Aristocrat Substitution Cipher

We are ready to begin having fun with classic cryptography. Let us begin to discuss the tools and techniques that allow the cryptanalyst (that’s you) to find the ciphertext message without possessing the actual key.

The classical substitution type cipher, which retains word breaks and is seen most often in your local daily newspaper, is called the Aristocrat cipher.

In real life cryptography we have some knowledge and probably a lot of ciphertext to analyze. Newspapers and magazines such as our own Cm have space restrictions which limit the amount of ciphertext they can print. In place of large amounts of text which aid solving, subject titles and tips (also known as cribs) are provided. Tips are often given in Caesar format that require determining the number of letter shifts (see Chapter One) to identify the plaintext word to be placed in the message.

Analysis of the Aristocrat cipher begins by checking the title for thoughts of words that might appear in the plaintext. If a tip appears, look for its proper spot in the cipher. Look for common short words (in, it, is, of, no, on, and, the). ‘The” often starts of a sentence. One letter words most always are “a” or “I.”’. (Rare exceptions are “O,” “X” marks the spot.)

Letter frequency counts may lead us to the most often used letter “e”. Pattern words are those words having repeat letters. We think of the common pattern word “that” in terms of 1-2-3-1, meaning the first and last letter of the word are the same.

Try these deciphering tools on the following cipher example and check your answer on our Solutions Pages at the end of this Tutorial.. Keep in mind that once a cipher text letter is used for a given plaintext letter, it must always be used for the same letter.

A-Example. Cryptography lesson.   (AFPDRFPBA – Caesared tip.)

     DNO  KPIMDAUPQMNOP  LC  QXGQIC

     KNOKWLZU TAP  CYQXX  GAPSC  AP

     CLZUXO  XODDOP  GAPSC  DNQD  MPAFLSO

     Q  UAAS  OZDPI  MALZD  LZDA  DNO

     SLCUELCOS  YOCCQUO.

A-1. Solvers delight.   (ABIFDEQBA – Caesared tip.)

TROWFGT  HGF  JFOCLEUFJ  XEFQ  UEFZ  JCTBRWFG  UEF  GFDFHUFJ VTF RK

UEF  PRTU  KGFSVFQU  WRXFO  CQ H  BCDEFG .

A-2. What is the crib of A-1?

A-3. What is the most frequent letter in A-1?

A-4 . How many pattern words are in A-1?

Are you having fun yet?  We are going to spend many columns talking about the Aristocrat cipher, the cipher that your daily newspaper holds synonymous with ‘cryptogram’. Let’s continue our discussion with some of the many tools that are helpful in solving Aristocrats as well as many other cipher types.

Titles and tips. Do not overlook cipher titles as good leads to plaintext words. Each plaintext word correctly placed provides valuable letters to other words in the cipher.
Caesar Cipher tips. Remember your alphabet training to convert any ciphertext
tip to plaintext. Placing the tip in a message generates leads
to many other words in the plaintext.
Frequency count.. The first step in solving by most cryptanalysts is a simple tally of how often each ciphertext letter appears in the message. This is called a frequency count and is used to compare each ciphertext letter of appearance with that of the normal frequency of letters in the English language. Such a comparison allows us an educated guess of what a ciphertext letter may be.The “ACA and You Handbook” provides the following values:

ENGLISH LANGUAGE FREQUENCY TABLE

    (Percent occurrence)
 e  t ao nir sh ld cupf mwy bgy
13  9  8  7  6   4  3    2   1

kqxjz - less than one percent

Senorita

Letter frequency counts are a most effective tool in cipher solving.  Senorita is the key to frequent letter repetition. It contains most all of the frequently used letters. Align the most and least used letters with the frequencies of letters appearing in the above table. It will be a significant aid in providing a breakthrough to your solving process.

Short words – Look for these short words in a cipher: “a” and “I” (the only single letter words), an, in, is, it, on, of, the (often starts a sentence and often appears more than once in a cipher), was, why you .

Pattern words -These are words with repeating letters . Look for these common pattern words: All, off, too, see, good, poor, that, there, where, these, little, people.

Cross Checking

 The phenomenon of cross checking pattern words in an Aristocrat cipher, also referred to as cross-correlation, cross-matching, cross-reduction and cross-referencing, is a valuable tool in uncovering much of an Aristocrat’s plaintext. The following examples will demonstrate its usefulness.

JF 11. A-11. The marrying kind.              DYETI

A check of our pattern word list for the plaintext (pt) equivalent of ciphertext (CT) IOSHUPZKQO (Pattern 1234567892) found in this cipher reveals the words “admonished, centigrade, despicable, neutralize personable and persiflage” as being represented by the same pattern.

CT letters ISOPOSH (pattern 1234325) would reveal the words “brewery, granary, prefers, revived, synonym and utility” as plaintext pattern fits.

A simple check of the like ciphertext letters in each ciphertext word (ISOPH) will lead you to the correct pattern plaintext word for each, “persiflage and prefers” and generate more leads to the cipher’s plaintext.

See our MJ10 Tyro Grams column for a discussion of pattern word lists. The pattern word “people” would be defined as a word having a pattern of “123142.” The “1’s and 2’s” indicate the repeating letter position of the letters “p and e.”

JF 11. A-13. Isn’t that special?             ANGO-KA

Pattern ciphertext word DUVWFXVW yields plaintext pattern words “aluminum, bungling, distrust, hastiest and sometime” as potential word solutions while the ciphertext pattern word MFUDHFZX yields the words “absorbed, dilution, fidelity, feathers and mahogany” as possibilities. A simple check of like letters in each ciphertext word will identify the proper fitting plaintext letters and lead to more plaintext words in the cipher.

Here is another cross check which will lead to much more plaintext recovery.

