CA2025504A1

CA2025504A1 - Method and device for the protected transmission of data

Info

Publication number: CA2025504A1
Application number: CA002025504A
Authority: CA
Inventors: Willi Buhn; Erich Naf
Original assignee: Willi Buhn; Erich Naf; Omnisec Ag
Current assignee: Omnisec
Priority date: 1989-09-18
Filing date: 1990-09-17
Publication date: 1991-03-19
Also published as: EP0418742B1; DE59008628D1; ZA907305B; ATE119705T1; US5245655A; EP0418742A1

Abstract

ABSTRACT

A ciphering device (1) encodes the original data and converts it into signals for an output device (5) that creates a document (6, 10) out of them. This document is fed into a sending device (12) that scans the data (7) line by line and converts the result into signals that are transmit-ted to a receiving device (13) via a transmission link (14).
The receiving device (13) produces a copy (15) of the docu-ment (6, 10) out of the transmitted signals, which is fed into a reading device (17). This device converts the data into signals for a deciphering device (18) which decodes the data and converts it into signals for an output device (20).
From them, the output device (20) restores the original data and makes it available for further processing.
The transmitting device (12), the receiving device (13) and the transmission link (14) form a telecopying system. The encoding of data (7) is done by using a code that is insensi-tive to transmission errors of the telecopying system and, in particular, to distortions in the line feed direction. The code is preferentially binary with logical values contrasting in brightness and/or color, for instance it is a bar code with bars (9) parallel to the line feed, and it can be read be a reading device (17).
The parts of the system in a transmitting-end device or a receiving-end device are preferentially integrated.

(Single Figure)

Description

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A Method and a device for the protected transmission of data The invention relates to a method fox the protected transmission of data with a telecopyiny system incorpo-rating a sending device, a receiving device and a trans-mission link in-between, as well as one device each at the transmitting and the receiving ends ~or the execution o of the method.
It must be understood that in connection with the definition of the invention and the execution of the method according to the invention, no differences between the terms "device", "appliancel', "apparatus" and other words of similar meaning are to be insinuated. The dif-ferent parts of the system required for the execution of the method, which in relation to the transmitting link are located at the transmitting end or at the receiving end, can be separate, or partly or fully integrated.
Besides, it must be understood that in connection with the definition of the invention and the execution of the method according to the invention:
The qualification of a feature as "visible" signi fies that the presence of this fea~ure can ba detected 2S with the naked eye. However, it does not mean that thevisible item can be clearly identified as sign, symbol, code or the like, and even less that the visible item clearly carries a piece of information that can be uti~
lized by humans. For example, spots distributed at random on a document are "visible", but one cannot recognize in them any kind of writing and no sense whatsoever. ;;
The qualification of a feature as "legible" signi~
fies that the presence of this feature can be ascertained with the naked eye and that the visible item can be clearly identified as sign, symbol, code or the like.
However, it does not mean that the visible item clearly .. .. . ... .... . .. .

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carries a piece of inPormation that can be utilized by humans. For example, characters of an unknown language put together in a certain order on a document are "legi-ble", yet no sense is recognized in them, i.e. no infor-mation.
The qualification of a feature as "intelligible"
signifies that (i) the presence of this feature can be ascertained with the naked eye and that (ii) the visible item can be clearly identified as sign, symbol, code or the like, and that ~iii) it clearly carries a piece of information that can be utilized by humans. For instance, texts written on a document in a known set of characters and language are "intelligible".
Graphic representations can be visible, legible or intelligible, depending on their shape.
Encoding (ciphering) renders intelligible data non-intelligible but leaves them legible. Decoding (decipher-ing) renders non-intelligible but legible data intelligi-ble.
Since encoded data is non-intelligible, its trans-mission in a telecopying system re~uires measures to be taken in order to guarantee its legibility, because il-legible parts of data cannot be decoded anymore, which means that a part of the message to be transmitted has been finally lost.
The most obvious measure for the transmission of encoded data, while guaranteeing the decoding possibili~
ty, is error-free data transmission.
Error-Pree data transmission through a transmission link which is not distortion-free can in general be ac-complished by means of transmission protocols and~or by the transfer of additional information: these measures permit a regeneration of the distorted information. The required additional information may be, for example, that the information is encoded in characters which can be recognized by a reading device in spite of a certain dis-:. . ~ . . ; . - - - .

