[image of digits]

Collections in Cryptology - Polyalphabetic Substitution Ciphers
Key mechanisms in computation...

These are semi-automated machines, providing the user with a different
pseudo-random alphabet for each character in the clear text.

KRYHA Cipher Machine (1924)
An Early Standard Model
Used by the German Diplomatic Corps through the 1950s.
There are 4.57 x 1050 possible key values.
Two versions side-by-side:
There is a crank to wind the mechanism which is inserted at the bottom right. The knob at the right activates the mechanism when it is pulled out. The button in the center advances the mechanism one step if briskly pressed.
The letters in the inner circle and outer arc may be moved to any desired position. The letters in the inner circle are usually set to repeat a mixed (or random) alphabet twice.

Outer cover closed. Outer half-circle is set in order.

Outer cover closed. Outer half-circle is set randomly.

Outer cover open. Inner circle and outer arc are fully visible.

Outer cover open. Inner circle and outer arc are fully visible.

Inner cover open. 17-step gray geared wheel is visible to the left.

Inner cover open. 17-step gray geared wheel is visible to the left.

Key to the Marconi version.

To set the machine:
Advance the gray toothed wheel to a predetermined red number (in this example "1"). Rotate the inner circle until the number "18" lines up with the number "18" on the outer arc.

To encript a message:
 Look up the first letter of the plaintext on the outer arc and select the adjacent letter on the inner circle as the first letter of the ciphertext. Briskly press the button and repeat for each letter.

To decripta message:
Advance the gray toothed wheel and rotate the inner circle to the previous settings. Look for the first letter of the ciphertext on the inner circle and select the adjacent letter on the outer arc as the first letter of the plaintext. Briskly press the button and repeat for each letter.

Decode this enciphered message:
 KXIIW GCQWF PS

Hagelin CD-57

A hand held unit used by the French Police (1965)


The alphabet in the outer circle may be penciled in or a decal may be applied. The decals above would provide the unit with two ordered alphabets - not a particularly good idea...

To set the machine:
Open the cover and remove the crank. With the cover closed and locked shut and the advancing lever pressed into the case and locked, insert the crank in the hole on the front panel and set the counter to zero. You may turn the crank either way.

To encript a message:
 Release the advancing lever. Look up the first letter of the plaintext on the outer circle and select the adjacent letter on the inner circle as the first letter of the ciphertext. Press and release the advancing lever and repeat for each letter.

To decript a message:
Set the machine to zero as described in the first paragraph above. Look for the first letter of the ciphertext on the inner circle and select the adjacent letter on the outer circle as the first letter of the plaintext. Press and release the advancing lever and repeat for each letter.
Swedish HC-9
A desktop unit requiring a punched paper card and a printed paper random alphabet.
The random alphabet is rotated according to the punched card each time a letter is to be encoded or decoded.