(crossposted from reddit)

The 13-character cipher from Zodiac has some repeating symbols, seen here:

http://zodiackillerciphers.com/images/z … tterns.jpg

If we assume the cipher is a substitution cipher, then any time a symbol repeats, it stands for the same underlying plaintext letter.

For example, in a solution, the 1st and 12th letters have to be the same. The 3rd and 11th letters have to be the same. The 8th and 13th letters have to be the same. And the 5th, 7th, and 9th letters have to be the same.

I got curious again about what solutions could fit, and analyzed many gigabytes of text from Project Gutenberg ( https://www.gutenberg.org ). Here are some interesting hits:

CHIEF OF AFRICA
UNCLE PETER CUT
OF HAIR IT IS HOT
OF THESE NEWTON
AT ME O SON OF MAN
A WIDE VENETIAN
A RIPE VENETIAN

If you allow different symbols to decode to the same letter, then the cipher is considered "homophonic", and these are some hits:

AVIS, A CANADIAN
INDIA. WAS, AND IS.
I SAW ALAN AGAIN
I WAS A MAN AGAIN
I HAD A MAN AGAIN
NEAR A WAY AS ANY
CLAUS ASKS JACK
GUEST AT OTSEGO
ONE HAS A NAME ON
ONE HAD AN AXE ON
AS IF A CANADIAN
OH NO IT IT IS NOT
IS THAT AS ART IS

The letter says "My name is _________. I am mildly cerous as to…" These solutions end with "AND" which helps them run into the next sentence in the letter:

NEARER EDEN AND
NIAGARA DAY AND

I don’t think any of these are the real solution. Would we even know it if we found it? We don’t even know yet if the unsolved ciphers are "real" ciphers. And once you start changing the rules of how Z13 works, you can generate so many more potential solutions! http://zodiackillerciphers.com/wiki/ind … _Solutions