MA 11. A-14. Music.                                  DUMPSTER

 Cross-check PNWJRBZKNZM with pattern words, “dipsomaniac, discounting, dismounting, miscounting and realignment” versus APRZHRAWJ, pattern words, “coatracks, convinced, principal, principle and traumatic” for the proper plaintext fit of each. See how many additional words of plaintext become identifiable with the letters you have distinguished.

Pattern Word List Reference

Google, Design215 Word Pattern Finder – Find Words with Similar Patterns for word lists that will reveal words by pattern numbers.

Abridged paperback list of pattern words such as included in Norma Gleason’s book of Cryptograms and Spygrams provide the most often used words in the English language and is much easier to peruse than those long lists of all inclusive words in the English language that may be found on the Internet.

The non-pattern word list is a great aid in performing word cross matching. This technique is served by comparing the like letter positions in ciphertext words and finding the word fit on the non-pattern word list which will provide you with two plaintext words to assist you in the solving process.

Crib Dragging

 Crib dragging is a stimulating manual exercise and great time filler for those long waits at the doctor’s office or waits on significant others at shopping malls.  A given crib needs to be simply placed in each ciphertext position to observe those plaintext letters that are generated as a result of each position placement.

Miscellany

Each ciphertext letter may stand for only one other plaintext letter. Each plaintext letter must be replaced by a ciphertext letter not equal to itself. (ACA simple substitution ciphers do not allow “self-encryption,” (the act of allowing a letter to stand for itself.) An asterisk indicates the use of a proper noun which may, or may not, be part of the English dictionary.

Let’s put these tools to use in solving the cipher and answering the questions below.

A-5. Solving tools.   (CXJFIFXO)       LIONEL

EOP  *YMUUPP  *YCQBPQ  LCZFAB  MR  S

WCCU  HSJ  EC  ZPSQB  SBU  TPLCAP

VSAMZMSQ  HMEO  ASBJ  CV  EOP  ZMEEZP

ECCZR  EOSE  SQP  OPZNVFZ  MB  RCZGMBW

*SQMRECLQSER.

* Proper noun or name.

A-6. What plaintext letter appears most?

A-7. What plaintext letter appears least?

A-8. How does the frequency of the most and least plaintext letters in this cipher compare to their frequency in the English language?

Let’s apply many of the principles of cryptanalysis which we have been discussing to a simple substitution Aristocrat Cipher that appear below.

A-9. Corn harvest.   [105]   (for)   LIONEL

PDA YKNJ BWNIANO EJ PDA

YAJPNWH WJZ JKNPDANJ LWNPO

KB PDA *QJEPAZ *OPWPAO HKKG

BKN YKNJ OPWHGO PK XA GJAA

DECD XU PDA BKQNPD KB *FQHU.

 Solving Principles

Title note: A harvester of corn may appear in the plaintext, a farmer or comedian, perhaps?

Look for the best fit position of the three letter crib, “for.” It would seem unlikely to begin the cipher.

We note the ciphertext letters, PDA, at the start of our cipher, repeating three more times in this cipher; a good candidate for the most used three letter word in our English language

Nine ciphertext letters appear at least five times, all candidates for our senorita plaintext letters.

There are six, two letter ciphertext words that may fit frequently used plaintext letters “in, is, it, on, of, to, be.”

Many proper nouns (*) with repeat letters appear in pattern word lists. Look for *OPWPAO.

Digraphs and Trigraphs

Let’s discuss some additional principles that prove helpful in converting ciphertext (CT) to plaintext (pt). Webster defines digraph as “two letters portraying a single sound” and trigraph as “three letters depicting a single sound.” These two and three letter groupings lend an aid to the solving process. Recognizing the most frequently used digraphs and trigraphs allows us to consider additional adjacent plaintext letters.

Awareness that “th” is the most frequently used digraph, that “er” and “re” the most frequently reversed digraphs and that “the, ing, and” are the most often used trigraphs is a most helpful aid to plaintext recovery.

 Most Frequent Digraphs and Trigraphs

TH ER RE IN AN HE AR EN TI TE AT ON ED ND HA

THE ING AND THA ION ENT FOR TIO ERE HER ATE VER TER

Solving Lucidity

One’s solving logistics, plaintext insight and ease of continuity will be helped by the use of UPPER CASE letters for ciphertext, lower case letters for plaintext, letter certainties in red.

A-10. Aristocrat.  Holiday Fun.  K1   (seem)               LIONEL

IZDL  RSD  LYZDL  TUC  RSLIMXS  RSD  NIIC,  TUC  WRLTYXSR  RSLIMXS  RSD

ATLUPTLC XTRD.  ND  WDDH  RI  XI  DORLDHDGP  WGIN, YR  YW  WI  STLC  RI

NTYR.  IZDL  RSD  LYZDL  TUC  RSLIMXS  RSD  NIIC,  UIN  XLTUCHIRSDL 'W

BTJ  Y  WJP!  SMLLTS  EIL  RSD  EMU!  YW  RSD  JMCCYUX  CIUD? SMLLTS  EIL

RSD  JMHJVYU JYD.  GPCYT BSYGC

A-11.  Aristocrat.  Peace on Earth.  K2 (161)              LIONEL

*QWSXBCLNB,  *WNIEHHNW,  NIR  *HGNIMNN, QDIT  PEC  DLQT  N  KTNS.

GWTI  CWTK  QDLT, CWTK  PSXIV  VSTNC  QWTTS. N  WNFTI  CWNC  ATNQT

LNK  VSNQT, LNK  GTOO  PT  GXCWXI  DES  DGI  TLPSNQT, BWDEOR

VDDRGXOO  DQQEAK  DES  ATSBDINO  BANQT.

See Appendix I – Few Pocket Tips