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tortion (for example, the OCR-fonts were devised for this purpose). Yet, the transmission link must still meet cer-tain minimum requirements as regards transmission safety:
only if these minimum requirements have been met is it possible to transmit encoded and thus non-intelligible data.
These minimum requirements, however, will not have been met, if the transmission link is susceptible to er-rors and/or involves an optical interface having a high lo distortion factor. In this case, the transmission errors become so frequent and~or of such a kind that no error correction is possible, thus rendering the transmission of encoded and thus non-intelligible data impossible.
The nowadays customary telecopying system that scans a document line by line, and creates a copy of it, line by line, is an axample of a transmission link with an optical interface, which possesses a high distortion fac-tor. It is a known fact that the reproduction of the original on the telecopy of a telecopying system often contains already errors in the direction of the lines ~full lines may be missing), even though in a yet tolera-ble measure. Nevertheless, at a right angle to the direc-tion of the lines (i.e~ in the direction of paper trans-port), there are often large distortions which may be so large that parts of the text may be missing or so illegi~
ble that somebody cannot even guess the meaning of a plain text by means of the copy and needs to rRquest the repetition of the transmission.
Telecopying systems are already being developed that are not required to scan a document explicitly line ~y line and produce a copy of it line by line. For example, the document may be scanned by means of a matrix of CCD-sensors, thus resulting in extreme cases in an completely parallel and not in a serial scanning. Nevertheless, the signals supplied by the matrix must be transferred en-tirely serially (bit by bit~ on a one-channel transmis-r~

sion link. While on a multi-channel transmission link the transmission is done in a parallel way (all bits of e.g.
a byte or word in parallel), the transmission of the bytes or words is still serial. Thus, such telecopying systems are still operating in a serial mode, even though this is only implicit.
The same problems connected with serial transmission remain to ba solved, regardless of whether the telecopy-ing system operates explicitly or implicitly in a serial mode.
If the information transmitted is encoded data that is non-intelligible, there exists no possibility of cor-recting errors by means of the human intellect or of re-generating missing data. This can be deduced from the 15 fact that encoded data possesses the character of random ;
data. In such circumstances the transmission of encoded and thus non-intelligible data is impossible.
Yet, there is a demand for the transmission of en-coded and thus non-intelligible data by way of a custom-ary telecopying system. For example, business people ontrips want to be able to take advantage of the telecopy-ing facilities that are nowadays provided in modern ho-tels and press centers of exhibitions, fairs, etc. and that are accessible to the public, in order to transmit messages rapidly and with ease. On the other hand, and especially in these circumstances, there exists the great danger that also one's rivals learn about this exchange of information by telecopying machine in an unduly way, for example, by accidentally or on purpose reading the messages, for instance on the telecopiex in the press center, or even by tapping of the transmission link.
Hence, it had been long-cherished, however, not pos-sible so far to transmit a confidential piece of informa-tion by means of an entirely customary, publicly accessi-ble telecopying system in a legible but non~intelligibleway. The frequently deficient and heavily scattering .. . .. .. .

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quality of the data transmission of a telecopying system has so far not allowed to convert a plain text or a graphics into encoded data, to write it, for example, in OCR-font or in any given symbols on paper, to have the 5 resulting document transmitted via a customary, publicly accessible telecopying system, to receive the transmitted copy of the document by means of a reading or recognition device (for example with a scanner with a recognition program for OCR-font or symbols), to decode the signals from the reading or recognition device in a deciphering device, and to print the decoded data or display it on the monitor: the transmission via a customary telecopying system is not good enough so as to guarantee at the re-ceiving end that all OCR-characters or symbols will be recognized without errors, while an insecurity cannot be remedied by means of reasoning, as is the case with plain text, be~ause the data are encoded. In the most unfortu-nate of cases, a read error may occur at the beginning of the transmitted message and render impossible the decod-20 ing of the entire piece of information. -Most recent developments in the field of telecopying systems give rise to expectations that before long tele-copying systems will be available which are able to proc-ess also OCR-font with adequate transmission quality and optical resolution, thus guaranteeing at the receiving end that all OCR-characters will be recognized without error. Yet, the great existing amount of customary tele-copying systems installed is not going to be replaced immediately and everywhere by telecopying systems of this new generation, not least for financial reasons. The previously mentioned disadvantages of the customary tele-copying systems will therefore continue yet for quite some time and need to be overcome.
Therefsre, it is the object of the invention to per-mit protected data transmission of non-intelligible data by using customary telecopying systems.

