Books: HOW TO SOLVE A CIPHER

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GJXXNGGOTZNUCOTWMOHYJTKTAMTXOB e in ea in ith n no n i

Now it becomes possible to find familiar words in plain English. For example, the letters ith appear near the beginning. Guessing that this could stand for with, the analyst assumes that M = w. He tries that idea out in other places where M appears in the ciphertext. Down the line this produces the sequence with-n-nown. This suggests: with unknown, in which case J would equal u, and K would equal k.

By now, the only two high-frequency plaintext letters remaining are r and s. Assume that F stands for r and G for s. If this is so, then the first nine letters in the message would read:

GJXXNGGOT su e s s i n

From this, success in leaps to mind, meaning that X — c. Each clue begets new clues until the cipher is solved. The cryptogram reads:

"Success in dealing with unknown ciphers is measured by these four things in the order named: perseverance, careful methods of analysis, intuition, luck. The ability at least to read the language of the original text is very desirable but not essential." Such is the opening sentence of Parker Hitt's Manual for the Solution of Military Ciphers.