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.
The Reason Why.
WHY THE GERMANS EAT SAUER-KRAUT.
The reason why the most learned people on earth eat sauer-kraut may be found in the following extract from a work entitled Petri Andreæ Matthioli Senensis medici commentarii in sex libros Pedacii Dioscoridis de Materiâ Medica. Venetiis. ex officina Valgrisiana MDLXV. Traduit de Latin en Francais, par M. Antoine du Pinot. Lyon, MDCLV. Preface, p. 13. ligne 30: “Finally, in order to omit nothing which can add to the knowledge of simples, it must be noted that Nature, mother and producer of all things, has created various simples, which have a sympathy or natural antipathy to each other; which is a very considerable point in this matter, and has no like as a mystery and secret. And thus it has seemed to me good to hint a word about it, and principally of those which are used in medicine. To commence, then, with the oak and the olive; these two trees hate each other in such sort that, if you plant one in the hole from which the other was dug, it will die there; and, even if you plant one near the other, they will work each other’s death. The cabbage and the vine do the like; for it has been seen that, if you plant a cabbage at the foot of a vine, the vine will recoil and draw itself away. And thus it is no marvel that the cabbage is very useful to sober topers, and that the Germans eat it commonly in a compost to safeguard themselves from their wine.”