Cryptanalysis of the Vigenère Cipher: How Kasiski's Test Reveals the Secret 🕵️‍♂️

The Vigenère Cipher was invented in the 16th century to encrypt secret texts. It was long regarded as a secure method and unbreakable. In 1863, however, the Prussian infantry major Friedrich Wilhelm Kasiski published a method for determining the key length used in encryption. This made the Vigenère encryption vulnerable. The video uses an example to show how the Kasiski test is carried out and what other attack possibilities it offers for breaking the ciphertext. 0:00 Backstory 0:17 Kasiski examination 2:00 Grouping ciphertext into columns 2:12 Frequency analysis 3:19 Analyzing text snippets that occur multiple times 4:00 Brute force plaintext attack 5:52 Context-sensitive plaintext attack 6:40 Ciphertext cracked 7:11 Conclusion 7:35 Vulnerabilities 8:00 Security measures