Codes and Ciphers: Secret writing through the ages

the whole system, but this is not necessarily true of a code. Every navy uses codes. A code, because of its nature, poses tremendous problems for the enemy cryptanalyst and if he should partially obtain the solution, he is still no nearer solving the rest of the message. The limitations of a code book do not bother the Navy, for there is only a limited number of things a ship can be ordered to do. Armies, however, use ciphers. Except for stationary or nearly stationary units, such as Army H.Q., army units cannot conveniently carry code dictionaries around with them, and, if they did, they might easily lose them to the enemy before they could be destroyed. Warships have no such problem. Their code books are bound in lead, so that when thrown overboardif cap- ture appears imminentthey will sink at once. Diplomats use both codes and ciphers, but prefer ci- phers because they are more flexible and can express fine shades of meaning. Secret agents prefer codes because they can express more or less space, and a long message is dangerous to a spy. They prefer to give the impression that no message at all is being sent, hence the invention of invisible ink. Criminals nearly always use ciphers, usually because the standard code books do not contain the particular phrases they want to use. Probably the safest way of sending a message is to en- cipher a coded message. This double concealment could tax the ingenuity of even the most gifted cryptanalyst. Cryptography is an extremely old art. In ancient days, the ordinary written language was really secret writing, for CODES and CIPHERS defeat can be laid on the cryptographers. Throughout the war they served their country well, as cryptographers of all nations have done. The Germans were true to a long tradition. An individual drastically affected by ciphers was the Chevalier Rene de Rohan who, in 1674, commanded the French tov^m of Quilleboeuf on the Dutch frontier. The Chevalier frequently boasted of his ability with ciphers. He could break any cipher, he claimed, although genuine experts never boast about their skill; sometimes a simple cipher is difficult to break. But de Rohan was a braggart, and worse, he was a traitor. N, R, T. Find these letters on the outer circle and note down their opposite letters on the inner circleb, g, c, a.