Graphic privacy system

March 9, 1948.

J. V. L. HOGAN ET AL 2,437,255

GRAPHIC PRIVACY SYSTEM Filed June 4, 1943 3 Sheets-Sheet 1

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INVENTORS

JoTiTs WZ.JCooan· JYz&amp;yh' dTtessZer’

BY ~

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ATTORNEY

March 9, 1948. j. v. l. hogan et al 2,437,255

GRAPHIC PRIVACY SYSTEM

Filed June 4, 1943 3 Sheets-Sheet 2

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INVENTORS

JoTrn' V.Y-.Ho^ari'

<img file="US2437255A_D0006.tif" />

March 9, 1948.

J. V. L. HOGAN ET AL

GRAPHIC PRIVACY SYSTEM

Filed June 4, 1943

2,437,255

Sheets-Sheet 3

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INVENTOR

BY

AUTO.

Patented Mar. 9,1948

2,437,255

UNITED STATES PATENT OFFICE 2,437,255 GRAPHIC PRIVACY SYSTEM John V. L. Hogan, Forest Hills, and Hugh C. Ressler, Bayside, N. Y„ assignors to Faximile, Inc., New York, N. Y„ a corporation of Delaware

Application June 4, 1943, Serial No. 489,654 (Cl. 35—4)

Claims.

manner described above may be carried out by means of cutting the message in strips, assembly in predetermined order, cutting at right angles and reassembly in another predetermined order and the deciphering may be accomplished by means of a mask which exposes the squares in a predetermined order, the subject of the present application is a machine for carrying out the enciphering and deciphering automatically.

The enciphering and deciphering machine of the present invention consists of a drum to which copy to be enciphered or deciphered is attached, a drum carrying' photographic paper or film on which the enciphered or deciphered copy is reproduced and means for projecting the copy from the first drum on to the sensitized material on the second drum strip by strip in a predetermined order., In particular, both drums are rotated at different speeds and a “Strobotron” lamp is flashed at predetermined instants whereby strips, of subject matter from the first drum are photographically transferred to the second Hmm These strips of subject matter are thus mixed in a predetermined manner.

In order to carry out the second mixing step the photographic copy produced by the first step is developed, turned at right angles, mounted on the first drum and copied again strip by strip in a second predetermined arrangement on the second drum. The second copy, when developed, is a positive copy of the original randomized in two dimensions.

An additional factor may be added by exposing only _a portion of each drum, say one third, at each run, repeating a second and third time to completely cover the field in three runs. A simple mask may be used to accomplish this additional randomizing. The mask is shifted and the key changed, or a new starting point chosen as each 40 Portion of the copy is randomized.

The completely enciphered copy may be transferred by any suitable means to a receiving point as, for instance, by wire or radio facsimile. At the receiving point the message may be deciphered by repeating the enciphering process in reverse. The same machine above described is suitable for this deciphering.

In the drawing:

Fig. 1 shows a simple geometrical figure to be transmitted privately and a second figure included to add confusion.

Fig. 2 shows the figures of Fig. 1 partially enciphered.

Fig. 3 shows the figures of Fig. 1 fully enciph-

The present invention concerns enciphering and deciphering of graphic material for privacy by automatic machinery.

One object is to provide means for mechanically and automatically enciphering and deciphering graphic material for privacy purposes.

Another object is to provide an enciphering and deciphering machine in which a very large number of ciphering key combinations are possible.

Still another object is to provide a machine in which the key combinations may be readily changed.

A further object is to provide a machine capable of varying degrees of privacy from a moderate order to a very high order.

A still further object is to provide a machine for enciphering graphic material in a form particularly well adapted to facsimile transmission.

These and other objects will be evident from the detailed description of the invention, given in connection with the various figures of the drawing.

The ciphering operations to be accomplished by the devices of the present invention consist of four fundamental operations. The first operation is, in effect, dividing the clear subject copy into a number of horizontal strips of predetermined width. The second operation is the transposition of these strips in an order predetermined by the horizontal key selected, which key must be known by both the sender and the receiver of the ciphered subject copy. The third operation consists of dividing the partially enciphered copy (produced by operations 1 and 2) into strips of predetermined width but at right angles to the first dividing operation. The fourth step is the transposition of the resulting strips according to a mutually known key for the vertical randomizing of the copy, which may differ from the key first used. The result of the four operations is a ciphered message which can be delivered to its destination by mail, by courier, by facsimile or otherwise.

