US2518458A - Authenticating device - Google Patents

Description

Patented Aug. l5, 1950 more!) STATES OFFICE AUTHENTICATIN G DEVICE William F. Friedman, Washington, D. 0.

Application August 25, 1944, Serial N 0. 551,172

1 Claim. (Cl. 35-4) (Granted under the act of March 3, 1883, as amended April 30, 1928; 3'20 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment of any royalty thereon.

This invention is an authenticating device and, particularly, is a device by means of which the bone. fides of certain types of messages can be readily proved.

It is customary in certain fields of commerce, as for instance banking, to transmit cable and radio communications in code or cipher, rather than in clear text. This is economical, and serves in some measure to protect the interests of customers and of the commercial institutions themselves. According to the following description, this invention is to be used by banking and other financial institutions, but it will be obvious that it is applicable as well to other types of businesses, and has military applications as Well.

In the drawings:

Figure 1 is a digaram of one of the mixing or scrambling elements used in the invention.

Figure 2 is a diagrammatic representation of the authenticating device of this invention.

The invention comprises a group of ten mixing elements in the nature of cryptographic rotors. One such rotor is shown in Figure 1, where it may be seen to consist of a body member Hi, formed of Bakelite or some other insulating material, and a group of ten contacts 11-20, inclusive. A second group of contacts, 2 l-Sil, appears on the opposite face of the body member.

The contacts I l-Zfl will normally serve as input contacts and the other set will normally serve as output contacts. Connections between the several input contacts and the output contacts are made at random or according to some predetermined complicated rule. The result is, of course, that an input signal representing one condition is converted to an output signal representing something entirely difierent.

Referring to Figure 2, the invention may be seen to include a shaft 35, supported at its two ends in members 38 and 39. The members 38, 39 may be of any form desired. Their only functions are to support the shaft 35, and to carry stationary electrical contacts, 41-50, on the one hand, and 5l-6il, on the other.

Mounted on the shaft 35 are ten cryptographic rotors "i l-Bll, such as that illustrated in Figure l, and earlier described. The rotors are all essentially similar, but their internal wiring normally Will be diiferent. The rotors bear on their peripheries indicia of one type or another, the type depending, to some extent at least, on the material or non-make position 98.

2 to be handled by the authenticator. In Figure 2, rotors H and T12 and i i-36 bear ordinary Arabic numerals arranged in normal order from 0 to 9. Rotor it carries symbols representing the money of various countries. The rotors are, in additon, identified by number, as St, or otherwise, so that they can be readily arranged in any desired order.

At the left end of the device of Figure 2 is a rotary switch at adapted for manual operation, and this switch is in circuit with a battery Si or other source of current. There are six make contacts 92-93 on switch 96, and, if desired, a neutral The six make contacts are adapted for variable connection to the ten contacts it-5t, inclusive, by means of plugs and jacks, as 99, 99".

At the other end of the rotor system, ten output leads may be seen, and, associated with each, an electric lamp, as Nil-l it, inclusive, these lamps being likewise in the circuit of battery 9!. Adjacent the lamps is a strip i l i, bearing ten numerals randomly arranged. This strip is slidably mounted in a holder H2, so that it may be removed therefrom and replaced by another strip.

In the preferred embodiment of the invention, means are provided for stepping one or more of the rotors I l-fill each time a signal is fed through the system. In Figure 2, such means are represented by block 529. After positioning rotary switch 90, switch l2i, which may be in the nature of a simple pushbutton, is closed. When it is reopened, rotor H is advanced one step. The other rotors are stepped under the control of rotor H in any of several well-known manners.

Assuming switch l2l to be closed, it will be apparent that an electrical current from battery 9| will traverse a path through the rotor system depending, in the first instance, on the input contact utilized, and, secondly, upon the internal wiring of the several rotors, the order in which the rotors are arranged on shaft 35, and the relative rotatory positions of the rotors. Under one set of conditions, for example, a signal introduced at the contact 2 on the leftmost rotor of Figure 2 may find its way through the rotor maze to energize lamp H0. A change in any one of the conditions mentioned just above, may cause the signal to illuminate lamp Hit. The number on the strip Ill, adjacent the energized lamp, will depend upon the arrangement of the numerals on the strip.

One method of using the invention, by a, bank or other financial organization, will now be described. A United States bank, Wishing to make a deposit in a London bank, would compose the basic text of its cablegram according to the standard private code in use. It would then take the device of this invention and, in conformity with a prearranged plan, insert a particular strip III in the holder H2 and arrange the rotors in proper order. The contacts 92-91, inclusive, would next be plugged into predetermined input connectionsv in member 33. The rotors would then be individually adjusted so that, for example (reading the second row of indicia on the rotors), the first two would indicate the serial number of the message (35, in Figure 2), rotor '13 would indicate United States dollars, and rotors. "-80, the amount of the deposit ($9,756,125, in the illustration).

The operator would then move switch arm 90 to contact 9,2, for example, and under these circumstances it may be assumed that the lamp I02, adjacent numeral 1 on strip III, will be lighted. Arm 90 would then be moved to contact 93, and lamp Hll adjacent numeral 5 would be energized. Upon movement of arm 90 to contact 94, lamp H11, adjacent numeral 9, would be energized. The operator would take these three numerals in the Order inwhich they occurred, namely, 1-5-9, and encode them by means of thi standard code, thereby obtaining a group such as ROXEP. This group, located in a prearranged position in the message, would then be transmitted as an authenticator.

The bank receiving the cablegram would, after decoding, set up its machine just as the machine was set up by the transmitting bank, ar-

ranging the rotors in accordance with the amount of the deposit, the serial number of the message, etc. The operator would next move the switch arm 90 of his device to the three contacts 92-93- 9.4 in order. Unless he derived the number represented in his codebook by the group ROXIP, he would know that either the message was not authentic or that some error had been made.

Of course the device will not furnish a dif ferent code groupfor each possible condition of the rotors and other variable elements. Considering the seven rotors 104-410 alone, it will be apparent that ten million different combinations can be set up, whereas using the ten lamps, IDL H0, inclusive, in combinations of three, only 720 different test groups can be obtained. A greater number of groups can, of course, be achieved if it is desired to use longer test groups, but in ordinary business usage the three-numeral group has been found to be satisfactory.

Further, it will be obvious that either more or fewer rotors may be used, without altering the principles of the invention. The number decided upon will depend upon many factors.

The above descriptionv is in specific terms. It should be understood, however, that the invention is not limited to the exact structure shown and described, and, therefore, for the true scope of the invention, reference should be had to the appended claim.

I claim:

In a device of the nature described, a source of current, a series of crytographic motors having a plurality of inputs and a plurality of outputs, a selector adapted to make successive circuits between said source of current and a limited number of preselected inputs to said series, an indicator for each of said outputs adapted to be energized by said source, and means for assigning variable values to said indicators said means comprising a holding member adjacent said indicators and a card or the like slidably held thereby said card bearing indicia which may be variously juxtaposed with the said indicators.

WILLIAM F. FRIEDMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,58%660 Soherbius May 11, 1926 1,683,072 Hebern Sept. 4, 1928 1,938,628 Korn Dec. 5, 1933 1,953,829 Morris Apr. 3, 1934 2,080,416 Friedman May 18, 1937 2,139,676 Friedman Dec. 13, 1938

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