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.
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.
Figure 2: Unabomber Theodore John Kaczynski
Unlike the Unabomber, who did not want his cryptic notations to be made public, the notorious Zodiac killer demanded that his ciphers be published in public newspapers. He thrived on the notoriety that the messages brought and even boasted of the strength of his ciphers. Despite his claims, Zodiac's most famous cipher (Figure 3) was broken within a few hours by a husband and wife team of amateur code breakers. Other Zodiac ciphers remain unsolved, and the Zodiac killer has never been brought to justice.
Figure 3: One of the Zodiac killer's enciphered messages
The inner workings of a Soviet spy ring were uncovered with the crack of a nickel by a Brooklyn newspaper delivery boy. When the unsuspecting boy dropped the nickel on the sidewalk, it split apart to reveal a microphotograph with a series of numbers (Figure 4). The numbered code, the product of a Soviet one-time pad encryption system, was not broken until 1957, after Soviet KGB officer Reino Hayhanen defected to the United States. The information he provided on Soviet codes and cryptosystems helped the FBI Laboratory break the code. The discovery of the hollow nickel and its contents eventually led to the conviction of a Soviet spy best known by his alias Rudolf Abel. In 1962 Abel was exchanged for American pilot Francis Gary Powers, whose U-2 spy plane had been shot down over the Soviet Union two years earlier (Federal Bureau of Investigation n.d.; Federal Bureau of Investigation 2004).
Figure 4: The hollow nickel used by Soviet spies to conceal messages
In 1937 the Canadian government requested the services of an American cryptanalyst to decipher messages written in Chinese by members of a suspected opium-smuggling ring. Five suspects from Vancouver, British Columbia, were found guilty of trading ammunition and guns for opium (National Security Agency n.d.; U.S. Coast Guard 2002). The cryptanalyst that the Canadians sought was Elizebeth Friedman. How did the Canadians know about this pioneer of U.S. cryptology? Three years earlier, she was the key U.S. government witness for the I'm Alone case between the United States and Canada.
The I'm Alone, a Canadian-flagged rumrunner, was sunk by the Coast Guard in the Gulf of Mexico, after its captain ignored an order to "heave to and be searched" (Mowry 2001). The Canadian government filed a $365,000 claim against the United States for the loss of its ship and cargo. To win the suit, the United States needed to prove that the ship was American-owned. Friedman's decryption of 23 messages helped prove that the ship was owned by two men from New York City. The matter was settled between the two countries with an apology and $50,000 (Mowry 2001).
Friedman's work in the I'm Alone case represented one of many ways she helped the U.S. government during Prohibition. She had been detailed to the Coast Guard to aid in the capture and prosecution of bootleggers following the passage of the Volstead Act, which enforced the 18th Amendment to the U.S. Constitution and prohibited the manufacture, sale, transportation, and possession of alcoholic beverages.
During Prohibition, Friedman decrypted thousands of messages and was able to link the ringleaders of numerous bootleg operations with suspected vessels. Friedman's cryptanalytic work and testimony helped convict numerous rumrunners, including a large, powerful smuggling syndicate that ran a virtual smuggling monopoly in the Gulf of Mexico and on the West Coast (Mowry 2001).
Elizebeth Friedman was only half of the greatest marriage in the history of cryptology. Her husband, William Friedman, made significant contributions to the field of cryptanalysis, including breaking the Japanese diplomatic cipher (codenamed "Purple") during World War II. Although William Friedman is best known for his wartime work, he also used his skills to support law enforcement. Both William and Elizebeth Friedman hold a place in the National Security Agency's National Cryptologic Museum's Hall of Honor (National Security Agency n.d.).
In 1924 William Friedman testified before a congressional committee regarding coded telegrams exchanged during the Teapot Dome scandal (Herzog 2000), which involved the secret leasing of U.S. government-owned lands to private developers in exchange for bribes. The oil-rich land was meant to provide U.S. naval ships with fuel in a national emergency. Then-Secretary of the Interior Albert Fall first got jurisdiction over the land transferred from the Department of the Navy to the Department of the Interior, then secretly leased the land to two oil companies. Friedman's decryption of the coded telegrams led to a prison sentence for Fall and the resignation of other top government officials, including the Secretary of the Navy and the Attorney General (Bennett 1999; Herzog 2000).
On April 14, 1865, actor John Wilkes Booth shot President Abraham Lincoln as he watched a play at Ford's Theatre in Washington, D.C. Lincoln died early the next morning. Did Booth work with a small group of coconspirators, or did he have the backing and approval of the Confederate government and its president, Jefferson Davis? Although controversy remains, some historians are convinced that Davis may have supported a plan to bomb the White House or kidnap Lincoln, if not to kill him at the theater (Linder 2002a; Linder 2002b; Wilkes, April 20, 2005; Wilkes, April 27, 2005).
Transcripts from the Lincoln Assassination Conspiracy Trial detail the use of ciphers between Booth, his fellow conspirators, and the Confederate government in Richmond, Virginia. According to the prosecuting attorney, the machine used to encrypt these ciphers was found in a room of the Confederate State Department in Richmond. An encrypted letter found in Booth's possession was written using the same machine and, in the prosecutor's opinion, further confirmed that Jefferson Davis and the Confederate government were involved in the plot (Linder 2002b).
The Military Commission convicted seven coconspirators. Four were put to death, including Mary Surratt, the first woman ever executed by the U.S. government. Three were sentenced to life in prison, and one received six years. An eighth coconspirator, John Surratt, who fled the United States following the assassination, was captured and then tried by a civilian court, which resulted in a hung jury. Together with a little-known Confederate agent named Sarah Slater, Surratt is believed to have transported enciphered messages from the Confederate government in Richmond to other Confederate agents in Canada. It is believed that these messages approved the assassination plot against Lincoln (Linder 2002a; Linder 2002b; Smith 2006).
Interestingly, Union officials had been reading Confederate ciphers throughout the Civil War. The same cannot be said for Confederate officials. They were so desperate in their decryption attempts that they published the Union's encrypted messages in Southern newspapers, asking readers for help in deciphering them (Encyclopaedia Britannica 2006).
The oldest documented case of cryptanalysis in law enforcement occurred more than 400 years ago. In the 16th century, Mary, Queen of Scots, plotted to assassinate her cousin, Elizabeth, Queen of England. She transcribed many communications to her coconspirators using ciphers (Figure 5) and hoped they would be secure. Fortunately for Queen Elizabeth, the plot was uncovered with the unraveling of the secret communications. Unfortunately for Mary, the deciphered messages revealed the conspiracy and led to her conviction and death sentence (The National Archives n.d.; Singh 1999).
Figure 5: Mary, Queen of Scots, used enciphered messages such as this one in her plan to assassinate her cousin, Queen Elizabeth of England.
Source: The National Archives, U.K. Reprinted with permission.
Cryptanalysis has played a critical role in law enforcement for the past 400 years. Although the methods and techniques used by criminals change over time, the need for secret communication ensures that criminals will continue to use codes and ciphers. Law enforcement cryptanalysts will continue to engage in the battle of wits between criminal code makers and law enforcement code breakers.
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Singh, Simon. The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography. Doubleday, New York, New York, 1999, pp. 32–44.
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