Onboard Lemp's ship was a small, portable encryption device used by U-boats to communicate with the German high command. Receiving coded messages on the location of enemy ships, prowling U-boats were constantly on the attack. British supply ships were especially hard hit. The loss of men and supplies was causing a massive strain on Britain's war efforts.
What was this encryption device? In 1923, Arthur Scherbius, a German engineer, introduced a
new product designed to help businesses conduct secure overseas communication. His company was incorporated as Chiffriermaschinen Aktiengesellschaft.
Although the German military would have been a potential customer for Scherbius, the military wasn't interested initially. By the time
Hitler and his party were elected to lead Germany, however, Scherbius had a
buyer for all the machines he could make.
Soon the encryption device - called
Enigma - was no longer commercially available to anyone outside the German military. Ideal for portable military use, Enigma was also simple to use. Its genius was the coupling of letters: they were constantly changed so the encrypted messages were never the same, making the code (with its billions of possible combinations) nearly impossible to break.
(Follow this link to an on-line Enigma simulator where you can experience
how it works. Be sure to click on the lower keyboard first; then type in a message in the space provided; then click on trace diagram to view the electrical circuitry of your message.)
Hitler, and many of his commanders, believed Enigma was invincible. They were wrong.