Codes in history

Alberti’s Disk

In 1467, architect Leon Battista Alberti described a curious device. It was a disk made up of two concentric rings: the outer ring engraved with a standard alphabet, and the inner ring, engraved with the same alphabet but written out of order. By rotating the inner ring and matching letters across the disk, a message could be enciphered, one letter at a time, in a fiendishly complex way.


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