Where additional security is required, the subject copy ciphered as above described may be 45 reciphered or remutilated by subjecting it to the same four operations two or more times. Where a second ciphering is used, it is preferred that the effective dividing of the copy be done along lines which fall midway between the dividing lines 50 used for the first ciphering. Where three successive cipherlngs are used, the second and third divisions may each be displaced by one-third of the strip-width, etc.

While the enciphering of the message in the 55 ered*

9.437.906

Fig. 4 shows an automatic enciphering and deciphering machine according to the present invention.

Fig. 5 shows a modified form of optical system which may be used in the machine of Fig. 4.

Fig. 1 shows a square copy to be enciphered, including a large triangle representing the figure which it is desired to transmit to a receiving point and a small triangle added to confuse a possible Interceptor.

Fig. 2 shows the result of dividing Fig. 1 into eight equal vertical strips and rearranging these strips in a predetermined order, according to a key. Fig. 2 represents a partially enciphered copy.

Fig. 3 shows the result of dividing the partially enciphered copy of Fig. 2 into eight equal horizontal strips and arranging these strips in a second predetermined order according to a second key. Fig. 3 represents the fully enciphered copy.

The original copy may be restored by reversing the process, first restoring the original order of horizontal strips and second restoring the order of the vertical strips. It will be noted in the enciphered copy of Fig. 3 that the portions of the small triangle appear as confusing elements of the same character as the portions of the large desired triangle.

Fig. 4 shows a machine, according to the present invention, for enciphering or deciphering graphic copy. The subject drum I carries on its surface graphic copy 22. A longitudinal strip of copy 22 of predetermined width is projected upon second drum 18 by means of suitable optical system 17. Drum i is rotated at a substantially constant speed by means of motor 16, while drum 18 is advanced a step at a time by a stepping device 19. For each position of drum 18 a predetermined section of copy 22 is projected onto drum 18 by means of the high speed flash lamp 5. A sheet of photographic paper or film is attached to the surface of dram 18 which when developed will reproduce copy 22 in randomized strips. Two strips are shown on drum 18 at 20 and 21.

When dram 18 has completed one revolution and the paper or film developed, a negative randomized strip image of copy 22 is produced. This represents the first step in enciphering the copy. To accomplish the second step, the partially enciphered negative is attached to the surface of dram I turned at right angles to the original position, so that the strips run around the drum. The step by step randomized copying process is carried out with a second photographic paper or film on drum 18 and using a second randomizing key. The result when this second paper or film is developed is a copy randomized in two dimensions that is in small squares. This second enciphered copy will be a positive copy which may be transmitted to a receiving point by any well known means as, for instance, by facsimile. Still further privacy may be provided by exposing only a portion of the length of the copy at each revolution of drum 18 and repeating the rotations until the entire drum is covered. A further degree of privacy may be added or substituted for this past process by displacing the second copy by a fraction of a strip width on drum 1 and repeating the two enciphering steps any desired number of times.

Lamp 6 may be flashed once at some predetermined point during each revolution of drum I and dram 18 stepped once at each revolution, or lamp S may be flashed two or more times at each revo4 lution of drum I, stepping dram 18 once at each flash to produce an “Interlaced” randomizing.

The remainder of Fig 4 shows one means, according to the present invention, for flashing lamp 5 5 and advancing drum 18 in accordance with a predetermined sequence.

Lamp 5 may be any suitable high speed lamp which may be ignited for an extremely short interval of time. Lamps which provide illumina10 tion by means of ionized gas are capable of producing intense light for a period of time of the order of Woo.ooo second and may be “triggered” by means of an electrical impulse. The timer unit 23 may be any well known device for flashing .. lamp 5 in accordance with electrical impulses fed ° to it over wires 24, 27 and 29. Electrical impulses spaced corresponding to the desired strip width are generated by tone wheel 3 attached to shaft 2 of drum I. The number of teeth on tone wheel „₀ 3 correspond to the number of strips to be pro^ύ duced from copy 22. Magnet 4 generates the tone wheel impulses which are fed to timer 23 oyer wire 24. Impulses from tone wheel 3, however, are not passed to lamp 6 unless the circuits _ thru leads 27 and 29 are completed. The sequence ²⁵ of flashing of lamp 5 is controlled by the circuits connected to these leads 27 and 29.

