NSA: American Cryptology During the Korean War This is a declassified National

Declassified: American Cryptology During the Korean War This is a declassified National Security Agency record, released through The Black Vault, detailing the state of American cryptology during the Korean War. The document was written by Dr. Thomas R. Johnson, a 35-year veteran of cryptology operations, and is unclassified in its entirety. The document was released in July 2001, as part of a larger declassification effort by the NSA. The agency has recently declassified a few historical summaries related to the Korean War, but has not yet begun to release any reports from the war itself. American Cryptology During the Korean War With Korean war cryptology, we are still in the early stage of declassification fifty years after the outbreak of the war. 99 Dr. Thomas R. Johnson is a 35-year veteran of cryptology operations, Currently associated with CIA's Center for the Study of Intelligence, he is the author of a classified four-volume history of American cryptology during the Cold War. The Korean War was a significant conflict that began on June 25, 1950, when North Korean forces invaded South Korea. In response to a United Nations call for troops to restore peace, the United States committed ground, air, and naval forces to the conflict. The war ultimately ended with an armistice signed on July 27, 1953, which provided for the continued presence of US troops on Korean soil. The United States suffered more than 140,000 casualties during the engagement. A peace treaty has never been signed, and Allied silence about the role of cryptology in World War II was broken in 1974 by the publication of Frederick Winterbotham's The Ultra Secret. The world had waited almost 30 years for the beginning of a declassification program for World War II communications intelligence. A few spare historical accounts written during and immediately after the war represented most of what the National Security Agency and the UK Government Communications Headquarters had been willing to divulge. With Korean war cryptology, we are still in the early stage of declassification fifty years after the outbreak of the war. NSA has recently declassified a few historical summaries, but has not yet begun to release any reports from the war itself. So what do we know about cryptology in Korea? Some of our knowledge preceded the official declassification effort. When Clay Blair wrote his history of the Korean war in the 1980s, he incorporated some tantalizing bits and pieces about the role of exploited North Korean messages, especially as it related to the Pusan perimeter. More recently, researcher Matthew Aid has written about the role of US human and signals intelligence in the Korean War. Aid's work has shed light on the importance of cryptology during the conflict. The Korean War can best be understood in terms of World War II, which has been described as a "SIGINT War." By the end of the war, the Americans and British, with help from the Canadians and Australians, were able to read most of the important cryptographic systems that the Axis nations employed. The loss of talent was accompanied by a catastrophic budgetary collapse. The lack of resources was compounded by bureaucratic infighting. A wartime feud between Army and Navy cryptologists continued into the post-war period. Then a new group—the Air Force Security Service (AFSS)—joined the fray. Although the AFSS began as a weak sister, it benefited from the Air Force's ability to get money from Congress and soon became the largest of the three service cryptologic agencies. It also became the most parochial, separating itself from the cryptologic community by physical as well as psychic distance by setting up its headquarters in San Antonio, Texas. Amid all the bickering came signs of professional failure. Until 1948, the Army and Navy had been reading many of the codes of the new prime target, the Soviet Union. Then, in the space of less than a year, the lights went out. The USSR changed everything—its codes and ciphers, its communications procedures, and the very equipment that it used. The cryptologic community referred to what had happened as Black Friday. In fact, it didn't happen on a Friday, but evolved over several months. The bottom line was the same: the cornucopia of exploitable messages disappeared and Washington was caught short. This is what the public record looks like at its most ordinary. Storyflo.com. The declassified document is available at archive.org/download/us-china-intel-CI02337/CI02337_djvu.txt.