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From FLYNN's April 25, 1925


Edited by M. E. Ohaver

THIS department bowls merrily along, making new friends at every turn. So great has been the response, and so urgent the demand for more and harder problems, that we are hiding this week's cipher. You have to find it before you can solve it. And you have to work after you have found it.

At the risk of disappointing some of you, FLYNN'S is obliged to postpone the publication of the names of successful cryptographers. You will find the reason on the last page.

So speed up with Mr. Ohaver. Dig into this article and find the cipher. Solve it if you can. And watch FLYNN'S for the correct solution to see if your own tallies.

SERIES of articles on cryptography that does not include the famous biliteral cipher of Sir Francis Bacon, English philosopher, statesman, and essayist, would be like a detective story with one of the most important chapters missing.

Bacon's cipher is one of the most widely known in all the literature of cryptography. And its fame is not merely a reflection of that of its illustrious inventor, for the cipher is, in itself, one of superlative merit and of wide adaptability.

In the latter part of 1576, Bacon was sent abroad with Sir Amyas Paulet, the English ambassador at Paris. Political and social conditions in France were greatly disturbed at this period, and Bacon, thrown into the thick of court intrigue, rapidly acquired valuable experience in governmental affairs.

He soon saw the need of a secure and easily used method of secret writing that would be free of suspicion. And accordingly it was only about two years after his arrival in Paris, when he was still but a youth of seventeen years, that he conceived the idea of his biliteral cipher.

Presumably he reserved this remarkable device for use with none but his most intimate friends. At any rate, in 1609 he sent the key to this cipher, with request for strictest secrecy, to his friend and correspondent, Sir Tobie Matthew, at that time in Madrid during his long exile from England.

It was not until three years before his death that Bacon preserved this cipher to the world by including a full account of it in the 1623 edition of his Advancement of Learning . In this work the various branches of knowledge are discussed and classified, ciphers being included under the Division of Speech, and further relegated to the Department of Writing.

The biliteral cipher is one of the double substitution type; that is, a message is enciphered by two successive processes of substitution. The first substitution is by means of a biliteral—two-letter—alphabet, and the second by a bi-formed alphabet.

The biliteral alphabet consists of various combinations of the letters a and b taken in groups of five, each group representing a letter of the alphabet. Two characters permuted through five places produce thirty-two combinations, only twenty-four of which were required for the English alphabet of Bacon's time, when the letters I and J , and U and V, were used interchangeably. The remaining eight groups Bacon made no use of.

A=aaaaa I-J=abaaa R=baaaa Not
B=aaaab K=abaab S=baaab bbaab
C=aaaba L=ababa T=baaba bbaba
D=aaabb M=ababb U-V=baabb bbabb
E=aabaa N=abbaa W=babaa bbbaa
F=aabab O=abbab X=babab bbbab
G=aabba P=abbba Y=babba bbbba
H=aabbb Q=abbbb Z=babbb bbbbb

 In the biformed alphabet each letter is assigned two different forms or shapes. These differences may be so small as to elude all but the closest inspection, or even so minute as to necessitate the use of a magnifying glass to detect them.

 In the examples given herewith, however, the two forms are expressed by Roman and Italic types, in order to minimize the difficulty of distinguishing between them.

But the biliteral cipher is not limited in its use to written or printed letters alone. It can be expressed by anything capable of being interpreted by any of the senses as possessing two differences, such as bells, trumpets, fireworks, cannon, et cetera.

The Morse telegraph alphabet—1838—is only an application of this principle to the two differences, the dot and the dash.

And the more modern printing telegraph alphabets follow Bacon's idea even more closely, the letters consisting of groups of five positive (p) and negative (n) electrical impulses. In the Western Union alphabet, for example: A=ppnnn; B=pnnpp; C=npppn; and so on.

To illustrate the commonest method of using the biliteral cipher, suppose it is desired to enfold the secret message “Stay” in the external and supposedly innocent writing, “Do not fail to leave at once.”

And suppose, further, that it is decided to use a Roman font of type for the a characters, and an Italic font for 6 characters.

The first step is to substitute for the letters of the internal writing at (1) the corresponding five-letter groups of the biliteral alphabet, at (2) . The external writing is next divided, as at (3) , into groups of five letters each, which correspond letter for letter to the groups in line (2) Roman letters being used for a characters and Italics for b characters.

Finally, at (4) , is shown the completed cipher, upon receipt of which the correspondent only needs to divide it into groups of five, substitute a or 6 for the Roman or Italic letters, and then decipher by means of the biliteral alphabet.

(1) S T A Y
(2) baaab baaba aaaaa babba
(3) Donot failt oleav eaton ce.
(4) Do not fail to leave at once.
In deciphering the biliteral cipher without the key, the biformed alphabets can usually be determined with little difficulty, owing to the fact that one of the forms of any given character, letter, or alphabet, will ordinarily predominate to some extent over the other.

