Babbage's successful cryptanalysis of the Vigenère cipher was probably achieved in 1854, soon after his spat with Thwaites, but his discovery went completely unrecognized because he never published it. The discovery came to light only in the twentieth century, when scholars examined Babbage's extensive notes. In the meantime, his technique was independently discovered by Friedrich Wilhelm Kasiski, a retired officer in the Prussian army. Ever since 1863, when he published his cryptanalytic breakthrough in Die Geheimschriften und die Dechiffrir-kunst {"Secret Writing and the Art of Deciphering"}, the technique has been known as the Kasiski Test, and Babbage's contribution has been largely ignored.
( Simon Singh )
[ The Code Book: The Science of ]
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