CLASS: 

SYSTE2h 

METHOD: 

NAME: 

REF ID:A27300B 

Cipher Machine (Electro-mechanical) 

Combined .Y.onographic Sub8titution and Siaple Tramlpo81tioa 

Two Circuit-Rotor Mazes, Through Paths, Gear Motion Con\rol 

. ·=-=--":"""::"" :--'.:.:-:-:":"" ' 

Koch Transposition-Substitution Cipher Machine 

DEVELOPMEN~ 

Invefl'l:r:'r. by H. !. Koch. Application for basic patent tiled 111 the 

Netherland;.;, ? October 1919. Assigned to Naamlooze Vennootschap Ingenieurwbureau "Se~ tas", Amsterdam, Netherland.a, a firm associated with 

Chiffrierm~~~C'.Lengesellschaft of Berlin, Who later denloped the 

"Enigma". '~r:•·,•r !DB.nufactured commercially. 

PATENTS: 

u. s. 1,533,252 (H. 1. Koch, 14 April 1925, Cl. 19?-4). One ot three 

pneumaticaJ• y operated machines described in this patent combines tranaposi tion a.~ substitution features. Will not decipher. 

Ger 3~ ,682 (Naamlooze Vennootschap Ing. Bureau "Securitas", 'Z'l Not'eaber 

1923, Cl. ~4•· 14). Improved electro .... echanical version of the machine deacribed in 1. S. Patent 1,533,252. 

nESCRIP'ITOI~-: 

A keyl•Mi u-operated, page-printing cipher machine which combines both 

subs ti tutiiou and transposition features. A transposition of characters within 

each line :J: printed text is accomplished by means of a circuit-rotor maH 

which contr:3._, the linear displacement of a typewheel relative to the pap on 

which ciph1··i· characters are printed. After the printing of a line of text 

(which mus:. be of a definite length, determined by the number of exit pointa 

from the ~~or maze), the rotors are stepped by a set of gap-toothed geare. 

The substU1F"C"'.ion process occurs in two phases. A given plain-text character 

is first en.,,t.i"\fu th.rough another set of circuit rotors which, like the 

transposi t:•••• rotors, are stepped at the end of each line of cipher text. 

It is then re-enciphered through one of a group of relay banks before being 

printed. i~et• selection of the particular relay bank used to accomplish thia 

super-enci?'m:nnent is detennined by the position within the line to which the 

character :-.: transposed. The ref ore, the first substitution is monoalphabetic 

within eac~ line and the second substitution is monoalphabetic in identical 

positions ~.!W:af~ the various lines of cipher text. To decipher, the direction 

of the ci~·~· t paths through both rotor mazes and through the relays must be 

reversed b! means of an encipher-decipher switching arrangement (not shown 

in the accc~·1='•:9lng drawing). 

In ord(::r to simplify the illustration, a machine with only six different 

characters and a line length of six has been shown. 'lhe keyboard universal 

bar has tw~ functions: When a key is depressed, this bar is activated, 

closing co!i'I~~~ (l); also, pawl (3) is caused to engage a tooth of the 

ratchet wh~ associated with commutator (4). Rigidly mounted on the aame 

shaft with this ratchet wheel are the brush-arm of the commutator am the 

single-too~. pinion (5). When the key is released, the universal bar 11 

returned t~ its normal position through spring action, contact (2) is broken, 

@'pp roved for Release by NSA on 09-12-2013 pursuantto E .0. 1352a 

~,-;/ "· ;; _ 

_ ·'. 

'f• 

~-· ... 

·----·-... ,,,, .... ___ ,_, ... , ~.~ .. ,~"';-. 

I 
( 

REF ID:A273008 

and the ratchet-wP.eel assembly is stepped forward one position, causing the 

brush-arm to move to the next segment of conmutator (4). Once during each 

revolution of the ratchet wheel, the single tooth of the pinion engages the 

cogwheel with which it is in register and the shaft carrying the gap-toothed 

gears is advanced one step. Through the action of these gears, the rotors 

in the two mazes are stepped irregularly. 

The relay unit consists of as many banks as there are exit points from 

the transposition maze, each bank having as many contacts as there are exit 

points frCJD the substitution maze. Current through a given lead from the 

transposition maze will energize one of the electromagnets (6), causing the 

bank of contacts associated with it to close. Current through another lead 

from the substitution maze will then be allowed to flow, via one of the 

closed circuits, to a segment of conunutator (lJ). The contacts of the 

various relay banks are connected to the output leads in different orders, 

as shown. 

The printing mechanism operates as follows: The typewheel is mounted on 

a four-sided shaft (12) along which it can slide laterally. This shaft is 

rotated continuously by a motor. Attached to the typewheel is a cylindrical 

aember (11) which fits over the shaft as a sleeve and on which a ring (10) is 

mounted so that, although it is fixed in position on the sleeve (11), the 

latter my rotate freely within it. Through the linkage shown, the lever (9) 

is capable of displacing the typewheel assembly laterally along the shaft (12). 

