The Sphinx
Now to turn to more scientifically constructed ciphers, such as have been employed by various Governments in correspondence with their ambassadors and secret servants.
The Sphinx Cipher, shown in [Fig. 11], is based upon a key-word of six or seven letters, previously arranged by the parties concerned A key-alphabet is written in full at the top of the plan, and against each letter of the key-word a complete alphabet is written as shown in the figure.
| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | |
| B | b | c | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z | a |
| A | c | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z | a | b |
| L | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z | a | b | c |
| F | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z | a | b | c | d |
| O | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z | a | b | c | d | e |
| U | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z | a | b | c | d | e | f |
| R | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z | a | b | c | d | e | f | g |
Fig. 11.—A Government cipher, called the “Sphinx.”
Suppose that the key-word chosen is BALFOUR, and that the message to be sent is WAR DECLARED LEAVE NOW, the key-word is then applied to the message thus:—
| W | A | R | D | E | C | L | A | R | E | D | L | E | A | V | E | N | O | W | . | |||
| B | A | L | F | O | U | R | B | A | L | F | O | U | R | B | A | L | F | O | . |
You then find in the top row the first letter of your message, which is W, and you see that the letter on a line with B and under W is X, which will be the first letter of your cipher. You then find A above and A by the side, which will give you C. You then find R above, and in the L horizontal column is its equivalent U. Proceeding thus with your message you arrive at the cipher, which reads: XCU HJISBTHH QKHWG QSB.
To read this it is only necessary to write the key-word under the cipher and reverse the proceeding.
An ingenious cipher, used by the War Office of a well-known Continental Power, is partially shown in [Fig. 12].
On two adjacent sides of a square entire alphabets are written, commencing at any letter (in the figure they begin at K in one and S in the other). Against each letter of the perpendicular alphabet the entire twenty-six letters are written horizontally, beginning with A and continuing in order. Leaving the first of these horizontal alphabets simple, against the remaining twenty-five, small alphabets are written as you will see in the figure, which shows the plain alphabets and five letters so treated.
| K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | |
| S | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
| T | Aa | Ba | Ca | Da | Ea | Fa | Ga | Ha | Ia | Ja | Ka | La | Ma | Na | Oa | Pa | Qa | Ra | Sa | Ta | Ua | Va | Wa | Xa | Ya | Za |
| U | Ab | Bb | Cb | Db | Eb | Fb | Gb | Hb | Ib | Jb | Kb | Lb | Mb | Nb | Ob | Pb | Qb | Rb | Sb | Tb | Ub | Vb | Wb | Xb | Yb | Zb |
| V | Ac | Bc | Cc | Dc | Ec | Fc | Gc | Hc | Ic | Jc | Kc | Lc | Mc | Nc | Oc | Pc | Qc | Rc | Sc | Tc | Uc | Vc | Wc | Xc | Yc | Zc |
| W | Ad | Bd | Cd | Dd | Ed | Fd | Gd | Hd | Id | Jd | Kd | Ld | Md | Nd | Od | Pd | Qd | Rd | Sd | Td | Ud | Vd | Wd | Xd | Yd | Zd |
| X | Ae | Be | Ce | De | Ee | Fe | Ge | He | Ie | Je | Ke | Le | Me | Ne | Oe | Pe | Qe | Re | Se | Te | Ue | Ve | We | Xe | Ye | Ze |
Fig. 12.—Another Government cipher—still in use.
The cipher is used in this way. The letters in each word of the message are divided into couples. These couples are found in the doubled alphabets in the center of the cipher scheme, and the key letters at the side and top show the actual cipher equivalent.
Suppose it is desired to put into this cipher the words CABLE CODE. Dividing the letters into couples CA, BL, E. CO, DE are obtained. Finding the combination CA it is simple to ascertain that the index letters are TM, which is therefore the cipher. BL is EL, whilst the remaining letter E from the top alphabet is found to be SO. Treating the word CODE in the same way the ciphers prove to be HM, XN, and therefore the message is transmitted thus: TMELSO HMXN.
So far an idea has been given of the systems of cipher from the simplest methods to the most complicated of political cryptograms. Although the actual details are necessarily hidden, it may be assumed as a positive fact that the most secret political ciphers now in use by civilized Governments are but adaptations of one or other of the methods described.