(Back to zodiackillerciphers.com)

Contents:

Annotated solution to the 408 cipher, based on the Harden worksheets
- Notes
Harden Key
Differences between Harden Key and Concerned Citizen Key
Interpretation of FBI cryptanalysis of Concerned Citizen Key

Annotated solution to the 408 cipher, based on the Harden worksheets

(Sources: [1] [2] [3] [4] [5] [6]). Word divisions are marked. Annotations appear as red numbers - click on them to view more details. Colored boxes indicate cipher symbols that violate the rule that a cipher symbol can only represent a single plain text letter.

Part 1, mailed to Vallejo Times - Herald on July 31, 1969

row 1:

row 2:

C¹

row 3:

F²

S³

M⁴

R⁵

row 4:

row 5:

T⁶

A⁷

row 6:

row 7:

O²⁰

S⁸

row 8:

Part 2, mailed to San Francisco Examiner on July 31, 1969

row 9:

T⁹

row 10:

E¹⁰

row 11:

row 12:

F¹¹

row 13:

L¹²

row 14:

T¹³

row 15:

row 16:

E¹⁴

A¹⁵

Part 3, mailed to San Francisco Chronicle on July 31, 1969

row 17:

E¹⁶

row 18:

row 19:

row 20:

Y¹⁷

row 21:

W¹⁸

row 22:

row 23:

row 24:

I¹⁹

Notes:

¹ Harden corrected this from what looks like "D", to "C", maybe because he mistook the symbol for :
However, in the Chronicle article, no such mistake is evident:
Which worksheet came first?
² Harden appears to have originally considered and to be the same symbol.
The "F" appears to be overprinted on an "M", which is the translation of . Is the faintly visible right-facing tail of the "Q" an indicator of a correction?

³ Here, Harden shows three letters: A, S, and N:
The symbol translates to "A" later in the cipher text. But why did Harden write down "N"? Was he guessing that the word was "IN" instead of "IS"? Or did he think the symbol was which translates to "N"? Harden makes this same mistake later (see [15])
⁴ Harden seems to have originally thought that the symbol translated to Y.
The Chronicle worksheet shows a correction from "Y" to "M".

⁵ A subscript is written here on the Hardens' worksheet:
Is it the letter "S", or the number "5"? The Chronicle worksheet contains similar subscripts. But the subscript is indistinct on the clearer scan from Zodiac Unmasked:
⁶ Misspelling of "forest"

⁷ The symbol occurs eight times in the cipher text. Four of them translate to A, three of them translate to S, and one of them translates to I. Elsewhere in the cipher text, translates to S, and translates to I. This suggests Zodiac mistook his own triangle symbols when finalizing the cipher, or did it intentionally to try to confuse code breakers.

⁸ This appears to be an enciphering mistake. The mistaken portion is represented by the symbols which translate to "TUE". But replacing them with yields the correct spelling. Note the similarities of the symbols. Harden's corrections:

Also, the Chronicle article has the word as "hongertue". It's not clear how this mistake originated. The solution in the August 8 report from Vallejo PD includes the same mistake:
UPDATE: See annotation #20
⁹ The Hardens worksheet has this as "GIVESMETHEMOST", but the solution published in the Chronicle article has this as "GIVEERYETHEYOA". This is because Harden originally thought translated to "Y". See [4].
The solution published in the Vallejo Times-Herald article also shows "ERYETHEYOA" but omits "GIVE".
¹⁰ Misspelling of "experience"

¹¹ Harden mistook the symbol for , which decodes to "E".
The worksheet mistakenly marks this as an error. If you look at the cipher text printed in the SF Chronicle article and Vallejo Times-Herald article, the symbol does look like a :
¹² Some newspapers thought this part of the solution was too vulgar to publish. The Vallejo Times-Herald replaced "ROCKS OFF" with "THRILLS". The Sunday Times-Herald and Vallejo News Chronicle removed the entire sentence, "IT IS EVEN BETTER THAN GETTING YOUR ROCKS OFF WITH A GIRL."
¹³ The symbol occurs six times in the cipher text. Five of them translate to E, and one of them translates to T. Elsewhere in the cipher text, translates to T. Perhaps when finalizing the cipher, Zodiac mistook his for a .

¹⁴ Mispelling of "paradise"

¹⁵ The symbol occurs three times in the cipher text. Two of them translate to S, and one of them translates to A. Elsewhere in the cipher text, translates to A.
However, the Harden worksheet appears to show the mistake as "N" instead of "S", suggesting Harden may have originally thought the symbol was , which translates to "N".
See [3] where Harden again decodes the same symbol to "N".
¹⁶ A word is apparently missing here, right at the boundary between parts 2 and 3. Did it get "lost in the shuffle" as Zodiac split his message into three parts?

¹⁷ The Hardens worksheet shows a "Y" here, but the published solutions show an "S". Perhaps Harden originally thought the symbol was the symbol, which translates to "S". The worksheet appears to show Harden making the correction:

¹⁸ The symbol occurs fourteen times in the cipher text. Thirteen of them translate to I, and one of them translates to W. Elsewhere in the cipher text, translates to W. This again suggests Zodiac was confused about (or intentionally obfuscating) triangle-shaped symbols.

