Myszkowski Tutorial

Introduction

The Myszkowski (Msyz) cipher is a transposition cipher similar to the Incomplete Columnar (IC) cipher. Like the IC, the Mysz uses a keyword to order the plain text columns for removal as cipher text. Unlike the IC, the Msyz gathers up the columns with identical keyletters at the same time, further mixing up the plaintext.

Consider the following example

  • Msg: The early bird gets the worm.
  • Keyword: BANANA

For the IC this would produce:

B A N A N A
4 1 5 2 6 3

T H E E A R
L Y B I R D 
G E T S T H
W O R M

Taking off the columns in numerical order produces:

HYEO EISM RDH TLGW EBTR ART

Arranged in groups of five this provides:

CT: HYEOE ISMRD HTLGW EBTRA RT

Now consider the same message and key word for the Mszy. In this case, the columns with identical keyletters all receive the same sequence number:

B A N A N A
2 1 3 1 3 1

T H E E A R
L Y B I R D 
G E T S T H
W O R M

All the columns with identical sequence numbers are taken off at the the same time. This produces:

HERYIDESHOM TLGW EABRTTR

Arranged in groups of five this provides:

CT: HERYI DESHO MTLGW EABRT TR

Note that if the keyword is not a pattern word, the IC and the Mysz ciphers are identical. If you are not familiar with the Msyzkowski cipher, study this example. The cryptanalysis of this cipher type requires a good working knowledge of the transposition scheme.

Example

The example we will be working on is JF12 E-24:

E-24. Myszkowski. Wishful thinking! (nevervotedfor) OOBOO

HENAR SLORW PESGL AOARP PVEEA PEFVT FEDES EAYEA HOVOE FHIAL HVRNW
RAEVO PETTO THTEA FIANF TECOE NEDEP HERDR INUHH TRHEL EDLME EAANE
SMTAM R

Note that the CON is 116 letters long and contains the plain text “…never voted for…”.

Period Determination

The first step in decrypting the Msyz (and the IC) is to determine the period of the CON. For this, we use the information provided by “The ACA and You” which indicates that a standard Msyz is 12-15 lines deep. (Be careful when using this type of info. It is not always accurate, but it is usually a good starting point.)

If the CON were 12 lines deep the period would be:

P = (116)/12 = 9.66 ~ 10

If the CON were 15 lines deep the period would be:

P = (116)/15 = 7.73 ~ 8

This indicates that the period of the CON should be in the range of 8-10. Now lets look at the crib. For the candidate periods, this indicates that the plain text must contain the following partial columns:

 Period 8: NEVERVOT     Period 9: NEVERVOTE      Period 10: NEVERVOTED
           EDFOR                  DFOR                      FOR

Note the presence of the low frequency letter ‘V’ at the start of the crib. Examination shows that either the sequence V*F, V*O, or V*R should appear in the CON. The ‘*’ represents that the two letters may not be in contact. They however should be close to one another and any intervening letter strings must be in the crib in the correct sequence. Searching the cipher text for the occurence of the letter V provides the following locations of interest:

Position   Letter Sequence   Period
  22       VEEA              Reject. Inconsistent with the crib.
  29       VTFE              Period 8 with double column.
  43       VOEF              Period 9 with single column.
  52       VRNW              Period 10 with single column.
  59       VOPE              Period 9 with single column.

We have four possibilities with position 29 looking the most promising due to the unlikely proximity of the low frequency letters V and F. Let’s proceed with this as a starting point.

Plain Text Reconstruction

With an assumed period of 8, the columns in the plain text would have on average a length given by:

Length = (116)/8 = 14.5

We can now begin to seperate the cipher text into ‘proto-columns’ by dividing the CON up into eight groups of approximately 14.5 letters each. This can be done by breaking up the CON in groups of alternating length of 14 and 15 letters long. This provides:

PC   CT
 1   HENARSLORWPESGL
 2   AOARPPVEEAPEFV
 3   TFEDESEAYEAHOVO
 4   EFHIALHVRNWRAE
 5   VOPETTOTHTEAFIA
 6   NFTECOENEDEPHE
 7   RDRINUHHTRHELED
 8   LMEEAANESMTAMR
 

Note: These columns are not exact, but they shouldn’t be off by more than one or two letters.

