Cryptography 101
 By Melissa Salpietra
 Posted 07.01.07
 NOVA scienceNOW
You can make a message secret in countless different ways. One common way is to use a substitution cipher, in which one letter is substituted for another. Another is to employ a transposition cipher, in which the letters change position within the message. In this interactive, explore examples of a substitution cipher and two kinds of transposition cipher.
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 (Kryptos)
 Â© NOVA/WGBH Educational Foundation
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