CURIOSITIES OF CIPHER.
In 1680, when M. de Louvois was French Minister of War, he summoned before him one day, a gentleman named Chamilly, and gave him the following instructions:—
“Start this evening for Basle, in Switzerland, which you will reach in three days; on the fourth, punctually at two o’clock, station yourself on the bridge over the Rhine, with a portfolio, ink, and a pen. Watch all that takes place, and make a memorandum of every particular. Continue doing so for two hours; have a carriage and post-horses await you; and at four precisely, mount and travel night and day till you reach Paris. On the instant of your arrival, hasten to me with your notes.”
De Chamilly obeyed; he reaches Basle, and on the day, and at the hour appointed, stations himself, pen in hand, on the bridge. Presently a market-cart drives by, then an old woman with a basket of fruit passes; anon, a little urchin trundles his hoop by; next an old gentlemen in blue top-coat jogs past on his gray mare. Three o’clock chimes from the cathedral-tower. Just at the last stroke, a tall fellow in yellow waistcoat and breeches saunters up, goes to the middle of the bridge, lounges over, and looks at the water; then he takes a step back and strikes three hearty blows on the footway with his staff. Down goes every detail in De Chamilly’s book. At last the hour of release sounds, and he jumps into his carriage. Shortly before midnight, after two days of ceaseless traveling, De Chamilly presented himself before the Minister, feeling rather ashamed at having such trifles to record. M. de Louvois took the portfolio with eagerness, and glanced over the notes. As his eye caught the mention of the yellow-breeched man, a gleam of joy flashed across his countenance. He rushed to the king, roused him from sleep, spoke in private with him for a few moments, and then four couriers, who had been held in readiness since five on the preceding evening, were dispatched with haste. Eight days after the town of Strasbourg was entirely surrounded by French troops, and summoned to surrender; it capitulated and threw open its gates on the 30th September, 1681. Evidently the three strokes of the stick given by the fellow in yellow costume, at an appointed hour, were the signal of the success of an intrigue concerted between M. de Louvois and the magistrates of Strasbourg, and the man who executed this mission was as ignorant of the motive as was M. de Chamilly of the motive of his errand.
Now this is a specimen of the safest of all secret communications; but it can only be resorted to on certain rare occasions. When a lengthy dispatch is required to be forwarded, and when such means as those given above are out of the question, some other method must be employed. Herodotus gives us a story to the point; it is found also, with variations, in Aulus Gellius:—
“Histiæus, when he was anxious to give Aristagoras orders to revolt, could find but one safe way, as the roads were guarded, of making his wishes known; which was by taking the trustiest of his slaves, shaving all the hair from off his head, and then pricking letters upon the skin, and waiting till the hair grew again. This accordingly he did; and as soon as ever the hair was grown, he dispatched the man to Miletus, giving him no other message than this: ‘When thou art come to Miletus, bid Aristagoras shave thy head, and look thereon.’ Now the marks on the head were a command to revolt.”—(Bk. V. 35.)
Is this case no cipher was employed. We shall come now to the use of ciphers.
When a dispatch or communication runs great risk of falling into the hands of the enemy, it is necessary that its contents should be so veiled that the possession of the document may afford him no information whatever. Julius Cæsar and Augustus used ciphers, but they were of the utmost simplicity, as they consisted merely in placing D in the place of A; E in that of B and so on; or else in writing B for A, and C for B, &c.
Secret characters were used at the Council of Nicæa; and Rabanus Maurus, Abbot of Fulda and Archbishop of Mayence, in the Ninth Century, has left us an example of two ciphers, the key to which was discovered by the Benedictines. It is only a wonder that any one could have failed to unravel them at the first glance. This is a specimen of the first:—
.Nc.p.tv:rs:.:sB::nf:c..:rch.gl::r::s.q:.::m:
rt.r.s
The clue to this is the suppression of the vowels and the filling of their places by dots—one for i, two for a, three for e, four for o, and five for u. In the second example, the same sentence would run—Knckpkt vfrsxs Bpnkfbckk, &c., the vowel places being filled by the consonants—b, f, k, p, x. By changing every letter in the alphabet, we make a vast improvement on this last; thus, for instance, supplying the place of a with z, b with x, c with v, and so on. This is the very system employed by an advertiser in a provincial paper, which we took up the other day in the waiting-room of a station, where it had been left by a farmer. As we had some minutes to spare, before the train was due, we spent them in deciphering the following:—
Jp Sjddjzbrza rzdd ci sijmr. Bziw rzdd xrndzt, and in ten minutes we read: “If William can call or write, Mary will be glad.”