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It is known to input the "original" data to be transmitted into a ciphering and output device that en-codes it and outputs the resulting encoded data on a pa-per tape. The paper tape carries legible data as holes punched into the paper, however, which in their encoded form is non-intelligible for non-authorized persons. The paper tape is now fed into a sending device that scans the legible data on the paper tape line by line in combi-nation with the line feed. The result of the scan is lo transmitted by the sending device as converted electric signals through a transmission link to a receiving de-vice. The receiving device produces a copy of the punched paper tape according to the received signals, on which the data is legible but in its encoded form non-intelli-gible for non-authorized persons. This copy is fed into a reading and deciphering device which reads the data off the paper tape, deciphers it, and outputs the resulting deciphered data to an outputting device that restores the original data and makes it available for further process- `
ing as intelligible data on paper or at the monitor (for example by visualization, for machine control, etc.).
This known type of protected data transmission func-tions only in combination with a paper tape punch and a paper tape reader, which are compatible with the usual public telex system but not compatible with the usual public telecopying system. However, it is known that the public telex traffic is decreasing these days, while the public telecopying traffic is increasing strongly: hence, a solution based on punched paper tape and telex traffic does not correspond to the current circumstancas and to user needs. The telecopying of a punched paper tape is not a reasonable alternative.
From DE-A-3230201 a system for the protected trans-mission of data is known that is equipped with a tele-copying system comprising a sending device, a receivingdevice, and a transmission link in between. In this sys-- , , , ,: , ~ ~ ~

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tem the telecopying system is not a fully customary, pub~
licly accessible telecopying system. The ciphering device is integrated with the sending device and the deciphering device with the receiving device. This system does not solve the previously stated object of the invention.
From GB-A-20s7172 and GB-A-2101376 methods and de-vices for the ciphering and deciphering of intelligible data are known: The ciphered data is legible on a docu-ment as bar code. These methods and devices are in no way connected to any telecopying system and the art disclosed in GB-A-2057172 and GB-A-2101376 deals by no means with the solving of transmission problems. These methods and devices cannot contribute anything to the solution of the previously mentioned object of thP invention.
For solving khe previously defined object of the invention the method according to the invention for the protected transmission of data with a telecopying system comprising a sending device, a receiving device, and a transmission link in between, is characterized in that in combination - the original intelligible data is input into a cipher-ing device that encodes it and converts the result-ing encoded data into the corresponding first elec-tric signals, - the first signals are fed into an output device that creates a document on which the encoded data is legible in a code that is essentially insensitive in regard to transmission errors of the telecopying system, - the document is fed to a sending device which scans the legible data on the document and converts the result of the scan in~o second electrical signals, - the second signals are transmitted from the sending device via the transmitting link to the receiving device, - the receiving device creates a copy of the document out :.

