ConceptKasiski examination
Kasiski Examination
An attack against repeating-key polyalphabetic ciphers such as the Vigenère cipher. By analyzing the distances between repeated fragments in the ciphertext, it infers the key length and thereby reduces the polyalphabetic problem to several single-alphabet problems.
Timeline (last 90 days)
Oct 14
The weakness of the Vigenère cipher is that when the key length is short and the ciphertext is long enough, an attacker can infer the key length through the Kasiski test or the index of coincidence, thereby reducing the polyalphabetic problem to multiple single-alphabet problems to crack one by one.
Unverified50%