cryptology: Quick Facts

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A Vigenere cipher table displays the alphabet in both the top row and left column, with rows shifted to create a grid for encryption and decryption. Highlighted letters illustrate how to use the table. An explanation and example using the words cipher, key, and plaintext appears to the right.

Letter frequency analysis of a Vigenère cipher

Frequency distribution for plaintext and its repeated-key Vigenère cipher

Diagram explaining the German ADFGVX cipher from World War I, showing a biliteral substitution array, examples of plaintext and intermediate ciphertext in red, and a transposition matrix with final ciphertext in blue.

A circular cipher disk labeled Signal Corps U.S. Army, featuring two concentric rings of letters used for manual encryption by rotating the inner ring to align different alphabets.

Hagelin M-209 U.S. cipher machine with its case open, showing exposed gears, rotors, and mechanical components used for encoding messages during World War II.

Purple cipher machine

Jade cipher machine

DES flow diagram

How William Friedman Tried to Prove That Francis Bacon Wrote Shakespeare's Plays

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Topics

cryptanalysis cryptography decryption information theory data encryption mathematics analysis probability theory computer science combinatorics algebra statistics geometry automata theory set theory trigonometry

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Key People

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William F. Friedman

American cryptologist

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Elizebeth S. Friedman

American cryptologist

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Agnes Meyer Driscoll

American cryptologist

Yardley, Herbert Osborne

Herbert Osborne Yardley

American cryptologist

A botanical illustration from the Voynich manuscript, a codex, scientific or magical text in an unidentified language, in cipher; end of the 15th or during the 16th century (?).

Codes, Secrets, and Ciphers Quiz