Hi,
I’ve searched the forum for threads about the polybius square and found some posts in the huge „Homophonic Substitution“ thread. In those posts the polybius square was used in combination with bifid. Maybe I have overlooked something but I have not found a topic where the polybius cipher was considered in its basic form in combination with homophonic substitution. If someone had posted the following idea before, I may delete my new thread.
Allright then, let’s have a look at a polybius square in combination with a homophonic substitution. To keep things simple I don’t use a keyword to build the square:
As you can see, the polybius square results in a monoalphabetic substitution. Now consider the numbers „1“ to „5“ as the plaintext. You can apply a homophonic substitution and get the results found in the image above.
Now let’s have a look at another variation:
This time two different keys are used. One for the numbers in rows and one for the numbers in columns. The keys consists of the same symbols but in a different order. To encode a polybius message in this way gives you great freedom when assembling the final cipher. You can make parts of the ciphertext look cyclic or like a pattern. You can even put fake bigrams in the cipher to fool everyone. You can imagine how easy it would be to create even such patterns like the pivots.
If Zodiac had used such a system then two things gives me headache:
– The plaintext consists only of 170 letters which is much harder to decipher
– I have no idea how to solve such a cipher
What do you think?
Merry Christmas!
Edit: Fixed a "bug" in my sample images
Merry christmass.
If Zodiac had used such a system then two things gives me headache:
– The plaintext consists only of 170 letters which is much harder to decipher
– I have no idea how to solve such a cipherWhat do you think?
It could be useful to create a couple of these ciphers to look for statistics that stand out. To solve it, convert a language corpus to polybius with suspected key and train ngrams on that.
Largo,
What you propose is a plaintext encoded with polybius:
34 33 24 45 33 15 43 24 53 44 15 15 33 44 52 34 44 23 34 45 43 11 33 14 11 33 14 21 24 21 44 15 15 33 44 42 45 32 35 11 33 33 34 45 33 13 15 14 23 24 43 13 11 33 14 24 14 11 13 54 21 34 42 35 42 15 43 24 14 15 33 44 34 21 44 23 15 45 33 24 44 15 14 43 44 11 44 15 43 11 44 44 42 45 32 35 44 34 52 15 42 24 33 33 15 52 54 34 42 25 13 24 44 54 24 33 44 23 15 43 35 15 15 13 23 44 42 45 32 35 14 42 15 52 11 44 44 15 33 44 24 34 33 44 34 14 34 32 15 43 44 24 13 24 43 43 45 15 43 43 45 13 23 11 43 24 31 31 15 22 11 31 24 32 32 24 22 42 11 44 24 34 33 34 21 21 43 23 34 42 24 33 22 34 21 11 32 15 42 24 13 11 33 24 34 12 43 44 23 15 45 43 33 11 44 24 34 33 11 31 14 15 12 44 11 33 14 24 43 31 11 32 24 13 44 15 42 42 34 42 24 43 32 52 23 24 13 23 11 31 31 42 15 32 11 24 33 15 14 31 11 42 22 15 44 23 15 32 15 43 14 45 42 24 33 22 44 23 15 13 11 32 35 11 24 22 33 23 15 11 31 43 34 11 33 33 34 45 33 13 15 14 23 24 43 13 11 32 35 11 24 22 33 43 31 34 22 11 33 32 11 25 15 11 32 15 42 24 13 11 22 42 15 11 44 11 22 11 24 33
