Gilbert Vernam - One-time Pad

One-time Pad

Shortly thereafter, Joseph Mauborgne, at that time a captain in the US Army Signal Corps, proposed, in addition, that the paper tape key contain random information. The two ideas, when themselves combined, implement an automatic form of the one-time pad, though neither inventor used the name then. It was patented in the mid-1920s.

Claude Shannon, also at Bell Labs, proved that the one-time pad is unbreakable in his World War II research that was later published in October 1949. He also proved that any unbreakable system must have essentially the same characteristics as the one-time pad: the key must be truly random, as large as the plaintext, never reused in whole or part, and kept secret.