Colossus and Other Early Cryptologic Machines

In the early 1940s the German military introduced several new cryptographic teletypewriters known under the name “Geheimschreiber.” These machines offered on-line encryption and decryption. Text could be typed directly into the machine, automatically converted to encrypted text, and sent directly to the transmitter. In addition to security, these “secret writers” provided the Germans with the ability to encrypt large volumes of text at high speeds.