And then remove the spaces and treat each single digit as a symbol and encode it with homophonic substitution:
1 62 7 15 3 2 41 4 18 22 5 6 44 26 49 45 6 31 20 46 12 9 14 23 32 35 28 41 42 53 37 44 45 46 55 38 39 48 41 60 48 52 16 19 59 1 21 51 14 16 1 7 19 17 56 21 3 20 25 24 27 28 36 42 43 60 15 35 30 33 41 29 44 61 37 34 38 4 47 50 39 52 59 1 7 45 46 6 15 18 16 22 19 9 21 48 40 26 49 45 46 31 24 32 14 16 35 38 19 48 53 51 21 62 24 36 14 37 23 2 55 54 38 8 11 56 39 42 27 3 57 60 27 52 10 28 58 17 63 61 59 1 51 62 38 2 3 58 8 11 10 39 63 61 17 61 22 26 49 20 27 28 5 42 12 30 28 15 30 33 63 5 41 48 12 42 28 18 14 16 41 44 45 46 48 3 51 60 1 10 7 6 62 46 15 48 61 13 19 4 51 25 53 62 18 38 39 7 21 6 9 55 23 46 15 48 51 56 3 42 43 18 10 62 2 8 60 11 13 2 31 39 8 11 25 1 21 61 17 7 15 4 54 6 57 9 5 18 29 52 20 27 11 34 44 23 59 40 1 42 12 45 46 49 14 60 61 10 16 19 17 20 27 28 21 4 7 15 45 46 13 48 18 45 22 7 46 48 35 51 24 62 37 2 59 25 58 6 62 1 2 8 13 11 63 37 25 17 20 38 27 39 28 42 5 4 30 52 20 59 33 6 12 1 29 7 14 16 41 15 34 44 18 19 22 21 24 6 40 49 36 36 37 43 53 45 38 55 39 56 53 46 55 56 48 3 47 50 51 48 10 51 1 62 7 15 38 2 25 54 29 24 8 39 34 52 39 11 17 34 40 11 52 59 49 53 37 17 55 36 47 50 26 56 54 9 20 13 25 27 57 39 58 63 52 59 29 28 52 33 5 34 41 32 28 51 40 18 12 23 62 42 2 38 39 52 50 54 8 11 49 17 59 20 1 7 57 58 15 63 5 27 12 60 21 53 28 30 24 36 18 22 47 33 55 41 30 26 38 58 63 5 39 40 49 33 12 52 41 44 58 61 45 53 46 55 59 48 51 56 29 62 2 22 7 34 4 40 49 35 53 8 63 37 55 38 43 47 39 50 31 54 11 56 57 60 32 3 58 63 53 17 35 37 5 61 12 20 38 14 54 57 27 49 53 55 54 4 28 27 56 39 57 6 52 3 58 9 33 59 12 41 44 23 45 40 49 2 37 38 53 34 27 28 40 39 14 23 16 31 36 43 15 49 18 42 47 50 34 30 40 49 22 26 53 31 54 42 57 58 38 63 33 39 15 41 5 43 18 22 15 18 22 48 20 4 26 31 47 32 50 6 24 62 55 35 56 2 8 37 21 38 24 36 39 3 52 9 54 57 10 11 13 25 59 1 17 31 32 58 35 41 29 34 54 43 37 38 39 40 47 50 49 23 5 42 21 24 52 53 57 9 44 55 56 45 58 59 63 5 3 10 46 13 12 23 14 43 48 51 47 50 40 49 54 57 53 62 1 7
So, if this is the case in the 340 then we would indeed have only 170 original plaintext letters:
491_TY('&><IN6E]I
K;VRX=/"CJ(HZ?N]V
.+#5(*5GO0$43B=O4
10M3T;:^QJ!H8*_C
L2(,ND?-+'F@#G$41
]VI_&O>0X35%6E]VK
^"=OC+05ZB39^!=?/
Y.[+SU#HQTW*QG7J
)MPD$4B9+YT)SU7#P
DMD>6E;QJ<HRLJ_L2
P<(5RHJ&=O(N]V5TB
*471I9V_5DA0'B:Z9
&+#13IX./V_5BTH8
&79YS*UAYK#SU:43D
M1_'[IWX<&,G;QU-N
/$%4HR]VE=*D7O0M;
QJ3'1_]VA5&]>1V5C
B^9?Y$:)I94YSAUP?
:M;+Q#JH<'LG;$2IR
4,1=O(_-N&0>3^I%E
I’m not sure how to solve it, I posted an idea in my previous post but it seems unpractical. Merging by pairs results in 278 unique symbols for a 340 ciphertext so that is out of the question.
What I find interesting is that if such a scheme is actual, then probably only 5 to about 10 symbols would have to be homophonically substituted. So, if Zodiac then cycled like in the 408 we would come to conclusion that there were only 5 to 10 original symbols to begin with and we could strongly suspect such a scheme. Thus, perhaps Zodiac in all his wisdom foresaw this and messed up the cycles.
Could we come up with a test that estimates the number of symbols before encoding?