'When the magnet coil (8) is energized, its movable core is pulled in and the 

typewheel is moved to the le~; when it is de-energized, the typewheel is 

returned to its extreme right-hand position by spring action. When one of the 

magnet coils (7) is energized, its core is raised and the leftwa1'1 movement of 

the typewheel is blocked by the engagement of ring (10) with this projecting 

core. Brush-arm (14) is rigidly mounted on the square shaft (12) and as the 

latter rotates the brush-a:nn passes over the mutually insulated segments of 

commutator (lJ). When the brush-am reaches a conducting segment, current is 

transmitted to magnet coil (15) which, when energized, causes the platen to 

strike against the typewheel and so print the character associated with the 

seginent of commutator (13) thrrugh which current has passed. 

When a key is depressed, two circuits are completed successivelyi First, 

contact (1) is closed by the universal bar action and current flows from the 

positive pole of battery via commutator (4) through the transposition rotor 

maze to one of the magnets (6) which, when activated, closes the bank of relaf 

contacts associated with it; thence through the coil of one of the magnets (7) 

to coil (8) which i.nten.ct to displace the typewheel laterally as described 

above; and back to· n•gative battery. Then, immediately after the closing of 

cont.act (1), the contact (2) of the particular key depressed is closed and 

cu?Tent flmrs from battery via the substitution rotor maze to the relay banks 

and from there, through the path made available by the action of magnet (6), 

to a segment of commutator (1.3), from whence it is transmitted via brush-arm 

(14) to coil (15) and back to battery. . 

la described in the patent, variable keying elements include only the 

rotor order within the two mazes and the relaUn alignment of the rotors 

!or a particular aeange encryption. lfo provision is made for interchanging, 

replacing or otherwise vaeying the relationships among the gap-toothed gears, 

but. the ponibility of cbang:1.ng the circuit pat.ha through the different relay 

bulks b7 --.u or a pluging arranceraent 1a suggested. 

Notei.. IA tbe tlrat J*Wnt on thi• aacbine pneuutic instead o! electrical oi~ &N ued,, the relq buta baT9 been olli tted and the gears controlllnc 

ti. •tion ot ~ ~betitut.lon rot.on &r"e•atepped each time a lce7 is depreand, 

,. 

• 
REF ID:A27300B 

thus making decipherment in a single operation impossible. The inventor 

apparently overlooked the fact that it would be necessary first to replace 

the cipher characters in their proper order through the transposition maze, 

and then to decipher this correctly arranged sequence through the substitution maze in order to obtain the original plain text. In the later·patent, 

another version of the machine is described in which the relay banks are 

omitted and the stepping of one of the rotors in the substitution maze is 

controlled, through a rather crude wire ~nd pulley linkage, by the lateral 

movement of the typewheel assemblJ• Thus, the position to which the typewheel is displaced by the transposition unit determines the substitution 

alphabet used to encipher a given character • 

__ : ,,,._ «·--· ---'IMIL\1!!1£Jlllllllllll'l!lllSW_.#YI ·111!1~··' M.. f ,) .us: J . L UMllllJ\Wl!i iJ £ J jj •&J ££ JJ£ bi. l£iwil 
• 

\ 7 

-- •' .. ,. 

. : .. -..... 

-

REF ID:A27300B 

I.I

n /=·------·;~-~- .. ·------------T I ·-·---TL ··-·-,_4 1!5 

I I I j •--~· <:,------- .. 14 

~- '.Ci f'0:-i ( ,~~:-:::=- l _________ . /)' 

--· 

'°I', : I I 

: I ' 

I I 1 1 i1:.' 

I! I. 

:j: . 'I . ' ! : ··-4,.--.---. 

: I: 

. I 

·\··tf .'l.-l~ •I ~! ·' · 'TYPEWHEEL ,. t ·.{ 4:···1 '• =· '-- ·'i '· •• '. .l . I 

. J i . ; : . ! ! ~ '. 

---. .. ·-· .... t- ·--+ .... i i 

2 i :Y_J'·IJ; I :·~; 

. -··r--+-IL.J11.-·~'. · ... Ill. l.I< .... i ~j jl . ! I!: .. ll I:!. I. 

. ' 

: <! 

I . ' ·I 

; :·1 

I ~ l':j·I· _____ _, 1.11 .. , : -=,:..::=_~· 'l: 

UN IVER SAL BA"--~~""'."._-_.-.:--._-._---~-~-J-.-. 

-·~t;·-·-··· 

' i '. 

I 

'I: TRANSPOSITION MAZE 

·I: I i I' 1-· 

.I 

i !: I 

I 'I 

I

. i I, 

I ,i I. I 

j 

,_ 

---

8 ~ 

~~ 'E J ~r 

r- ,_ __ I 

I . 

Ii 

4 

~ ·' . i 

. _ .. -····-···- 11. r·····----

·--· 3 ; '1: iii • 1 I 

!! 5 ! SUBSTITUTION MAZE l j I 

,;::::r 

.~ _e,1, ,.-- J

;=:,_. 

,_, ~· 

.. l 

... . . ~ 

Rl~"y IAlllllS