Shifts in time: cryptography and randomness

Date: 12 April 2003.
Presenter: Sven Dietrich, Carnegie Mellon University.

In 1917, Gilbert Vernam developed the Vernam cipher, also commonly known as the one-time pad, a polyalphabetic substitution cryptosystem intended to thwart any adversary. J. Mauborgne, inspired by Vernam's work, extended the idea by replacing the repeated keystream ($2^5$ keys) with a non-repeating keystream sequence to create a one-time system. This one-time system requires a good source of random number sequences to be theoretically unbreakable, many of which were produced differently over time, e.g. by linear congruential generators of the form $x_i = (a{x}_{i-1} + b) mod n$, linear feedback shift registers, the Blum-Blum-Shub pseudo-random number generator, and even lava lamps. We observe the progress in the mathematics of producing these sequences throughout the 20th century and in the early 21st century.

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Last modified: 15 April 2003