You’re the second person to mention that in the last few days. Here’s Weir’s post on the halloween card ‘Envelope’ thread.

Thanks Trav for pointing this out! I haven’t been keeping up with many threads lately. An interesting coincidence that we end up discussing the null cipher type coming from 2 different angles.

I read everything. Just glad to be of use. I did note that it was a different approach but thought it was curious that ‘null’ cipher came up in both instances.

I’m skeptical about this approach

You and me both , but I still find it interesting enough to share it.

3) There are 41 unique symbols, which greatly increases the difficulty of solving it…

Good job in creating this so rapidly! Not too surprising that ZKD would have a hard time decrypting this given the length and number of symbols (assuming, of course, there is something intelligible to be extracted in that cipher subset).

I find it interesting that the number of prime positions in 340 is a multiple of 17… Anyway, I’ll keep playing with this null cipher idea for a bit to see if something pops up.

I find it interesting that the number of prime positions in 340 is a multiple of 17…

That made me very curious so I did a little test.

A grid with R rows and C columns has R*C symbols in it. Let P = number of symbols that fall on prime positions.

How many grids have P that is a multiple of C? I tested R from 2 to 100, and C from 2 to 100. Here are the results:

http://zodiackillerciphers.com/grid-primes-count.txt

459 out of the 9801 grids have P that is a multiple of C. That’s about 5% of them. So, I suppose it’s not too uncommon.

A question Doranchak please, if you would……if you take this whole idea and were to apply it across all of Z’s communications and if that demonstrated a partiular pattern, would it be possible (statistically/scientifically) to prove that the pattern was there by design or chance?
Thanks.

That’s about 5% of them. So, I suppose it’s not too uncommon.

Thanks for calculating that. We’ll just pile this on top of the coincidence heap I suppose.

BTW, we assume that the zodiac knew that 1 wasn’t a prime number …

A question Doranchak please, if you would……if you take this whole idea and were to apply it across all of Z’s communications and if that demonstrated a partiular pattern, would it be possible (statistically/scientifically) to prove that the pattern was there by design or chance?
Thanks.

It really depends on the pattern I suppose. Some patterns are easy to show happen by chance. Other patterns, while seemingly rare, belong to a class of patterns that considered as a whole are not rare.

Other patterns are astronomically rare, such as the mapping from the 408’s cipher alphabet to plain text. It’s extremely unlikely that such a mapping accidentally revealed a "pattern" of so much legible prose.

Fascinating ideas.

So let’s chop out all the symbols that do NOT fall on prime positions. The result is this 68-character cipher:

1) Look how it divides nicely into four lines, each with 17 columns just like the "parent" cipher text.
2) The words "YOU", "WAYS", and "OF" seem to pop out.
3) There are 41 unique symbols, which greatly increases the difficulty of solving it if it’s truly a standalone substitution cipher.
4) But I tried it in zkd anyway, using this transcription:

ERp^|Ldp#.*:UGLp*
3KMzF4^kD#q;XOYdM
y6UOFRDBlJTM+Gf2c
yXUc(MGL<FW|W7YS|

and got this gibberish: PYABLESANDNOTHEANDITWERBLONGESHESTINTHEYOUSTATTHEMOISTOFTHEREALACEIL

Just looked for words, this is what i found:

PYABLESANDNOTHEANDITWERBLONGESHESTINTHEYOUSTATTHEMOISTOFTHEREALACEIL

PY ABLE S AND NO THE AND IT WE RB LONG E SHE STIN THE YOU STAT THE MO IS T OF THE REAL ACEIL

ABLE AND NO THE AND IT WE LONG SHE IN THE YOU AT THE MO IS OF THE REAL

OR this:

PYABLESANDNOTHEANDITWERBLONGESHESTINTHEYOUSTATTHEMOISTOFTHEREALACEIL

PY ABLE S AND NO THE AND IT WE RB LONG ES HE STINT HE YOU ST AT THE MOIST OF THE REAL A CEIL

ABLE AND NO THE AND IT WE LONG HE STINT HE YOU AT THE MOIST OF THE REAL A CEIL

I have no idea if this has any merit. I doubt it, but choose to post it anyway…