Райтап на задачу «Послание от Француза»

Wmits, izxdiamo! Gsj tbnx ipfa ftpfvh xv Pimcb-Mwygkxqr-hco-Amdcim. Mi abmqtl futdzqiri, al Q htkflis bl ziicov mi. JroGIN{A0VX_U0ZD3B_XW3_S3V}

import string
from collections import Counter


def quick_key_length_analysis(ciphertext):
    cipher_letters = ''.join(c.upper() for c in ciphertext if c.isalpha())
    
    for key_length in range(1, 16):
        subsequences = ['' for _ in range(key_length)]

        for i, char in enumerate(cipher_letters):
            subsequences[i % key_length] += char

        ics = []
        for subseq in subsequences:
            if len(subseq) > 1:
                n = len(subseq)
                freq = Counter(subseq)
                ic = sum(count * (count - 1) for count in freq.values()) / (n * (n - 1))
                ics.append(ic)

        if ics:
            avg_ic = sum(ics) / len(ics)
            bar = "█" * int(avg_ic * 150)
            marker = " 🎯" if 0.060 < avg_ic < 0.070 else ""
            print(f"Длина {key_length:2d}: {avg_ic:.4f} {bar}{marker}")

ciphertext = "Wmits, izxdiamo! Gsj tbnx ipfa ftpfvh xv Pimcb-Mwygkxqr-hco-Amdcim. Mi abmqtl futdzqiri, al Q htkflis bl ziicov mi. JroGIN{A0VX_U0ZD3B_XW3_S3V}"
quick_key_length_analysis(ciphertext)

import string
import itertools
import time

def vigenere_decrypt(ciphertext, key):
    result = []
    key = key.upper()
    key_length = len(key)
    key_as_int = [ord(i) - ord('A') for i in key]

    key_index = 0
    for char in ciphertext:
        if char.isalpha():
            base = ord('A') if char.isupper() else ord('a')
            shift = key_as_int[key_index % key_length]
            decrypted_code = (ord(char) - base - shift) % 26
            decrypted = chr(decrypted_code + base)
            result.append(decrypted)
            key_index += 1
        else:
            # Неалфавитные символы добавляем без изменений
            result.append(char)

    return ''.join(result)

ciphertext = "Wmits, izxdiamo! Gsj tbnx ipfa ftpfvh xv Pimcb-Mwygkxqr-hco-Amdcim. Mi abmqtl futdzqiri, al Q htkflis bl ziicov mi. JroGIN{A0VX_U0ZD3B_XW3_S3V}"
known_plaintext = "BugCTF"

iteration = 0
start_time = time.time()
alphabet = string.ascii_uppercase

for key_tuple in itertools.product(alphabet, repeat=5):
    iteration += 1
    key = ''.join(key_tuple)
    decrypted = vigenere_decrypt(ciphertext, key)
    
    if known_plaintext in decrypted:
        elapsed_time = time.time() - start_time
        print(f"\nКлюч найден на итерации {iteration} за {elapsed_time:.2f} секунд")
        print(f"🔑 Ключ: {key}")
        print(f"📜 Расшифрованный текст: {decrypted}")
        break