It’s been 50 years, but Charles David remembers it like it was yesterday.
David, an Allied cryptanalyst during World War II, spoke in front of a full crowd Thursday at a Pierson College Master’s Tea. He talked about the science of cryptology and his role in cracking the German’s field cipher, a type of code, during the war.
The cipher David’s team focused on was not the well-publicized high-grade Enigma code machine but rather the medium-grade field cipher, known to the Allies as the Non Indicator system.
David said that while the Enigma was used by top-level officials to transfer information, the Non Indicator system was also very important.
“It was not some minor system — it was the major German field cipher for the whole darn war,” David said.
Using slides to explain the nature of the Non Indicator system to the audience, David demonstrated the sophistication of the cipher that lulled the Germans into a false sense of security.
“I imagine they thought it was quite safe — but it wasn’t,” David said.
He added, however, that the system was incredibly difficult to break because of its double-encryption method and the German method of changing the cipher key every three hours.
“To the cryptanalyst it was diabolical, just absolutely devilish,” David said, showing the audience a sample encryption in order to illustrate the cipher’s complexity.
Even though the talk lasted almost two hours, members of the audience said they were captivated by David’s stories. One listener, Sebastian Shea ’04, said he was fascinated by David’s candor and in-depth analysis.
“He was really charming, and he’s obviously a genius,” Shea said. “It made me see that there’s a completely hidden other side to wars.”
Pierson Master Harvey Goldblatt agreed that it was intriguing to learn about the hidden side of the war, but said David’s speech had an added significance.
“There was definitely a double relevance to his talk today,” Goldblatt said. “Not only is it so important to learn about this unknown history, but it takes on a new meaning these days when one is thinking about questions of national security and trying to understand what goes on in the minds of those who are trying to penetrate our defenses.”
After enlisting in the Signal Corps, David became part of a top-secret field unit, the Signal Security Detachment D, in 1944. David said his unit traveled on the front line throughout France, Belgium and Germany, intercepting and decrypting German messages.
David said security within his field was so strong that often the cryptanalysts were not allowed to know what happened to the messages they deciphered. But he did tell one story about a message he intercepted.
The message, which came from German headquarters, ordered German troops to go into the woods of Luxembourg to rest for the night. Once the Allies knew of this movement, they were able to bomb the forests and destroy entire Axis divisions. Despite being behind the scenes, David said he and his fellow cryptanalysts played a large role in the war.
“We saved thousands of lives,” David said. “And we destroyed thousands of the enemies’ lives.”
After David left the war, he passed up an offer to remain with the Army and entered the business world, he said. Several years ago, when he realized that his field had been such a well-kept secret that even leading historians did not know about Signal Security Detachment D, he attempted to write an article about cryptology.
But the National Security Agency balked at the idea, he said. After he spoke at one of their symposiums, though, they agreed to let him publish an edited version.
In his closing, David expressed gratitude for his opportunities.
“When you go into the army, you don’t tell them what you’re doing, they tell you,” David said. “I was very lucky, and I appreciate the fact that Uncle Sam gave me this job.”