Doppler (cryptology)

In cryptology and especially in cryptanalysis, character sequences that appear several times in a text are called Dopplers .

Depending on the length, one speaks of bigram Dopplers (length 2), trigram Dopplers (length 3), tetragram Dopplers (length 4) and so on. The appearance of Dopplers in a ciphertext is a possible point of attack for a code breaker , which can be used as an introduction to deciphering . For example, by analyzing Dopplers, also known as Doppler searches , the period of a polyalphabetic substitution , such as the Vigenère cipher, can be deduced. The procedure was explained by the retired Prussian infantry major and cryptologist Friedrich Wilhelm Kasiski (1805–1881) in his book Die Geheimschriften und die Dechiffrir-Kunst , published in Berlin in 1863 . This cryptanalytic method is still known today under his name as the Kasiski test .

literature

Friedrich L. Bauer : Deciphered secrets - methods and maxims of cryptology . Springer, Berlin 2000 (3rd edition), ISBN 3-540-67931-6 .

Web links

The secret scripts and the art of deciphering Some pages from Kasiski's book as a scan. Retrieved August 26, 2016.

Individual evidence

↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin et al. 2000, p. 321.

[1] Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin et al. 2000, p. 321.