R D E
B C F
L M O
and for R we substitute E, and for O we substitute L.
Substituting our whole message by this system, it reads:
Original DE ST RO YB RI DG EA TO NC EX
Cipher EG TU EL XC AB EA GR UM IF RZ
As telegraph operators are accustomed to send these gibberish messages in groups of five letters (so that they can check errors, knowing that when only four appear in a group, for example, something has been left out) these enciphered groups of twos are now combined into groups of fives, so that the finished cipher reads:
EGTUE LXCAB EAGRU MIFRZ
The foregoing looks extremely complicated, but the truth is that anybody, after half an hour’s practice, can put a message into this kind of cipher (“Playfair” cipher) almost as fast as he can print the straight English of it in capital letters. And unless the person who reads it knows the key word which determined the pattern on his keyboard, he would have to be an expert to decipher it, and even he could do it only after a good deal of work.
Another ingenious cipher is called the “Chess Board.” First, a sheet of paper is ruled into squares exactly like a chess board—that is, a square divided into eighths each way. This arrangement gives, of course, sixty-four small squares. Then, by agreement between the people who intend to use this cipher, sixteen of these squares are agreed upon and are cut out of the sheet with a knife. Suppose, for example, this pattern is chosen:
and the squares showing in white are cut out.