¹⁹ This final chunk of 18 letters, "EBEORIETEMETHHPITI", has no generally accepted interpretation. (More info).
Harden wrote the word "signature" above the symbols, perhaps as a guess to their meaning:
Harden might have also noted the multiple interpretations of the symbol, since there are annotations above and below it:
There also appears to be some additional erased letters above the plain text:
Are these attempts to rearrange the plain text?
²⁰ It was originally thought this symbol was a normal I. The Hardens apparently thought this. But upon closer inspection, the symbol appears to be the symbol.

Harden Key (cipher to plaintext):

Boxed symbols indicate polyphones

W 8

L 12

N 6

E 8

S 1 ⁸

S 6

A 7

T 8

T 10

O 1 ⁸

F 6

S 5

T 8

H 8

E 5 ¹³

T 1

N 7

I 11

F 5

G 12

A 6

O 7

I 10

B 9

E 9

O 9

U 10

E 8

V 6

O 6

C 10

D 3

O 5

X 1

I 9

P 7

A 5

E 6

M 16

R 7

N 6

T 8

E 8

N 4

D 4

H 8

A 1 ¹⁵

S 2

A 4 ⁷

I 1

S 3

I 13 ¹⁸

W 1

L 10

S 6

Y 8

L 11

K 6

R 5

E 8

Harden Key (plaintext to cipher):

Divisions between each of the three parts are indicated with
Symbols that occur in the last 18 cipher text positions are shown after this icon:

Letter	Count	Full Sequence
A	23	Note: If we retain the misspelling "ANAMAL", the sequence in Part 1 becomes: This preserves the cycle until it is interrupted in Part 2 of the cipher.
B	9
C	10
D	7
E	52	Note: The cycle is not broken until Part 3 of the cipher.
F	11	Note: The cycle is not broken until Part 3 of the cipher.
G	12
H	16	Note: The cycle repeats perfectly throughout the entire cipher.
I	44	Note: If we retain the misspelling "ANAMAL", then the cycle remains unbroken until Part 3 of the cipher.
J	0
K	6
L	33
M	16
N	23	Note: The cycle remains unbroken until Part 3 of the cipher.
O	28	Note: If we replace the mistaken symbol with , then the cycle remains unbroken until Part 3 of the cipher. UPDATE: Upon closer inspection, it appears the symbol really does appear as in the original cipher text.
P	7
Q	0
R	19	Note: The cycle remains unbroken until Part 3 of the cipher.
S	23	Note: If we replace with , and the mistaken symbol with , then the cycle is not broken until Part 3 of the cipher.
T	35	Note: If we replace the mistaken symbol with , then the cycle is not broken until Part 3 of the cipher.
U	10
V	6
W	9
X	1
Y	8
Z	0

Homophone cycles:

In the following image of the cipher text, all symbols that participate in unbroken homophone cycles are displayed in black. Symbols that do not follow a cycle pattern are displayed in gray. Cycles are considered after applying the transcription corrections analyzed above.

You can see how the cycle patterns mostly break down in Part 3 of the cipher. You can also see that the symbols intended to represent "L" often occur together, such as in the words "KILL", "THRILL", "WILL", "ALL", and "COLLECTING". If the killer had used predictable homophone cycles for "L", the meaning of those symbols would probably have been even more obvious. Nevertheless, the bigram

still occurs six times, which was a great clue for the Hardens to follow.

Differences between Harden Key and Concerned Citizen Key:

In Concerned Citizen key, decodes to N and W. In Harden solution, decodes only to W. Perhaps author of Concerned Citizen key mistook for , which decodes to N.
In Concerned Citizen key, decodes to L and T. In Harden solution, decodes only to T. It's not clear why Concerned Citizen key author included L.
In Harden solution, decodes to A and S. In the Concerned Citizen key, decodes only to S.
In Harden solution, decodes to F and decodes to M. In Concened Citizen key, these are combined into a single symbol, , which decodes to F, K, L and M. It is not clear why K and L are included in this mapping.
Concerned Citizen key mistakenly decodes as both F and X. The Harden solution indicates that X is mapped to symbol instead.
In the plaintext-to-cipher mapping above, symbols are presented in the order in which they appear in the cipher text. The same is true of the left column of the Concerned Citizen key, which shows plaintext-to-cipher mappings. However, the Concerned Citizen key does not show the cipher symbols for L in the correct order.
Hardens:
Concerned Citizen:
Coincidentally, the symbols for L in the cipher do not follow a strong homophone cycle like the others do.

Interpretation of FBI cryptanalysis of Concerned Citizen key:

FBI cryptanalysis results:

Interpretation:

Qc7 is the portion of the 408 cipher accompanying the SF Examiner letter.
Qc11 is the portion of the 408 cipher accompanying the SF Chronicle letter.
Qc15 is the portion of the 408 cipher accompanying the Vallejo Times-Herald letter.
Q18 is the Concerned Citizen key.
FBI examination determined that key is "substantially accurate", and a "generally valid decryption; equivalents for Qc7, 11, and 15."
The first (left) column of the key maps plaintext letters to cipher symbols.
The second (right) column of the key maps cipher symbols to multiple plaintext letters.
In the left column, plaintext letter X is mistakenly mapped to instead of .
FBI interpreted as cipher symbol .
FBI could not verify K and L to be valid mappings for cipher symbol .
F should be mapped to .
FBI could not verify N to be valid mapping for cipher symbol .
FBI could not verify O to be valid mapping for cipher symbol . However, you can see in the Harden solution that this arises from the transcription errors in the word "DANGEROUS" (see [8]).
FBI could not verify L to be valid mapping for cipher symbol .