When the Chevalier de Rohan was in the Bastile his friends wanted to convey to him the intelligence that his accomplice was dead without having confessed. They did so by passing the following words into his dungeon written on a shirt: “Mg dulhxecclgu ghj yxuj; lm et ulge alj.” In vain did he puzzle over the cipher, to which he had not the clue. It was too short; for the shorter a cipher letter, the more difficult it is to make out. The light faded, and he tossed on his hard bed, sleeplessly revolving the mystic letters in his brain; but he could make nothing out of them. Day dawned, and with its first gleam he was poring over them; still in vain. He pleaded guilty, for he could not decipher “Le prisonnier est mort; il n’a rien dit.”
A curious instance of cipher occurred at the close of the sixteenth century, when the Spaniards were endeavoring 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 cipher, which they varied from time to time, in order to disconcert those who might attempt to pry into the mysteries of their correspondence. The cipher, 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 dispatches 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, Herman, who boasted, in 1752, that he had discovered a cryptograph absolutely incapable of being deciphered without the clue being given 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. The cipher—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; the 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 cipher is astonishing.
All these cryptographs consist in the exchange of numbers of 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,
Recommande a Monsieur
le Comte de Vergennes, par le Marquis de Puysegur, Ambassadeur
de France a la Cour de Lisbonne.
The card told more tales than the words written on it. Its color indicated the nation of the stranger. Yellow showed him to be English; red, Spanish; white, Portuguese; green, Dutch; red and white, Italian; red and green, Swiss; green and white, Russian; &c. The person’s age was expressed by the shape of the card. If it were circular, he was under 25; oval, between 25 and 30; octagonal, between 30 and 45; hexagonal, between 45 and 50; square, between 50 and 60; an oblong showed that he was over 60. Two lines placed below the name of the bearer indicated his build. If he were tall and lean, the lines were waving and parallel; tall and stout, they converged; and so on. The expression of his face was shown by a flower in the border. A rose designated an open and amiable countenance, whilst a tulip marked a pensive and aristocratic appearance. A fillet round the border, according to its length, told whether he were bachelor, married, or widower. Dots gave information as to his position and fortune. A full stop after his name showed that he was a Catholic; a semicolon, that he was a Lutheran; a comma, that he was a Calvinist; a dash, that he was a Jew; no stop indicated him an Atheist. So also his morals and character were pointed out by a pattern in the card. So, at one glance the Minister could tell all about his man, whether he were a gamester or a duelist; what was his purpose in visiting France; whether in search of a wife or to claim a legacy; what was his profession—that of physician, lawyer, or man of letters; whether he were to be put under surveillance or allowed to go his way unmolested.
We come now to a class of cipher which requires a certain amount of literary dexterity to conceal the clue.
During the Great Rebellion, Sir John Trevanion, a distinguished cavalier, was made prisoner, and locked up in Colchester Castle. Sir Charles Lucas and Sir George Lisle had just been made examples of, as a warning to “malignants:” and Trevanion had every reason for expecting a similar bloody end. As he awaits his doom, indulging in a hearty curse in round cavalier terms at the canting, crop-eared scoundrels who hold him in durance vile, and muttering a wish that he had fallen, sword in hand, facing the foe, he is startled by the entrance of the jailor, who hands him a letter:
“May’t do thee good,” growls the fellow; “it has been well looked to before it was permitted to come to thee.”