Our sequence of interest, VTFE, appears at the break between proto-columns 2 and 3. This is consistent with this sequence being in a double column (we already knew this), positioned approximately in the middle of the plain text (new info). Using this as a starter around the crib we obtain:

Col  * * 2 * * * * 2
     - - - - - - - A
     - - O - - - - A
     - - R - - - - P
     - - P - - - - V
     - - E - - - - E
     - - A - - - - P
     - - E - - - - F
     N E V E R V O T
     E D F O R - - E
     - - D - - - - E
     - - S - - - - E
     - - A - - - - Y
     - - E - - - - A
     - - H - - - - O
     - - V - - - - O

Now we proceed to use what remains of the doubled columns in the crib. Note the RR in column 5 of the plain text. We search through the proto-columns looking for an ‘R*R’ sequence either in the middle of a single column, near the break of a double column or in the middle of a three column sequence. (Do you understand why this must be the case?)

Note that at the break between proto-columns 6 and 7 we have the sequence ERDR. This fits into the crib perfectly as a double column and provides:

PC   CT
 1   HENARSLORWPESGL
 2   AOARPPVEEAPEFV
 2   TFEDESEAYEAHOVO
 4   EFHIALHVRNWRAE
 5   VOPETTOTHTEAFIA
 6   NFTECOENEDEPHE
 6   RDRINUHHTRHELED
 8   LMEEAANESMTAMR
Col  * 6 2 * 6 * * 2
     - - - - N - - A
     - F O - T - - A
     - E R - C - - P
     - O P - E - - V
     - N E - E - - E
     - D A - E - - P
     - P E - H - - F
     N E V E R V O T
     E D F O R - - E
     - I D - N - - E
     - U S - H - - E
     - H A - T - - Y
     - R E - H - - A
     - E H - L - - O
     - E V - D - - O

Note that we now know that proto-columns 1 and 8 must be single columns in the plain text due to there position in the cipher text. Further note that the partial text appears consistent with ordinary English. (Always a good sign!)

The only remaining candidate for a multiple column sequence are proto-columns 3 and 4. Notice that the sequence EVO appears at the column break and fits into the crib well. Making this substitution provides:

PC   CT
 1   HENARSLORWPESGL
 2   AOARPPVEEAPEFV
 2   TFEDESEAYEAHOVO
 4   EFHIALHVRNWRAE
 4   VOPETTOTHTEAFIA
 6   NFTECOENEDEPHE
 6   RDRINUHHTRHELED
 8   LMEEAANESMTAMR
Col  * 6 2 4 6 4 * 2
     - - - - N E - A
     - F O F T H - A
     - E R I C A - P
     - O P L E H - V
     - N E V E R - E
     - D A N E W - P
     - P E R H A - F
     N E V E R V O T
     E D F O R P - E
     - I D E N T - E
     - U S T H O - E
     - H A T T H - Y
     - R E T H E - A
     - E H A L F - O
     - E V I D A - O

The partial English text (e.g., never) indicates we are on the correct track. A quick search near the mid point of proto-column 8 reveals the sequence NE, indicating that it is corresponds to the first column of our plain text reconstruction. By default, proto-column 1 must fall into position seven. This provides:

PC   CT
 1   HENARSLORWPESGL
 2   AOARPPVEEAPEFV
 2   TFEDESEAYEAHOVO
 4   EFHIALHVRNWRAE
 4   VOPETTOTHTEAFIA
 6   NFTECOENEDEPHE
 6   RDRINUHHTRHELED
 8   LMEEAANESMTAMR
Col  8 6 2 4 6 4 1 2
     - - - - N E H A
     L F O F T H E A
     M E R I C A N P
     E O P L E H A V
     E N E V E R R E
     A D A N E W S P
     A P E R H A L F
     N E V E R V O T
     E D F O R P R E
     S I D E N T W E
     M U S T H O P E
     T H A T T H E Y
     A R E T H E S A
     M E H A L F G O
     R E V I D A L O

A quick review of the plain text shows that the last letter assigned to proto-column 2 should have been the initial letter of proto-column 4. Moving this one letter then provides the plain text:

One half of the American people… . Gore Vidal

Starting from the beginning of the plain text and wrapping around to the end we discover that the sequence of the letters in the keyword must be:

   4 6 4 1 2 8 6 2

Based on this, the key has a pattern of ABACDEBD and a sequence of 34312542. My pattern word database indicates that the only possible keyword is DIDACTIC.