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of the received second signals, on which the data is legible in the code that is essentially insensitive to transmission errors of the telecopyiny system, - the copy is fed to a reading device which reads the legible data on the copy and converts it into third electrical signals, - the third signals are fed to a deciphering device that decodes the encoded data represented by the third signals and converts the resultiny decoded data into lo fourth electrical signals, and - the fourth signals are fed to an output device which restores from them the original data and supplies it as intelligible data for further processing.
8esides, according to the invention an embodiment of the sys-tem needed for the execution of the method is preferred hav-ing one single integrated system part at the transmitting end and one single integrated system part at the receiving end.
The invention proceeds from the knowledge that the heaviest distortions caused by a telecopying system occurred in the direction of the paper feed. For this reason the meth-od in accordance with the invention preferentially utilizes a code that is essentially insensitive to the distortions oc-curring in a telecopying system in the direction of the line feed. For reaching a best possible compatibility with a tele-copying system the method in accordance with the invention pre~erentially uses a code of the mentioned kind which is a binary code whose logic values can be distinguished through a contrast in brightness and/or color between written-on and blank sections of the document. `
In addition, the invention proceeds from the knowledge that the bar code known per se is practically insensitive to distortions parallel to the lengthwise direction vf the bars.
Therefore, the code used prPfsrentially by the method accord-ing to the invention is a bar code written with bars being parallel to the direction of the line feed.
Preferentially, the legible data on the copy is read by - ~ , , - :: ,, i , :
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_ g a bar code reading device, for example a hand-held reader, a scanner, etc. This brings about the advantage that for exam-ple business people may decode a message "on the road", for example in the ho~el or eYen aboard a train or airplane, us-ing portable material, because as reading devices, handy barcode r~aders are nowadays known and inexpensive, while a lap-top computer may be used as deciphering device and its moni-tor or portable printer as output device.
Naturally, the method according to the invention may also use OCR-characters as code, if the telecopying system is capable of processing also OCR-font with adequate transmis-sion quality and optical resolution, so that it is ensured at the receiving end that all OCR-characters can be recognized without errors.
Subsequently, the invention will be described in further detail by means of an embodiment example of the method and the appended drawing.
The figure shows an example of an installation for the protected transmission of data by means of which the method according to the invention is executed.
In the represented example, a ciphering device 1 con-sists of a computer with keyboard 2 and monitor 3 programmed for operation as ciphering device. The data to be transmitted in a protected way (the "original" data) is input by means of the keyboard 2. In the ciphering device 1 this data is encod-ed according to an appropriate ciphering system. Such cipher-ing systems are known per se. The resulting encoded data is converted by the ciphering device 1 into the corresponding first electric signals and supplied to an output 4 of the ciphering device 1 for onward routing. In the example de-scribed, the output 4 is a serial output of the computer and the first electric signals correspond to a set of alphanumer-ic and graphical characters, e.g. to a subset of the ASCII-code. However, other versions are possible, for example a parallel output and/or also another code, e.g. EBCDIC, etc.
From the output 4 of the ciphering device 1 the first , ~ . . : .
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electric signals are fed to an output device 5 which in the example described is a printer, for example a cus~omary laser printer. In the example described the mentioned first elec-tric signals "a" for example on a line connecting the output 4 with the output device 5, which is indicated by the corre-sponding arrow that points at the line. From the ~irst elec-tric signals the output device 5 creates a document 6 on pa-per on which the data is written as bar code 7 with bars 9 being parallel to the direction 8 of the printer line feed.
lo While this data is legible, it is non-intelligible in its encoded form. Bar codes are known per se, in the example de-scribed the bar code 7 can be, for example, a bar code known !' as Code 128 (B) or as Code 39.
The document 6 is then removed from the printer and treated as independent document 10.
According to the invention, the document 10 is nowtransmitted by a telecopying system in order to supply a telecopy of it. Telecopying systems are well-known per se and it is for this reason that a telecopy sending device 12 and a 20 `telecopy receiving device 13 linked with one another via a transmitting link 14 are only implied in the drawing.
The document 10 is fed to the telecopy sending device 12 as is symbolized by the arrow 11. It is known that the legi-ble data on the document 10, i.e. the bar code 7, is scanned line by line in the telecopy sending device 12 in combination with the line feed. In the telecopy sending device 12 the result of this scan is converted into second electric signals that are transmitted via the transmission link 14 to the telecopy receiving device 13. In the example described the mentioned second electric signals "b" appear also on the transmission link 14 which is implied by the corresponding arrow pointing at the transmission link 14.
From the received second signals the telecopy receiving device 13 creates a telecopy 15 of the document 10 on which the data is legible in encoded form but non-intelligible.
This telecopy 15 is then removed from the telecopy re-' ' , ., :' . ~ ; ' ~: ' ~ :.

