Friedrich Kasiski

Friedrich Wilhelm Kasiski ( born November 29, 1805 in Pomerania, West Prussia, † May 22 1881 in Pommern ) was a Prussian major and wore as a cryptographer significantly to deciphering the Vigenere cipher.

Kasiski published in 1863 in his book The Secret codes and the Dechiffrir - art test for cryptanalysis of the Vigenere cipher, which is known as Kasiski test today. The method used Kasiski could determine the length of the cipher key word. To this end, he searched the ciphertext after repetitive sequences of letters. From the distances between the character strings he calculated greatest common divisor, which then produces the presumed key length. The Kasiski test is very effective when decrypting of text that are encrypted with the Vigenere cipher, despite its simplicity.

Some years earlier Charles Babbage developed a method to filter out the key from Vigenere cipher texts. However, he had not published, so his records were seen only after his death his findings.

From 1866 Kasiski built up a collection of antiquities from around Pommern, was the basis of the 1914 Historical Museum opened Pommern.

Works

• The secret codes and Dechiffrir art. Berlin 1863