Sir John takes the letter, and the jailor leaves him his lamp by which to read it:—
Worthie Sir John:—Hope, that is ye best comport of ye afflictyd, cannot much, I fear me, help you now. That I wolde saye to you, is this only: if ever I may be able to requite that I do owe you, stand not upon asking of me. ’Tis not much I can do; but what I can do, bee verie sure I wille. I knowe that, if dethe comes, if ordinary men fear it, it frights not you, accounting it for a high honour, to have such a rewarde of your loyalty. Pray yet that you may be spared this soe bitter, cup. I fear not that you will grudge any sufferings; only if it bie submission you can turn them away, ’tis the part of a wise man. Tell me, an if you can, to do for you any thinge that you would have done. The general goes back on Wednesday. Restinge your servant to command.
R. T.
Now this letter was written according to a preconcerted cipher. Every third letter after a stop was to tell. In this way Sir John made out—“Panel at east end of chapel slides.” On the following even, the prisoner begged to be allowed to pass an hour of private devotion in the chapel. By means of a bribe, this was accomplished. Before the hour had expired, the chapel was empty—the bird had flown.
An excellent plan of indicating the telling letter or words is through the heading of the letter. “Sir,” would signify that every third letter was to be taken; “Dear Sir,” that every seventh; “My dear sir,” that every ninth was to be selected. A system, very early adopted, was that of having pierced cards, through the holes of which the communication was written. The card was then removed, and the blank spaces filled up. As for example:—
My dear X.—[The] lines I now send you are forwarded by the kindness of the [Bearer], who is a friend. [Is not] the message delivered yet [to] my brother? [Be] quick about it, for I have all along [trusted] that you would act with discretion and dispatch.
Yours ever, Z.
Put your card over the note, and through the piercings you will read: “The Bearer is not to be trusted.”
Poe, in his story of “The Gold Bug,” gives some valuable hints on the interpretation of the most common cryptographs. He contends that the ingenuity of man can construct no enigma which the ingenuity of man cannot unravel. And he actually read several very difficult ciphers which were sent to him after the publication of “The Gold Bug.”
But we saw, several years ago, a method which makes the message absolutely safe from detection. We will try to describe it.
Take a square sheet of paper of convenient size, say a foot square. Divide it by lines drawn at right angles into five hundred and seventy-six squares, twenty-six each way; in the upper horizontal row write the alphabet in its natural order, one letter in each square; in the second horizontal row write the alphabet, beginning with B. There will then be one square left at the end of this row; into this put A. Fill the third row by beginning with C, and writing A and B after Z at the end. So on until the whole sheet is filled. When completed, the table, if correct, will present this appearance. In the upper horizontal row, the alphabet in its natural order from left to right; in the left-hand vertical row, the same from top to bottom; and the diagonal, from upper right to lower left-hand corner, will be a line of Z’s.
Each party must have one of the tables. A key-word must be agreed upon, which may be any word in the English language, or from any other language if it can be represented by English letters, or, indeed, it may even be a combination of letters which spells nothing.
Now, to send a message, first write the message in plain English. Over it write the key-word, letter over letter, repeating it as many times as it is necessary to cover the message. Take a simple case as an illustration. Suppose the key-word to be Grant, and the message We have five days’ provisions. It should be placed thus:—
Grantgrantgrantgrantgran
Wehavefivedaysprovisions
Now find, in the upper horizontal row of the table, the first letter of the key-word, G, and in the left-hand vertical column, the first letter of the message, W. Run a line straight down from G, and one to the right from W, and in the angle where the two lines meet will be found the letter which must be written as the first letter of the cipher. With the second letter of the key-word, R, and the second letter of the message, E, find in the same way the second letter of the cipher.
The correspondent who receives the cipher goes to work to translate it thus:—He first writes over it the key-word, letter over letter, repeating it as often as necessary. Then finding in the upper row of his table the first letter of the key-word, he passes his pencil directly down until he comes to the first letter or the cipher; the letter opposite to it in the left vertical column is the first letter of the translation. Each of the succeeding letters is found in a similar way.
A third party, into whose hands such a cipher might fall, could not read it, though he possessed a copy of the table and knew how to use it, unless he knew the key-word. The chance of his guessing this is only one in millions. And there is no such thing as interpreting it by any other method, because there are no repetitions, and hence all comparison is at fault. That is to say, in the same cipher, in one place a letter, as for instance C may stand for one letter in the translation, and in another place C may stand for quite a different letter. This is the only kind of cryptograph we have ever seen which is absolutely safe.