cryptography and murder – the zodiac killer
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Cryptography and Murder – The Zodiac Killer. The Case. Serial killer active in the San Francisco area 1967 – 1974 (at least) Linked to 7 murders, but claimed many more Never caught Police investigation closed in 2004 Lots of theories and speculations around the case. - PowerPoint PPT PresentationTRANSCRIPT
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Cryptography and Murder –The Zodiac Killer
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The Case
Serial killer active in the San Francisco area 1967 – 1974 (at least) Linked to 7 murders, but claimed many more Never caught Police investigation closed in 2004 Lots of theories and speculations around the
case
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This is the Zodiac speaking...
Wrote many letters (at least 18) to the police and to newspapers in the SF area
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Ciphers
Four letters contained ciphers
Appear to be substitution ciphers, but with more cipher text symbols than ordinary letters
Two of them contain too little cipher text to be solved
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408 Cipher
First cipher the Zodiac sent
Was divided in three parts and sent to three
different newspapers All three parts published
on the front pages Solved in a week by a
high school teacher and his wife
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How Did They Do It?
Knew the killer had a big ego, assumed he would start with ’I’
Assumed the word ’kill’ would appear several times
This was 1969 – only pencil and paper!
Donald Harden
http://www.zodiackiller.com/donaldharden.mp3
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Part 1 Character Cipher
Cipher Key
Cipher Solution
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Caesar Ciphers
Method used by Romans for hiding messages; called “Caesar Ciphers”
An easy way to hide messages is to shift each letter of the alphabet forward or backward a number of spaces.
Let’s shift the alphabet backward by three and code the following message:FORENSIC SCIENCE USES
CRYPTOGRAPHY TO SOLVE CRIMES.
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FORENSIC SCIENCE USES CRYPTOGRAPHY TO SOLVE CRIMES.
Plain
Cipher
A B C D E F G H I J K L M
D E F G H I J K L M N O P
N O P Q R S T U V W X Y Z
Q R S T U V W X Y Z A B C
Solution:
IRUHQVLF VFLHQFH XVHV FUBSWRJUDSKB WR VROYH FULPHV.
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Caesar Ciphers
Answer 3: Do number four! Answer 4:
ZKBD YP DRO JYNSKM MYNO RKC LOOX LBYUOX
The Zodiac killer is still at large.
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This is quite cumbersome so let’s look at letter frequencies to speed this up.
Most commonly used letters in descending order of frequency: E-T-A-O-N-R-I-S-H-D-L-F-C-U- M-G-P-Y-W-B-V-K-X-J-Q-Z
Do number 5! Answer 5:
The Zodiac killer uses complex ciphers.
HVS NCRWOQ YWZZSF IGSG QCADZSL QWDVSFG
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Substitution Ciphers It would have been simple to break the code if the
Zodiac killer had used a Ceasar cipher, but he didn’t.
He used a substitution cipher. In a substitution cipher, either the alphabet is not in order or each letter of the alphabet is represented by a symbol.
Do number 6! Answer 6: Donald Harden solved a zodiac cipher.