Zodiac Z13 Cipher Solution

Sam Fisher
2 min readFeb 19, 2022

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The solution to the Z13 Zodiac Cipher sent on April 20, 1969.

Z13 Zodiac Killer Code

I believe that the Zodiac Killer is/was Joseph Paul Franklin.

Born James Vaughn Jr = 13 characters

I am going to encrypt James Vaughn Jr into this code here.

Keep in mind that the letter was sent on April 20, 1969, which is Adolf Hitlers birthday.

Keyword: Adolf Hitler

A note before I begin. The symmetry is very important here. As you can see the code is symmetrical and the solution is as well I will explain.

If you don’t know what the Z13 looks like look up: Z13 Zodiac Killer on Google Images.

Tabula Recta:

Tabula Recta

Taking James Vaughn Jr through this produces the following cipher text:

ADAPXCINRLEAU

Notice that the J’s become A’s.

The D is shifted + 1 = E

The C is shifted + 8 = K

We now have 18 and 18 on both sides to produce the following:

AEAPXKIMNAM

Notice the left side is missing an N

The NA on the right side is the key to the left side and vice versa:

In the final code the second A becomes an N. After looking at this for a bit I realized a symmetrical solution would be the two inside “A”s are the key to the other ones.

So for example in the ending NAM

N = A

Apply that to the left side and you get the AEN

In the AEN the key says E = N

So in the original cipher of: ADAPXCINRLEAU

the A and E become N’s because they are each the key to the other side.

It is symmetrical with the partial key built into the cipher.

The Aries symbol is because James Vaughn Jr is born an Aries.

The triple 8’s in the middle not sure, but the Zodiac symbol is in the place of where the only “E” appears in his name which is curious.

So here you have a path and my solution to the Z13.

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