python 怎么实现维吉尼亚密码破解

维吉尼亚密码是一种古典密码，它使用多个凯撒密码组成一个更强大的加密算法。它可以使用一些技术进行破解，其中最有效的是使用基于频率分析的攻击技术。下面是一个简单的 Python 程序，以实现维吉尼亚密码的破解：

import collections

# 定义字母表
ALPHABET = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'

# 定义字母出现的频率
FREQUENCIES = {
    'A': 0.08167,
    'B': 0.01492,
    'C': 0.02782,
    'D': 0.04253,
    'E': 0.12702,
    'F': 0.02228,
    'G': 0.02015,
    'H': 0.06094,
    'I': 0.06966,
    'J': 0.00153,
    'K': 0.00772,
    'L': 0.04025,
    'M': 0.02406,
    'N': 0.06749,
    'O': 0.07507,
    'P': 0.01929,
    'Q': 0.00095,
    'R': 0.05987,
    'S': 0.06327,
    'T': 0.09056,
    'U': 0.02758,
    'V': 0.00978,
    'W': 0.02360,
    'X': 0.00150,
    'Y': 0.01974,
    'Z': 0.00074
}

def vigenere_decrypt(ciphertext, key):
    """
    使用维吉尼亚密码进行解密
    """
    plaintext = ''
    for i in range(len(ciphertext)):
        c = ciphertext[i]
        k = key[i % len(key)]
        p = ALPHABET[(ALPHABET.index(c) - ALPHABET.index(k)) % 26]
        plaintext += p
    return plaintext

def guess_key_length(ciphertext):
    """
    猜测密钥长度
    """
    distances = []
    for length in range(1, len(ciphertext)):
        blocks = [ciphertext[i:i+length] for i in range(0, len(ciphertext), length)]
        if len(blocks[-1]) != length:
            blocks.pop()
        distances.append(sum([hamming_distance(blocks[i], blocks[j]) / length for i in range(len(blocks)) for j in range(i+1, len(blocks))]) / len(blocks))
    return min(range(len(distances)), key=lambda x: distances[x]) + 1

def hamming_distance(s1, s2):
    """
    计算两个字符串之间的汉明距离
    """
    return sum([bin(ord(c1) ^ ord(c2)).count('1') for c1, c2 in zip(s1, s2)])

def guess_key(ciphertext, key_length):
    """
    猜测密钥
    """
    key = ''
    for i in range(key_length):
        block = ciphertext[i::key_length]
        counter = collections.Counter(block)
        max_letter = ''
        max_frequency = 0
        for letter, frequency in counter.items():
            if frequency > max_frequency:
                max_letter = letter
                max_frequency = frequency
        key += ALPHABET[(ALPHABET.index(max_letter) - ALPHABET.index('E')) % 26]
    return key

def main():
    ciphertext = 'VXGVRZJQYVYILGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPVGRGZRRQXVYHTJQYVYVZXRZGZPV'
    
    key_length = guess_key_length(ciphertext)
    key = guess_key(ciphertext, key_length)
    plaintext = vigenere_decrypt(ciphertext, key)
    
    print('猜测密钥长度:', key_length)
    print('猜测密钥:', key)
    print('解密结果:', plaintext)

if __name__ == '__main__':
    main()

这个程序首先使用基于汉明距离的技术来猜测密钥的长度，然后使用频率分析来猜测密钥的每个字符。最后，使用猜测的密钥来解密密文。