Friedrich Kasiski

Friedrich Wilhelm Kasiski was a German officer, cryptographer, and archaeologist. In 1863 he published Die Geheimschriften und die Dechiffrir-Kunst, a book that described a practical attack on repeating-key polyalphabetic substitution ciphers.

The Kasiski examination

The method studies distances between repeated ciphertext fragments to infer likely key periods. It became known as the Kasiski examination and is still taught when explaining attacks on Vigenère-style systems.

Historical place

Kasiski’s contribution matters because it turns a cipher’s repeated structure into evidence for analysis. Later work may have independently anticipated aspects of the approach, but Kasiski’s was the influential published account.

In memoriam

Kasiski died in 1881. His name endures in the classical cryptanalytic technique associated with his 1863 publication.

Timeline

• 1805-11-29Born in Schlochau, Prussia.
• 1852Retires from active military service with the rank of major.
• 1863Publishes Die Geheimschriften und die Dechiffrir-Kunst.
• 1863Publishes the method now called the Kasiski examination.
• 1881-05-22Dies in Neustettin, Germany.