled image reconstructed from the scrambled image
of FIG. 12 using the authorized M-key and E-key, in accordance with the
present invention.
FIG. 14 shows by-pass markers 1200 and 1500 defining an area 1400; an image
in area 1400 is to be transmitted as clear text.
FIG. 15 shows one application of FIG. 14's bypass markers 1200 and 1500
defining a typical facsimile envelope message 1600 within area 1400.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is applicable to electronic transfer of images in
general including, but not limited to, transfer of images using a
facsimile machine. Further, although the description below illustrates the
present invention using as an example a stand-alone facsimile machine, the
present invention is equally applicable, for example, to a facsimile
machine which is part of a computer system. Typically such a facsimile
machine would include a personal computer, a "fax modem", an user
interface software package, and control software to control data transfer
between the personal computer and the fax modem. In an implementation
where paper "hard copies" of images are not involved, the images are
stored in data structures, such as data files stored in an electronic or a
magnetic storage medium.
The present invention provides data scrambling of an image ("digitized
electronic document") at the level of a data structure of the graphical
image. The scrambling method of the present invention creates a document
which is not only viewable as if it is clear text, i.e. with no change in
data structure, but also contains all the graphical information of the
digitized electronic document. The image scrambling is therefore modular
in that existing equipment can be used to transmit or receive the
scrambled image. Transmission of a scrambled image, as a facsimile, a data
file, or as electronic mail, is useful in situations where the image can
be seen or read publicly by others other than by the intended recipient.
For example, business or personal facsimile transmissions are often sent
to an individual in an office, in a hotel, or a public environment, where
the receiving apparatus is shared among many users and are attended to by
operators who should not be privy to the transmitted information. With a
scrambled image, the privacy and data integrity of the transmitted image
is not compromised, even though the scrambled image can be seen publicly.
Consequently, the scrambled image can be delivered through an unsecured
conduit, e.g. a messenger, without risking a loss of privacy or security.
Upon receipt of the scrambled document, the intended recipient can recover
the clear text image using the scrambling methods explained below.
FIG. 1 is a top view of a facsimile machine 100 using the image scrambling
and descrambling method of the present invention. As shown in FIG. 1,
facsimile 100 has a housing 520, to which a paper input tray 610 holds one
or more sheets of paper, indicated by reference numeral 510, for
individual input into facsimile machine 100. On each sheet of paper 510
may be printed a clear text image or a scrambled image of the present
invention. The output images of facsimile machine 100 are printed on one
or more sheets of paper, indicated by reference numeral 540, which are
held in paper tray 530. Each of these output images can be a scrambled
image of the present invention, or a descrambled image resulting from an
input scrambled image fed into facsimile machine 100.
To activate image scrambling or descrambling, a sequence of codes ("M-key")
constituting a "pass word" is entered through keyboard 560. Alternatively,
image scrambling or descrambling can also be activated by a second
sequence of codes ("E-key") stored in a machine-readable E-key storage
medium 600, which can be read by facsimile machine 100. E-key storage
medium 600 can be a non-volatile electronic memory, a magnetic card, a
diskette, or any other device suitable for non-volatile storage of
information. The M-key and the E-key need not be the same sequence of
codes.
To transmit a clear text image as a scrambled image, or to descramble a
scrambled image received, the user places a sheet of paper containing the
clear text or scrambled image into paper tray 610. Then, to provide the
key to be used in the scrambling or descrambling process, either the M-key
is entered on keyboard 560, or an E-key storage medium 600 is inserted
into slot 580. One or more designated keys or switches are provided on
keyboard 570 to activate scrambling or descrambling in facsimile machine
100. Of course, slot 580 represents the input slot of a reader suitable
for reading the information stored in E-key storage medium 600. In one
implementation, slot 580 is also provided with a write or record ability,
so that an E-key can be stored into E-key storage medium 600 by plugging
E-key storage medium 600 into slot 580 and pushing one or more designated
keys on keyboards 560 and 570. In that implementation, duplicate E-keys
can also be created. For security purpose, a "clear" key is provided on
keyboard 570 to clear the E-key from memory immediately after transferring
an E-key to an E-key storage medium.