On the same shaft with motor 16, driving drum I, are mounted a commutator 14 and collector rings 6, 7, 8, 9, etc. There are as many commutator segments in 14 as the number of strips into which the copy is to be photographically divided. Assuming that the circumference of drum I would take subject copy 8 x 8” in size and that ₃₅ adequate privacy would be provided by using % ⁰ strips, there would be 16 commutator segments and 16 collector rings, and 16 impulses per revolution would be generated by tone wheel 3. The commutator 14 has a single stationary contact 15, and individual stationary contacts 13, 12, II, 10, ^u etc., are provided for the 16 collector rings. One commutator segment is electrically connected to each collector ring.

It will be noted that each segment on com_4g mutator 14 corresponds in position to one of the ⁰ 16 strips into which the subject copy is to be divided. If for each revolution of drum I, a different selected strip of the subject copy is photographed, the first two operations can be com50 pleted in 16 revolutions of dram I. The circuit of lamp 5 is connected (but not phased) to expose any particular strip (for photographing) by connecting through contact 15 and the appropriate collector ring contacts 13, 12, II, 10, etc. If 55 connection is made to 12, for example, the lamp circuit will be closed when the second strip is opposite the aperture lens 17; if connection is made through 10, the Strobotron circuit will be closed when the fourth strip of the clear subject _eo copy is opposite the lens 17, etc.

Functionally, the rotating switch 41 controls the lamp circuit and the stepping operation of the copying drum 18. This switch has a rotary arm 80 turned continuously by a back-geared motor 65 not shown and sweeping continuously over the series of contacts shown. The third, sixth, ninth, twelfth, etc., contacts are marked 65, 69, 72, 75, etc. Immediately after each such contacts are contacts marked 66, 70, 73, 76, etc., and all of 70 these contacts are connected together by means of connection 67. After each of these contacts and before the next of the first set of contacts are blank interval contacts marked 68, TI, 74, 77, etc., which are not electrically connected. 75 After the final contact of the first set of con2,487,265 tacts is a single contact marked 64. The rotary arm 80 is moved continuously in a clock-wise direction at such speed that drum I makes one complete revolution while arm 80 is passing across a single contact, and for this purpose it would be advantageous to gear the shaft of the switch 41 to the motor 16.

The operation of the rotary switch is such that as the arm 80 sweeps over the contacts, it first closes a lamp selecting circuit from 65 (through a transportation block or set of blocks to be described) to some one of the collector ring contacts 13, 12, etc.; this latter contact corresponding to the particular strip of the subject copy on drum I which is to be photographed in the first or top position on the sensitive paper carried by drum 18. After leaving 65, the arm 80 passes to contact 66 which actuates the step-motor 19 of drum 18, so as to rotate drum 18 through an angle corresponding to one strip; this operation exposes the second strip of the sensitive paper on drum 18 through the lens 17. Rotary arm 80 next passes across idle contact 68 so allowing snfficipnt. time for all mechanical transients to die down before the next photographing operation. In some , cases the idle periods represented by contacts 68, 71. etc., may be minimized or eliminated, or merged into contacts 66, 70, etc. Arm 80 next reaches contact 69 which is connected to another one of the 13, 12, etc. collector contacts by way of the transposition block or set of blocks, so setting up the lamp circuit to photograph a different key-selected strip from the clear copy on drum ί in the second position on drum 18. This cycle is repeated until the rotary arm 80 has passed over all 16 of the 65, 69, etc. contacts and the drum (8 has rotated through all 16 of its positions, with the result that the whole of the subject copy has been photographed upon the sensitive paper mounted on drum (8. The arm 80 then passes to stop-contact 64 which may automatically disconnect power from all parts of the machine and.signal that the operation has been completed by turning on a lamp or buzzer.