If the original Bacon biliteral alphabet has been used, calculations have shown that the letters or characters of the “a” alphabet will outnumber those of the “b” alphabet approximately two to one; or, to be more exact, an average of 64.1 per cent of the total number will belong to the “a” alphabet, and 35.9 per cent to the “b” alphabet.

A count of the letters in the above short example will show how closely this rule works in practice, there being thirteen Roman letters to seven Italics, disregarding, of course, the nonessential letters at the end of the message.

The above short cipher, by concealing a single word in a short sentence, demonstrates that it is perfectly feasible to include a piece of writing of any length whatever in any other piece of writing five times as long.

 And in this connection must be mentioned the theory of Mrs. Elizabeth Wells Gallup, to the effect that the Bacon biliteral cipher was actually incorporated into the 1623 folio edition of Shakespeare's works, and other books of the same period.

In her work, the Bi-literal Cypher of Sir Francis Bacon, first published in 1899, she further claims to have really deciphered from the pages of these old books a great mass of material written by Bacon himself, including whole dramas, statements that Bacon is the real author of the works attributed to Shakespeare and other contemporary writers, and, further, a secret history of Bacon's life, that completely upsets the accepted records.

Of the many ciphers claimed to have been found in the works of Shakespeare, this one of Mrs. Gallup's is, in every way, the most plausible. And yet, to state the case impartially, there are many who doubt the existence of her cipher. The most serious obstacle in the way of the acceptance of her theory seems to be that no one else has succeeded in duplicating her results.

Exacting tests seem to show that different shapes of types were actually used intermixedly; but such use was apparently not in conformation with Bacon't original alphabet, as given above, nor in the manner that Mrs. Gallup contended. Thus one of the most amazing and baffling mysteries in all the annals of cryptography still appears to await a definite solution.

 Bacon's biliteral cipher has been called the most dangerous cipher ever invented. Almost anything may become its vehicle of expression, and it may lurk where its presence is least suspected. As Bacon himself put it, it is capable of signifying omnia per omnia (anything by everything), the only restrictions being that the including matter is capable of two differences, and of five times the length of the included matter.

To illustrate how insidious this cipher is, somewhere within the limits of this department you will find another biliteral cipher that has been made to conceal the name of a well-known celebrity.

 Let us sketch a hypothetical case showing the value of such a cipher in this last mentioned example. Suppose a man wounded to death by an enemy. Before dying he succeeds in concealing the name of his slayer in biliteral cipher. His foes are unable to .spot the clew.

But the keener intellect of a Craig Kennedy or of a Sherlock Holmes, versed in all branches of criminology, including cryptography, soon discerns the cipher, and apprehends the murderer.

See if you can find this cipher, and decipher the name it conceals. Like the purloined letter in Poe's tale, its hiding place may be so obvious as to escape your attention. Therefore, in your search, consider this friendly bit of advice: suspect everything, and overlook nothing.



 If you succeeded in discovering the keyword to the Nihilist cipher in the last article, you probably had no great trouble in unlocking the cipher itself.

You will remember that you were given the series of numbers: 42-63-108-66-66-86, with the statement that it was the key, in Nihilist cipher, enciphered by means of itself as a key. Any word so enciphered in this system will have the number for each letter added to itself, thus being exactly double the number of the letter it represents.

Halving the numbers in the above series gives the new series: 21-31-54-33-33-43— consequently the keyword: F-L-Y-N-N-S.

It is then only required to apply these numbers in accordance with the detailed instructions in the last article, as shown below, to decipher the message:

Cipher: 45-52-108-67-78-95-45-62-85, etc.
Key: 21-31-54-33-33-43-21-31-54, etc.
  —— —— —— —— —— —— —— —— —— 
Differences: 24-21-54-34-45-52-24-31-31, etc.
Message: I  F  Y  O  U  W  I  L  L, etc.

Here is the message completely deciphered:


Now is your chance to try your skill at puzzling the puzzler.

SOLVING CIPHER SECRETS has been such a success and there is such an increasing demand for it that we are speeding up the publication of the department. Owing to the mechanical necessity of printing a long time in advance we are compelled to close this issue before we have had time to hear from the successful strugglers with the cipher in that issue. However, we can make, amends later.

Readers of this department are asked to anticipate a special treat in the next article, in the form of a genuine World War cipher of great importance. Watch for it!



The first response to our offer to solve the Nihilist cipher came from far off Oklahoma just as this department was going to press.

Here it is:

Pawhuska, Okla.


In “our” magazine for March 28 you say, “If you will send a cryptogram written in Nihilist cipher to the editor of this department, he will endeavor to decipher it for you without the key word.”

All right, try this:


Surely brain sprainers are lots of fun. Keep them coming.

Yours truly,


We have found her key-word and solved her cipher. And it was so much fun that we are going to pass it on to you unsolved. You will find it a lot more intriguing and a lot more difficult when you are offered not even a hint as to the key-word.