As shown also in FIG. 1, an interactive display 550 provides visually
operational or error information to an operator of facsimile machine 100.
Keyboard 570 provides the command keys or switches for controlling the
operation of facsimile machine 100. Keys on keyboard 570 include an
alphanumeric keyboard (or in some instances, only a numeric keyboard) and
such keys for activating in sequence the scanning of input images from the
paper 510 in paper tray 610, or for the scrambling of the scanned images
using an M-key, an E-Key or both.
FIG. 2 is a flow diagram of the control sequence ("state machine") 120 of
facsimile machine 100 for sending a scrambled image. In FIG. 2, the "send
fax" step 200 represents an operator initiating the "send fax" command by
pushing one or more designated keys on keyboard 570. At step 210, state
machine 120 checks if an M-key is entered by the operator. An M-key is
entered by pushing the alphanumeric or numeric keys on keyboard 560.
Alternatively, a designated key on keyboard 570 is use, to indicate that
no M-key is to be entered. Regardless of whether an M-key is entered,
state machine 120 checks if an E-key would be used by checking if an E-key
storage medium is plugged into slot 580. Step 215 represents checking for
an E-key when an M-key is entered, and step 220 represents checking for an
E-key when an M-key is not entered. If neither an M-Key is entered nor a
E-key is plugged in, a clear text image is transmitted, as indicated in
FIG. 2 by the line which proceeds from step 220 to step 245, which is
labelled "SEND". Alternatively, if an M-key is not entered and an E-key is
provided, the image or images are to be scrambled using the E-key only,
the configuration parameters in facsimile machine 100 used for an "E-key
only" scrambling are set at step 235. Similarly, if both an M-key and an
E-key are provided, the image or images are to be scrambled using both the
E-key and the M-key, the configuration parameters in facsimile machine 100
used for an "E-key and M-key" scrambling are set at step 230. Otherwise,
the image or images are to be sent using the M-key only, the configuration
parameters for an "M-key only" scrambling are set at step 225.
At step 237, facsimile machine 100 retrieves a sheet of paper from paper
tray 610, and scans in the image on the paper retrieved. State machine 120
then checks if the image contains a scrambling by-pass marker. The
scrambling by-pass marker is a special marker indicating to state machine
120 that, despite a scrambling configuration is set at step 225, 230, or
235, the present scanned image is to be transmitted as clear text. The
scrambling by-pass marker is useful, for example, on a cover sheet to
provide in clear text an identification of the intended recipient and any
appropriate routing information, so that the scrambled images to follow
can be routed to the intended recipient. The scrambling bypass marker can
be any machine-recognizable symbol or code. For example, a special bar
code located within a special area can be used. Such special markers can
be provided as adhesive "stickers" to be attached on the page containing
the image to be sent as clear text. Alternatively, the special bypass
marker can also be generated by a electronic word processor, or as printed
on pre-printed stationery. An example of a scrambling bypass marker 910 on
a sheet of paper 900 is shown in FIG. 11. A variation of the special
bypass marker is an area bypass marker defining an area which is to be
excluded from scrambling. Such area bypass markers are shown in FIGS. 14
and 15 as area bypass markers 1200 and 1500 and discussed in further
detail below.
If a scrambling by-pass marker is detected, state machine 120 proceeds to
step 245 to transmit the scanned image as a clear text image. Otherwise,
step 240 is entered, during which facsimile machine 100 scrambles the
scanned image in accordance with the configuration parameters set at the
step 225, 230 or 235. Facsimile machine 100 then adds alignment markers to
the scrambled image and transmits the scrambled image at step 245.
Alignment markers are provided to help position the scrambled image for
descrambling. In the case of an area bypass marker, when such an area
bypass marker is detected, the area specified by the area bypass marker is
excluded from scrambling. At step 248, state machine 120 checks, if all
pages in paper tray 610 have been transmitted. If there are more pages in
paper tray 610, state machine 120 returns to state 237 to scan the next
input image from the sheet of paper next retrieved from paper tray 610.
