The Null Cipher

How do you like your sample tasting of classical cryptography so far? You say that you had no idea that there were so many variables involved? You had no idea that your parents were so smart? You ask what happened to all that fun stuff that we used to do before things got a bit more complicated.

Well, let’s take a breather and get another look at some more of the fun stuff.  We’re going to look at another type of cipher (there are literally hundreds of different cipher types) in this chapter called the Null Cipher.  (I can see my fellow ACA members wincing as I define the Null Cipher as fun stuff. Not all of them feel that the Null is great fun.)

The Null Cipher is used by its practitioners to conceal the very existence of a cipher. The only cipher that cannot be solved is the one that no one knows exists. The plaintext is disguised by words looking every bit the same as ordinary text. But a key (there’s that word again) allows the reader to extract the plaintext from the disguised text.

Some portion of the ciphertext, looking so much like plaintext, is null and void and used to conceal the real message with a subterfuge text of its own. It may be a letter, syllable word, sentence or even a paragraph. It is the cryptanalyst’s job to find what part of the text is used for the concealed message.

If only the second word in each sentence of the following order is read, a quite different meaning is given than might be expected:


Like and distaste for the null cipher runs the gamut from high praise to ridicule. It is heralded by its supporters to belong to a concealment cipher group wishing to negate the thought of a cipher, believing the only unsolvable cipher is one that no one knows exists. Protestors of this cipher relegate it to the realm of a puzzle or riddle without principal or class.

A null cipher may declare null and void any part of its ciphertext. It may choose to exclude letters, words, sentences or entire paragraphs of its concealment text. Null variables are limited only by the creative genius of the constructor.

Consider the creative genius of one World War II serviceman attempting to evade military censors and communicate his location of Tunis, the capitol of Tunisia, to his parents during the war. Prior to his departure from home, he had arranged to spell out the name of his location by changing his father’s middle initial on his envelope. For the first letter he used a fake middle initial T, on the second, U, the third, N, and so forth. However, he neglected to date the letters and when they arrived out of order; his frantic parents scoured their atlas for NUTSI.

Here are more examples of concealed messages covered by seemingly innocent text.

Null Concealment

John Jones can always be found
hard at work at his computer without
wasting time talking. Mr. Jones never
thinks twice about helping all and he
finishes jobs on time. John takes many
efforts to do the job and skips coffee
breaks . He has absolutely not a bit of
vanity despite his work and profound
knowledge in his field. John can be
classed as A-1, the type which can't be
dispensed with. I recommend John be
promoted at once. My proposal will be
cut as soon as possible.

Consider the real message if the receiver is instructed to read every other line. A null is born by sentence elimination and one without the key is totally misinformed

A Rib Tickler Concealment Cipher

A humorous bit of dialogue making the internet tour a short time ago went like this:

He:  At last, I can hardly wait!
She: Do you want me to leave?
He:  NO! Don’t even think about it.
She: Do you love me?
He:  Of course! Always have and always will!
She: Have you ever cheated on me?
He:  NO! Why are you even asking?
She: Will you kiss me?
He:  Every chance I get!
She: Will you hit me?
He:  Never! Are you crazy?
She: Can I trust you?
He:  Yes.
She: Darling!

A contradictory sentiment is revealed when the message is read from bottom to top.

Creative Genius

In additional to what the Null Cipher has to offer as a concealment cipher is its infinite number of variable techniques, an invitation to our individual creativity.

Letters, words, syllables, lines, sentences, nouns, verbs, adjectives, adverbs, vowels, consonants, letter shapes, punctuation marks and counting patterns are only a few of the variables that can be used in the Null construction. The number of variables is limited only by our creativity.

All of these variables cast the Null in a non-user friendly computer analytical mode, allowing the cryptanalyst to open up that vast warehouse of personal ingenuity each and every time that a Null construction presents itself.