A simple form of transposition blocks for providing changes in the key is shown. They comprise cylinders 30, 42,46 and 50, carrying numbers of contacts 31, 43, 47, 51, etc., placed axially in rows of sixteen, and arranged to be rotated either by hand or automaticaly in steps by stepping motors 40, 45, 49 and 53, which may be simple magnetic pawls and ratchets. On one side of the cylinders 30, etc., there are sixteen stationary contacts 31, 43, 47, 51', etc., respectively connected to the collector ring contacts 13, 12, II, 10, and on the other side are sixteen similar stationary contacts which are connected to contacts 65, 69, 72, 75, etc., of the rotary switch 41. Within the transposition block there are cross connections for each position between opposite sets of contacts, so that with transposition block 30 in its first position, it will be connected to a predetermined advanced contact on switch 41. The step control 40, etc., of the transposition blocks may be connected to contact 64, so that the transposition block will be moved forward one step for each revolution of the rotary switch 41. This will result in selecting, in accordance with the connections within the various transposition blocks, the order in which the strips of the subject copy on drum I will be photographed on drum 18. For example, if in the first position of drum I (exposing the top strip) and the first position of the transposition block, collector ring contact 10 is connected to rotary switch contact 65, the fourth strip on drum I will be photographed into the first position on drum 18. In the second position of the transposition block, the twelfth strip on drum 1' might be selected for photographing in the first position on drum 18, etc. Thus, the key of the cipher is changed by rotating the transposition blocks 30, 42, 46, 50 from one step to another, or by substituting another differently-connected transposition block. Evidently the invention is not limited to the number of transposition blocks used as all four may be combined in one, two or any desired number of composite blocks or they may be further divided.

In order to avoid irregularities in the timing of the lamp 5 such as might result from contact difficulties if the commutator contact 15 alone were relied upon, it is proposed to use the commutator 14 Only to establish the desired circuit corresponding to the strip to be photographed, and to rely upon a sharp impulse from a tone wheel 3 to ignite the lamp at exactly the instant when the desired strip to be photographed on drum I is centered under lens 17.

The deciphering operation is mechanically and electrically the inverse of that which has been described for ciphering. The same transposition blocks are used, but connected reversely, so as to replace the randomized strips,, upon rephotographing, into their original positions. The ciphered subject copy is placed on drum I and the resulting clear copy will come from drum 18 (after either two or four operations, according to the mutilation process used in ciphering).

The system of the present invention can be 35 so applied as to give a long term of privacy for graphic material, whether pictorial or textual. The only means of breaking the system would appear to be the tedious piecing together of the small square elements. Since these elements are 40 identical in size and shape, their contours offer no clues for their reassembling. If they are made sufficiently small in relation to the character of subject copy, the time required for their assembly should be quite substantial.

The limitation of the system in term of privacy appears to be determined principally by the mechanical and optical precision that can be built into the ciphering and deciphering machine; it is proposed that by using the tone wheel and positioning stops of relatively large radius, a satisfactorily high degree of mechanical precision can be had without too great difficulty.

The speed of operation of the system is not too strictly limited. If half-inch strips, for example, ; gave adequate privacy, it is possible to make the sixteen photographic exposures for each operation in less than sixteen seconds, and allowing two minutes each for developing, washing and blotting the photographs and replacing them on drum I, the enciphered message is produced in less than five minutes for a single cross mutilation and in less than ten minutes for a double cross mutilation. This relatively short time required for enciphering or deciphering is made possible only by the crossed strip technique upon which this system is based.

It should be noted that for any particular width of strips and number of photographing operations, the term of privacy can be extended by giving attention to the character of the original clear subject copy. For example, contour lines may be shown as a series of dots or dashes, that continental outlines or other identifying characters may be omitted and the bench mark and overlay principle applied, and also that the clear

2,437,266 copy may contain irrelevant material constituting nulls which would further confuse an intercepting operator who might endeavor to reassemble the elements of the message. Still further protection can be had by making the significant clear copy only a portion of that which is transmitted as the message (e. g., by using a drum of a larger radius or greater length than is necessary for the copy to be transmitted, and filling the excess area with similar graphic material having no significance. These and similar expedients would increase the difficulty of breaking the ciphered message by attempting to solve it as a “picture puzzle,” and thus increase the term of privacy. (To date, no other way of breaking the cipher has been discovered.)