FIG. 12 shows a scrambled image, including alignment markers 1001,
transmitted from a facsimile machine of the present invention which would
be received by another facsimile machine. This scrambled image can be
unscrambled using the unscrambling method of the present invention
described below with the M-key, the E-key, or both. FIG. 13 shows an
unscrambled image reconstructed from the scrambled image shown in FIG. 12.
FIG. 3 is a flow diagram showing the control sequence ("state machine") 125
for descrambling scrambled images fed into facsimile machine 100. The
steps for specifying an M-key, or an E-key, or both, for the descrambling
process are similar to the steps for specifying the corresponding keys
described in conjunction with FIG. 2. To minimize repetition, these steps
are not described again. To facilitate reference, steps in FIG. 3 which
correspond substantially to those in FIG. 2 are given the same reference
numerals. To descramble a scrambled printed document or a scrambled
digitized electronic document which is saved in an electronic storage
device, and restore the clear text corresponding to the scrambled
document, facsimile machine 100 can be activated when the corresponding
M-key and E-key are specified. At step 250, an operator places the
scrambled images in paper tray 610, and pushes one or more control keys on
keyboard 570 to initiate the descrambling steps. The M-key, the E-key, or
both, are entered and are used to configure facsimile machine 100 in steps
210, 215, 220, 225, 230 and 235 in substantially the same manner as
described above with respect to FIG. 2. When the M-key, the E-key, or both
keys are specified, the scrambled image is scanned into facsimile machine
100, aligned at step 283 according to the alignment marks and descrambled
according to the present invention at step 285. The descrambled image,
i.e. the clear text image, is then printed and output in step 260 to
output paper tray 530.
FIG. 4 illustrates the operation of a data scrambling method suitable for
use in steps 240 and 241 of FIG. 2. As shown in FIG. 4, the input data to
the method of FIG. 4 includes an M-key 15 entered by an operator, an E-key
16 read from a storage medium, such as E-key storage medium 600, and the
data of a scanned image, represented generally by data file 10. M-key 15
and E-key 16 are provided to scrambling key generating module 30, which
implements an algorithm described more fully below in conjunction with
FIG. 6, to generate a set of secondary scrambling keys.
Data file 10 is either created by a scanner in facsimile machine 100 or
received in a standard facsimile format over a communication link. Data
file 10 is mapped into a "mapped digitized electronic document" by mapping
module 18. Mapping module 18 divides the image in data file 10 into
rectangular strips ("lines"), and then divides each line into a
predetermined number of "segments". Each segment is then stored in the
mapped digitized electronic document along with an index specifying the
physical location, i.e. line number and segment number, of the segment in
the image.
Using the secondary scrambling keys generated by scrambling key generating
module 30 and conversion module 18, processing module 20 generates a
"scrambled digitized document". The operation of processing module 20 is
described in further detail below in conjunction with FIGS. 7, and 9. At
the operator's option, scrambling key generation module 30 can provide
multiple scrambling keys. With multiple scrambling keys, the scrambled
digitized document at the output of processing module 20 can be fed back
multiple times, so as to be scrambled recursively using the multiple keys
from scrambling key generating module 30. Block 25 represents a module
which adds alignment markers to the scrambled image. As mentioned above,
such alignment markers are useful to facilitate proper positioning of the
scrambled image for descrambling from a hard copy scrambled image. Blocks
40 and 60 represent data format conversion modules, which translate a
scrambled digitized document to a format compatible with the protocols of
various equipment receiving the scrambled image. For example, block 40
represents conversion to a protocol which can be used by a display device,
such as a printer or a graphical display, for generating a physically
viewable scrambled document. Block 60 represents conversion to a protocol
suitable for transmitting over a communication link, such as a telephone
line, to a receiving device, such as another facsimile machine.
FIG. 5 illustrates the operation of a data scrambling method suitable for
use in steps 283 and 285 of FIG. 3. Descrambling in facsimile machine 100
can be performed on a scanned scrambled image (represented in FIG. 5 by
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