ceiving device 13, as symbolized by the arrow 16, and fedinto a reading device 17 that reads the legible data on the telecopy 15 and converts it into third electric signals "c".
In the example described the reading device 17 is a customary bar code reading pen which can be connected to a computer and is handled manually. Howevsr, different modifications of the reading device 17 are possible~ for example as automatically operated desktop model or as scanner, etc.
A deciphering device 18 consists of a computer with a keyboard 19 and a monitor 20 programmed for use as decipher-ing device. In the example described, the third signals are fed from the reading device 17 into the deciphering device 18 via a serial input 21 of the computer. However, different modifications are possible, for example a parallel input, a direct bus-connection, etc. In the example described the men-tioned third electric signals "c" appear also on a line link-ing the reading device 17 with the deciphering device 18, which is implied by the arxow pointing at this line.
In the deciphering device 18 the encoded data represent-ed by third signals is decoded according to the ciphering system used in the encoding process. Such a deciphering sys-tem is known per se. The resulting decoded data is converted into fourth electric signals and, in the example described, is fed to the monitor 20 functioning as output device in or-der to be displayed on it. In the example described the men-tioned fourth electric signals "d" appear also on a not rep-resented line linking the deciphering device 18 with the monitor 20, which is implied by the corresponding arrow pointing at the body of the deciphering device 18. Thus, the original data is restored in its intelligible ~orm on the monitor 20 and madP available for further processing. Again, different modifications are possible, for example, the output of data on a printer with or without simultaneous display on the monitor 20, an onward routing to a numerical data proc-essing unit, or merely the storing in a file on a disk, readyfor further processing.

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. ~ . , It can be seen that a transmission of data may take place via a customary telecopying system by using the method according to the invention, a pr~tected transmission of data being guaranteed at the same time. The original intelligible data cannot be perceived on the document 10 nor on the kele-copy 15. On the other hand, legible data are present and per-ceivable on the document 10 as well as on the telecopy 15, while it is advantageous for the corresponding further proc-essing that the data volume can be estimated.
Since the bar code is written in bars 9 parallel to the direction 8 of the printer line feed, the transmitted bar code on the telecopy 15 is essentially insensitive to trans-mission errors of the telecopying system parallel to the re-spective line feed direction 22 on the telecopy 15; thus, it essentially eliminates the problems caused by the distortions of a telecopying system in the line feed direction.
At a right angle to the direction 22, the sensitivity to transmission errors of the telecopying system depends on the resolution capacity of the reading device 17: the smaller this resolution capacity, the more tolerant is data transmis-sion in relation to transmission errors of the telecopying system. The cost o~ this is that transmission gets slower, because the information density is smaller. Hence, transmis-sion speed is inversely proportional to the resolution with which the data is written and read in a code being essential-ly insensitive to transmission errors of the telecopying sys-tem. It is possible for the expert to arrive at this compro-mise by means of several experiments without further inven-tive activity.
Basically, it is possible to use another binary code instead of the bar code in order to represent the data on the document 10 and on the telecopy 15. It is typical of an ap-propriate binary code that its logical values can be distin-guished by means of a contrast in brightness and/or color between written-on and blank sections of the document. This provision distinguishes such a code, for example, from paper -. ~ - : : :: . :