A further element of complexity, based on the same principle of automatically randomizing the positions of equal-sized and identically shaped elements, may comprehend a series of operations in which the subject copy is processed three times at angles of 60°. This would result in the randomizing of a large number of equilateral triangles, rather than squares, but, while the process would generaly follow the square-element method outlined in the foregoing, the machine involved would be considerably more complicated. It is believed that adequate privacy can be obtained by the square method without introducing the complications inherent in dividing the clear copy into triangular or hexagonal units.

Fig. 5 shows a modified optical system which may be substituted for the optical system 11 of Fig. 4 in order tc transfer graphic material from drum I to drum 18 a small square at a time instead of in strips. This optical system of Fig. 5 includes suitable lenses 81 and 82 mounted in lens tube 89 for projecting a predetermined small square area 98 from drum I to a corresponding square area 99 on drum 18. Drums I and 18 are rotated as in Fig. 4 and optical system 81—82—89 is moved along the axial direction of drums I and 18 by suitable means as, for instance, motor 95 and gear 94 driving gears 92 and 93 attached to lead screws 90 and 91. Lens assembly 81—82—89 is mounted on lead screws 90 and 91 and is hence moved back and forth in accordance with the energizing of motor 95. Motor 95 is energized over leads 96—97 from a contact or contacts as contact 63 on rotary switch 41. Thus the motions of lens system 81—82—89 and drums f and !8 permit randomizing the copying of material from drum I on drum 18 a square at a time in a predetermined sequence. A circumferential strip on the drums may be copied with the squares randomized within the strip, the lens system shifted the width of a strip, and the process repeated until the entire copy is transferred.

A further element of randomizing may be added by the use of means for rotating the squares being transferred by varying integral multiples of 90 degrees. This may be accomplished, for instance, by means of the totally reflecting 90°-45°-45° prism 83 which is included in the optical path between drums I and 18. This is a well known optical device which rotates the image by an amount equal to twice the physical rotation of the prism. Thus the orientation of the material within a square may be randomized. Prism 83 may be rotated by any suitable means as, for instance, motor 88, gear 85 attached to the shaft of motor 86 and ring gear 84 attached to lens tube 89 carrying prism 83. The exact positioning of prism 83 at angular positions which are integral multiples of 45 degrees may be in8 sured by detent 100 operating on a notch in the side of ring gear 04 and at a relatively long radius for high accuracy. Motor 06 may be energized also from a point on rotary switch 41 thru leads 87—88. Hence, with the machine of Fig. 4 as modified in Fig. 5, is capable of dividing copy into a large number of squares in which the image within the individual squares is rotated by 0, 90, 180 or 270 degrees and in which the location of the squares is randomized within any circumferential strip. Complete randomization of the positions of the squares may be accomplished by moving either drum I or drum 18 along its axis by predetermined amounts during the copying process.

Any degree of privacy may be attained by repeating the randomizing process with the copy randomized in a previous operation displaced along drum 1 by a predetermined fraction of a square width. For instance, the randomizing may be carried out three times with the partially enciphered copy displaced one-third and two-thirds of a square width for the second and third passes respectively.

Further privacy may be attained using any given degree of randomizing by special treatment of the copy to be enciphered. One very effective method of preparation is to use dotted lines on the original copy, so that no continuous lines appear at the edges of the squares to assist in matching. Preparation of the copy so that only one dot appears in each square and especially if this one dot is made to appear at the center of ths square provides enciphered copy which is impossible of “breaking” within moderate period of privacy.

The machines described above have been explained as applied to the enciphering process. The enciphered copy is transmitted to a receiving point by facsimile, messenger or other suitable means. The received copy may be deciphered on the same machine used for enciphering, by inverting the order of randomizing.

While one embodiment of the present invention with a few modifications has been shown and described, many modifications are possible within the spirit and scope of the invention, as set forth in the appended claims.