How the unbreakable vigenere cipher was broken

Download 1M+ code from https://codegive.com/74a78d5 breaking the vigenère cipher: from perceived unbreakability to cryptographic vulnerability the vigenère cipher, for a long time, held the reputation of being "le chiffre indéchiffrable" – the indecipherable cipher. it was considered unbreakable for centuries due to its use of a key phrase to shift the alphabet multiple times, making simple frequency analysis, which cracked the caesar cipher, ineffective. however, like all ciphers before modern cryptography, the vigenère cipher eventually succumbed to cryptanalysis. this tutorial will delve into the history, mechanics, and the critical techniques used to break the vigenère cipher, along with code examples in python to illustrate the concepts. **i. understanding the vigenère cipher** before we dissect how it was broken, let's solidify our understanding of the cipher's mechanism: 1. **polyalphabetic substitution:** the vigenère cipher is a polyalphabetic substitution cipher. this means, unlike a simple substitution cipher (like caesar), the same letter in the plaintext can be encrypted to different ciphertext letters, depending on its position. 2. **key phrase:** the key phrase is the backbone of the vigenère cipher. it's repeated as many times as necessary to match the length of the plaintext. each letter in the key phrase dictates the shift applied to the corresponding letter in the plaintext. 3. **vigenère square (tableau):** traditionally, the vigenère cipher is visualized using a vigenère square or tableau. this is a 26x26 grid where each row represents a caesar cipher with a different shift. the first row is the standard alphabet (a-z), the second row is the alphabet shifted by one (b-z, a), and so on. to encrypt, you find the row corresponding to the key letter and the column corresponding to the plaintext letter. the intersection of the row and column yields the ciphertext letter. **example:** * **plaintext:** the quick brown fox jumps over the lazy dog * **key:** key (repeated to match ... #VigenereCipher #Cryptography #python unbreakable Vigenère cipher Vigenère cipher broken cryptanalysis techniques cipher security historical encryption methods brute force attack frequency analysis polyalphabetic ciphers codebreaking history cryptography methods modern decryption mathematical attacks cipher weaknesses encryption vulnerabilities security implications