Thursday, August 25, 2016

Z13: My name is... WANTOKNOWTHEZodiac

I propose that the encryption of Z13 [1] consists of 180 degree image rotation with subsequent transposition.

I start by noting that the inverted T in position 4 right-to-left gives a clue to rotate the image 180 degrees, whereby the inverted T and the 2 M's are vertically inverted and become T and 2 W's and the string starts with WANT. This is clearly a strong clue that this is the way to solve the cipher.

Of course, by doing this the letters E and K have become mirrored, but since their mirroring does not make them resemble any other letter of the latin alphabet, it makes sense to keep seeing them as E and K. The case of the 2 vertically inverted A's is different, and will provide the basis for the only step in my solution that could be viewed as an arbitrary liberty (*). For now, I will keep seeing them as A.

Writing the Zodiac sign as Z, the string resulting from rotating the image 180 degrees is:

W A N T 8 W 8 K 8 Z N E A

As the symbol that I wrote as 8 is an H within an O, a logical straightforward substitution is to replace the outer instances by O and the inner instance by H:

W A N T O W H K O Z N E A

The subsequent transposition consists of the following steps:

1. Shift left (substring, positions): (right N, 2), (KNO, 2).

W A N T O K N O W H Z E A

2. Shift right (substring, positions): (Z, 1), (HEZ, 1).

W A N T O K N O W A H E Z

(*) As a vertically inverted A is 2 t's joined at the base, I will replace the second A with T. (Alternatively, a purist could replace the second A with 2 T's and move one T after WANT.)

W A N T O K N O W T H E Z

So this is just a tease: "My name is... Want to know the Zodiac?"

This hypothesis was built from an idea mentioned in:

http://www.zodiackillerfacts.com/forum/viewtopic.php?f=51&t=1199

Since the Zodiac's April 20, 1970 "My name is" letter referred to the Z340 cipher in the previous November 8, 1969 letter, right before giving its own Z13 cipher, I propose that the encryption method of Z13 gives a hint about how the previous Z340 cipher was encoded, namely that Z340 used transposition and character mirroring.


[1] http://www.zodiackiller.com/MyNameIsLetter.html
or
https://en.wikisource.org/wiki/File:Zodiac-name.gif

Z408 last 18: EBEORIETEMETHHPITI = BEFOREIMEETTHEPIT.

I propose that the last 18 characters of Z408 have an additional layer of transposition, with only the last character being a meaningless filler and only one mistake in the text.

 E B E O R I E T E M E T H H P I T I
+4              +4
 B E O R E I E T M E T H E H P I T I
                 -2       -11
 B E H O R E I M E E T T H E P I T I
     x                             x
 B E F O R E I M E E T T H E P I T .


Facts supporting this hypothesis:

1. It results from a pattern of successive additional layers of difficulty:

- The whole Z408 is a substitution cipher.
- The last 18 characters have an additional layer of transposition.
- The last character is a meaningless filler.

2. Encoding an H instead of an F by mistake is very easy with the Z408 key, given that:

- one of the 2 symbols for F is a Q written as a circle crossed by a diagonal line;
- one of the 2 symbols for H is a circle crossed by a horizontal line.

The similarity between the 2 symbols in the cipher part mailed to the San Francisco Chronicle, which is the one contaning the last 18 characters, can be checked in the 5th column from right to left here:

http://zodiackiller.com/ChronicleCipher.html

3. It yields a coherent final sentence in Z408:

I WILL NOT GIVE YOU MY NAME BECAUSE YOU WILL TRY TO SLOW DOWN OR STOP MY COLLECTION OF SLAVES FOR MY AFTERLIFE BEFORE I MEET THE PIT

Additional points supporting this:

3.a. It makes perfect sense in the Zodiac's mental framework: he wants to keep collecting slaves until he dies, and he does not want the police to stop him from doing that before his time of death.

3.b. The clause "I meet the grave" is a standard, though infrequent, synonym for "my time of death". This can be easily verified by googling "until I meet the grave", "till I meet the grave" and "before I meet the grave".

3.c. "Grave" would not fit in the 17x8 cypher, being one character too long.

3.d. "Burial pit" is a standard synonym for grave.