Gilbert Vernam

Gilbert Sandford Vernam was a Worcester Polytechnic Institute graduate of 1914 and an engineer with AT&T Bell Labs who in 1917 invented an additive polyalphabetic stream cipher and later co-invented an automated one-time pad cipher. Born in 1890, he proposed a teleprinter cipher in which a previously prepared key, kept on paper tape, is combined character by character with the plaintext message to produce the ciphertext, and the same key applied again recovers the plaintext. The combining function he specified in United States patent 1,310,719, issued in 1919, is the exclusive or operation. He later worked for the Postal Telegraph Company, became an employee of Western Union when that company acquired Postal in 1943, and worked largely on automatic switching systems for telegraph networks. He died in 1960.