Null Construction

 There is an infinite amount of ways to construct a null. Here are just a few ways a null’s ciphertext can be keyed to disguise its plaintext:

  • Every other word
  • Every other letter
  • First letter of every word
  • Last letter of each word
  • 2nd, 3rd 4th letter each word

QUINCE – ND 1994 Cm: Having problems with a Null? Making a vertical listing of the ciphertext words on squared paper helps immensely. Makes threading through” much  easier, and you can keep track of the numbers (possible patterns) down the side. Actually,  this is also the way to construct: write the letters of the plaintext message in a list on squared paper, then surround the desired letters with others to make words, adjusting those words as necessary to create and maintain a pattern.

  • Every 2nd 3 4, etc. letter of complete ciphertext
  • (Periodic Null described at the end of this chapter.
  • Letter following each vowel

Each null below has been constructed using one of the above methods. See if you can determine the real plaintext message from its ciphertext.

Null Ciphers

N-1. Patio furniture may stain ornately sculptured tiled mall.
N-2. Leave early route, hue truly entitles rd.
N-3. Feds see pirate bunch go blow safe via borings by deli layout. FBI apprehends.
N-4. Aware, I tie a fare in teen ad.

We have related that the null cipher is one in which only some portion of the text is read as part of the secret message. The bulk of the text is null and void and is used to conceal the real message with a subterfuge text of its own. It is the cryptanalyst’s job to find what part of the text is used for the concealed message. One method that cryptanalysts use to make such an examination of the letters that make up the actual message is to construct a vertical listing of all ciphertext words to see if a message can be read in columnar order. Null messages, below, seemingly professing sadness of Holiday commercialism and one describing a winter scene will succumb to this technique.

N-5. Holiday Null. ‘Tis the season.                                             LIONEL

Once upon a time there was a glorious holiday environment present within schoolhouses amid most lands, trusting valued beliefs. Lucid thinking repeals behavior steeped in derision.

Dramatic confirmation today is a most overwhelming consensual endorsement of original catechists, in avid binge of gift proliferation for much Christmas viewing of tidings amid nations.

N-6. Null. Winter Scene.  LIONEL




LIONEL – MA 1995 Cm: QUINCE’s Notes on the Null offered sage advice on the making of a vertical listing of the Ciphertext words to thread through the chaff and extract the wheat from the linguistic prose of the null. A reverse vertical listing of the ciphertext words in a null would lead to the decipherment of nulls such as APEX DX’s challenging Confucius quotation in The ND94 Cm. APEX DX’s “antepenult” encipherment is easily read, as a reverse vertical listing of the Ciphertext reveals the cipher position to be the third from the last letter of each word.

Our JA 2008 Cm presented a Null that did not succumb to QUINCE’s “Notes on the Null described above:

E-5. Self-violating grammar rule #1.        (…ten…)        THE RAT




When QUINCE’s approach yields no logical plaintext, examine the crib letter spacing in the overall ciphertext message.

The JA08, E-5 Null crib (…ten…) reflects only one repetitive spacing of crib letters, “7,” in its ciphertext, between ciphertext words, THINK A REAL LEARNED, which allows it to be examined as a Period Seven Null. Follow the horizontal posting of the ciphertext over seven vertical columns.

Period Seven Null

       1  2  3  4  5  6  7
       R  U  L  E  D  O  N
       O  T  U  S  E  N  O
       W  O  R  D  S  I  F
       T  H  E  Y  W  E  R
       E  N  T  S  O  H  A
       R  R  O  W  I  N  G
       I  F  A  G  R  A  M
       M  A  R  E  X  P  E
       R  T  S  A  Y  S  N
       O  T  H  E  N  I  T
       P  R  O  B  L  Y  S
       H  O  U  L  D  B  E
       A  B  A  N  D  O  N
       E  D  Y  O  U  D  T
       H  I  N  K  A  R  E
       A  L  L  E  A  R  N
       E  D  L  E  X  I  C
       O  N  M  A  Y  B  E
       O  K  A  Y  I  T  S
       N  O  T.

Column seven is the charm. A Period Seven Null. Who would have ever thought it?

A comprehensive list of null variables appears in Appendix V.