Now suppose that I want to write England; I look among the small letters in the foregoing table for e, and find that it is in a horizontal line with b, and vertical line with b, so I write down Bb; n is in line with a and e, so I put down ae; continue this, and England will be represented by Bbaeacbdaaaeab. Two letters to represent one is not over-tedious: but the scheme devised by Lord Bacon is clumsy enough. He represented every letter by permutations of a and b; for instance,
A was written aaaaa, B was written aaaab
C was„ written„ aaaba, D was„ written„ aabaa
A much simpler method is the following. The sender and receiver of the communication must be agreed upon a certain book of a specified edition. The despatch begins with a number; this indicates the page to which the reader is to turn. He must then count the letters from the top of the page, and give them their value numerically according to the order in which they come; omitting those which are repeated. By these numbers he reads his despatch. As an example, let us take the beginning of this article: then, I=1, n=2, w=3, h=4, e=5, m=6, d=7, l=8, u=9, v=10, o=ll, omitting to count the letters which are repeated. In the middle of the communication the page may be varied, and consequently the numerical significance of each letter altered. Even this could be read with a little trouble; and the word “impossible” can hardly be said to apply to the deciphering of cryptographs.
A curious instance of this occurred at the close of the sixteenth century, when the Spaniards were endeavouring to establish relations between the scattered branches of their vast monarchy, which at that period embraced a large portion of Italy, the Low Countries, the Philippines, and enormous districts in the New World. They accordingly invented a cypher, which they varied from time to time, in order to disconcert those who might attempt to pry into the mysteries of their correspondence. The cypher, composed of fifty signs, was of great value to them through all the troubles of the “Ligue,” and the wars then desolating Europe. Some of their despatches having been intercepted, Henry IV. handed them over to a clever mathematician, Viete, with the request that he would find the clue. He did so, and was able also to follow it as it varied, and France profited for two years by his discovery. The court of Spain, disconcerted at this, accused Viete before the Roman court as a sorcerer and in league with the devil. This proceeding only gave rise to laughter and ridicule.
A still more remarkable instance is that of a German professor, Hermann, who boasted, in 1752, that he had discovered a cryptograph absolutely incapable of being deciphered, without the clue being giving by him; and he defied all the savants and learned societies of Europe to discover the key. However, a French refugee, named Beguelin, managed after eight days’ study to read it. This cypher—though we have the rules upon which it is formed before us—is to us perfectly unintelligible. It is grounded on some changes of numbers and symbols; numbers vary, being at one time multiplied, at another added, and become so complicated that the letter e, which occurs nine times in the paragraph, is represented in eight different ways; n is used eight times, and has seven various signs. Indeed the same letter is scarcely ever represented by the same figure; but this is not all: the character which appears in the place of i takes that of n shortly after; another symbol for n stands also for t. How any man could have solved the mystery of this cypher is astonishing.
Now let us recommend a far simpler system, and one which is very difficult of detection. It consists of a combination of numbers and letters. Both parties must be agreed on an arrangement such as that in the second line below, for on it all depends.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| 4 | 7 | 2 | 9 | 1 | 10 | 5 | 3 | 6 | 8 |
Now in turning a sentence such as “The army must retire” into cypher, you count the letters which make the sentence, and find that t is the first, h the second, f the third, a the fourth, r the fifth, and so on. Then look at the table. t is the first letter; 4 answers to 1; therefore write the fourth letter in the place of t; that is a instead of t. For h the second, put the seventh, which is y; for e, take the second, h. The sentence will stand “Ayh utsr emay yhutser.” It is all but impossible to discover this cypher.
All these cryptographs consist in the exchange of numbers or characters for the real letters; but there are other methods quite as intricate, which dispense with them.
The mysterious cards of the Count de Vergennes are an instance. De Vergennes was Minister of Foreign Affairs under Louis XVI., and he made use of cards of a peculiar nature in his relations with the diplomatic agents of France. These cards were used in letters of recommendation or passports which were given to strangers about to enter France: they were intended to furnish information without the knowledge of the bearers. This was the system. The card given to a man contained only a few words, such as:
ALPHONSE D’ANGEHA.
Recommandé à Monsieur
le Comte de Vergennes, par le Marquis de Puysegur,
Ambassadeur de France à la Cour de Lisbonne.