tape code punched into paper. Also the appropriate contrast in brightness and/or color can be ascertained by the person skilled in the art in several experiments without any addi-tional inventive activity. In this process, the contrast val-ue to be required by the output device 5 between written-on and blank sections of the document 6 is also due to the specificities of the telecopying system and the reading de-vice 17 so that the specification of a contrast value is use-ful only for a specifi d installation. Besides, such a speci-fication would correspond only to the specificities of cur-rently available installations and not take into considera-tion further developments of these installations.
The invention has been described above by means of a preferred embodiment of the method and its modifications.
However, it must be understood that the person skilled in the art can modify the described embodiment and its specificities and may introduce other modifications without leaving the invention defined in the claims.
In particular, the method according to the invention may also use, as has already been mentioned, OCR-characters or given symbols as code, if the telecopying system is able to sufficiently guarantee the necessary transmission quality and optical resolution.
For reasons of clarity, the example of a system for the execution of the ~ethod was represented, in which the system parts consist of separated devices. However, a version of the embodiment is preferred in which the various parts of the system necessary for the execution of the method located at the transmitting or at the receiving end are designed and integrated as components of a device located at the transmit-ting or at the receiving end. The preferred transmittin~-end device comprises the ciphering device l and the output device 5 as well as the previously described accessories. The pre-ferred receiving-end device comprises the reading device 17, the deciphering device 18 and the output device 20 as well as the previously described accessories.

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Claims

1. A Method for the protected transmission of data with a telecopying system comprising a sending device, a receiving device, and a transmission link in between, characterized in that in combination - the original intelligible data is input into a ciphering device (1) that encodes it and converts the resulting encoded data into the corresponding first electric sig-nals (a), - the first signals (a) are fed into an output device (5) that creates a document (6, 10) on which the encoded data (7) is legible in a code that is essentially insen-sitive in regard to transmission errors of the telecopy-ing system, - the document (6, 10) is fed to a sending device (12) which scans the legible data (7) on the document and converts the result of the scan into second electrical signals (b), - the second signals (b) are transmitted from the sending device (123 via the transmitting link (14) to the re-ceiving device (13), - the receiving device (13) creates a copy (15) of the docu-ment (6, 10) out of the received second signals (b), on which the data is legible in the code that is essential-ly insensitive to transmission errors of the telecopying system, - the copy (15) is fed to a read device (17) which reads the legible data on the copy and converts it into third electrical signals (c), - the third signals (c) are fed to a deciphering device (18) that decodes the encoded data represented by the third signals (c) and converts the resulting decoded data into fourth electrical signals (d), and - the fourth signals (d) are fed to an output device (20) which restores from them the original data and supplies them as intelligible data for further processing.

2. A method according to claim 1 characterized in that the used code is essentially insensitive to the distortions that occur in the direction of the line feed in telecopying sys-tems with a line-by-line scan in combination with the line feed (8).

3. A method according to claim 2 characterized in that the code is a binary code whose logical values can be distin-guished by means of a contrast in brightness and/or color between written-on and blank sections of the document.

4. A method according to claim 3 characterized in that the code is a bar code with bars (9) being parallel to the line feed direction (8).

5. A method according to claim 4 characterized in that the legible data on the copy (15) is read by a bar code reading device (17).

6. A transmitting-end device for performing the method of claim 1, having - a ciphering device (1) into which the original data is in-put in order to encode it and convert the resulting en-coded data into the corresponding first electric signals (a), and - an output device (5) into which the first signals (a) are fed in order to create a document (6, 10) out of them on which the data (7) is legible, characterized in that the ciphering device (1) and the output device (5) are integrated in the transmitting end device and that the latter is destined and designed to write the legible data (7) on the document (6, 10) in a code that is essential-ly insensitive to transmission errors of a telecopying sys-tem.

7. A transmitting-end device according to claim 6 character-ized in that the code being essentially insensitive to trans-mission errors of a telecopying system is a bar code.

8. A receiving-end device for performing the method of claim 1, having - a reading device (17) to which the copy is fed in order to read the legible data on the copy and convert it into third electric signals (c), - a deciphering device (18) into which the third signals are fed in order to decode the encoded data they represent and convert the resulting decoded data into fourth elec-tric signals (d), and - an output device (20) into which the fourth signals (d) are fed in order to restore from them the original data and make them available for further processing in the form of intelligible data, characterized in that the reading device (17), the ciphering device (18) and the output device (20) are integrated in the receiving-end device and that the latter is destined and de-signed to read and encode the legible data (7) on the copy (15) written in a code that is essentially insensitive to transmission errors of a telecopying system.

9. A transmitting-end device according to claim 7 character-ized in that the code being essentially insensitive to trans-mission errors of a telecopying system is a bar code.