Since I've Got The Time

Genetic search algorithms and hill-climbers are all very serious business, so I thought I'd try out a couple of educated guesses on the transposition key for the D'Agapeyeff Cipher for fun.   Why?  Why not?  I've definitely got the time.  Sure it's a 1 : 87 billion guess, but it's EDUCATED! :)

I started with a few of my usual assumptions:

1.  Strip out the odd digits from the ciphertext (all the 5, 6, 7, 8, 9, and 0 digits)
2.  Write the ciphertext vertically into 14 columns (14x14 grid)
3.  Assume that "04" near the middle of the cipher text marks the last character in the cryptogram

That leaves us looking for a 14 character transposition key, where the last column of the original matrix is what I like to call C7 (Column 7 after transposition).

What do we know about Alexander D'Agapeyeff?  We know he was a cartographer, born in Russia, and lived (and died) in England.  We also know that he showed us an example of substitution + fractionated transposition in his Codes and Ciphers book:

A cartographer living in the UK you say?  I believe it.  Mr. D'Agapeyeff used MANCHEST(E)R as the keyword in his example.  As you can see, he removed the 2nd instance of "E" to give a resulting 9 columns for the transposition key width.

Let's assume for a moment that he's playing by the same rules with his challenge cipher.

We're looking for a key phrase with 14 unique letters.  Not exactly a simple task.

NOT EXACTLY A SIMPLE TASK.  There are 21 characters in that sentence, but only 14 unique.  But let's revisit the mind of a cartographer.  A man who made maps for a living.  No doubt his mind is littered with names of places.  Towns, villages, cities, countries, etc.

Let's also revisit one of the first assumptions:

"That leaves us looking for a 14 character transposition key, where the last column of the original matrix is what I like to call C7 (Column 7 after transposition)."

 Okay, so we need a key phrase where the last unique character is somewhere near the middle of the alphabet.  Why is that?

Remember when a key is finished being transposed, essentially what you have is:

MANCHESTR to ACEHMNRST

If we "know" (and I use that term loosely, remember this is just for fun) the last letter of the keyword alphabetizes to the 7th position there needs to be 6 letters preceding it and 7 following it in the alphabet.

ABCDEF     GHIJKLMNOPQRS     TUVWXYZ

We can rule out A-F being the last unique letter in the key phrase, as well as T-Z.  That leaves us with G-S as the possibilities.  But let's be realistic.  I highly doubt all of ABCDEF or TUVWXYZ are all used in the keyphrase.  We are likely looking for a key phrase where the last unique letter is IJKLMNOPQ.

So back to D'Agapeyeff's keyword of choice in his book.  MANCHEST(E)R.

MANCHESTER UNITED KINGDOM.  15 unique characters.  Probably not it (I tried)

But hey, there are a ton of cities in the UK for a map maker to draw from, and there are 8 unique letters just in "UNITED K(IN)G(D)OM".  Added bonus that M and O are the last unique letters provided that they both don't show up in the city name you choose.  Take for instance Liverpool.

LIVERPOOL, UNITED KINGDOM

LIVERPO(OL)UN(I)T(E)DK(IN)G(DO)M.  14 unique characters.  When alphabetized:

DEGIKLMNOPRTUV.  M is the last unique character and falls into the 7th spot when reordered for transposition.  Beautiful.  Cipher Solved!  Re-arrange the columns, pair up the digits to form the 2 digit numbers from the polybius square used for substitution and plug into my mono-alphabetic substitution solver
, and . . . . nope, garbage.  Coventry fit the bill as well, but no dice there either.

But hey, it wasn't hard to try with a spreadsheet setup to do all the leg work.  Realistically I checked the phi-test value (380 something) and it told me it wasn't English.