In February 2004, 11-year-old Carlie Brucia was abducted and murdered in Sarasota, Florida. While in a county jail awaiting trial, the suspect in the case, Joseph Peter Smith, wrote an enciphered message to his brother (Figure 1). The seemingly random series of symbols and numbers was sent to the FBI for analysis. The FBI determined that Smith enciphered the message by replacing letters of the alphabet with a series of one- or two-character combinations of numerals and symbols. To further complicate decryption, he wrote the message from right to left, starting at the bottom of the page and working his way up. Despite these obstacles, FBI cryptanalysts were able to quickly decipher the message, which contained incriminating references to hiding evidence and moving the body. On November 17, 2005, the jury convicted Smith in the abduction and murder of Carlie Brucia.
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Cryptanalysis is the art of solving secret codes and ciphers. In courtrooms throughout history, cryptanalysis has played a key role in bringing criminals to justice. This article provides a historical overview of the role cryptanalysis has played in major cases over the past 400 years.
The Unabomber, 1978-1996
It is well known that criminals use codes and ciphers to communicate to others. However, when the Unabomber, Theodore Kaczynski (Figure 2), documented his deeds, it was not intended for anyone but himself. Kaczynski kept notebooks in which he logged his crimes, his feelings about them, and detailed plans for future crimes. These notes were found in a handwritten numerical code that he used to disguise his writing, which was in both English and Spanish (Birch, personal communication, 2005; Gibson 2000). His attempts at secrecy proved futile, however. When he was finally identified, the case against him was sealed by the decryption and translation of the content of those notebooks.
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The Zodiac Killer, 1966-?
Unlike the Unabomber, who did not want his …