古典密码之维吉尼亚密码

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维吉尼亚密码是使用一系列凯撒密码组成密码字母表的密码算法，属于多表密码的一种简单形式。

维吉尼亚密码是使用一系列凯撒密码组成密码字母表的密码算法，属于多表密码的一种简单形式。

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class VigenereCipher:
    def __init__(self):
        self.letter_map1 = {'A':0, 'B':1, 'C':2, 'D':3, 'E':4, 'F':5, 'G':6, 'H':7, 'I':8, 'J':9, 'K':10, 'L':11, 'M':12, 'N':13, 'O':14, 'P':15, 'Q':16, 'R':17, 'S':18, 'T':19, 'U':20, 'V':21, 'W':22, 'X':23, 'Y':24, 'Z':25, 0:'A', 1:'B', 2:'C', 3:'D', 4:'E', 5:'F', 6:'G', 7:'H', 8:'I', 9:'J', 10:'K', 11:'L', 12:'M', 13:'N', 14:'O', 15:'P', 16:'Q', 17:'R', 18:'S', 19:'T', 20:'U', 21:'V', 22:'W', 23:'X', 24:'Y', 25:'Z'}
        self.letter_map2 = {'a':0, 'b':1, 'c':2, 'd':3, 'e':4, 'f':5, 'g':6, 'h':7, 'i':8, 'j':9, 'k':10, 'l':11, 'm':12, 'n':13, 'o':14, 'p':15, 'q':16, 'r':17, 's':18, 't':19, 'u':20, 'v':21, 'w':22, 'x':23, 'y':24, 'z':25, 0:'a', 1:'b', 2:'c', 3:'d', 4:'e', 5:'f', 6:'g', 7:'g', 8:'i', 9:'j', 10:'k', 11:'l', 12:'m', 13:'n', 14:'o', 15:'p', 16:'q', 17:'r', 18:'s', 19:'t', 20:'u', 21:'v', 22:'w', 23:'x', 24:'y', 25:'z'}

    def encryption(self, plaintext, key):
        '''
        加密函数
        '''
        cyphertext = []
        key_list = list(key)
        cnt = 0
        for i in plaintext:
            if cnt % len(key_list) == 0:
                cnt = 0
            if i.isalpha():
                if i.isupper():
                    cyphertext.append(self.letter_map1[(self.letter_map1[i] + self.letter_map1[key_list[cnt].upper()])%26])
                if i.islower():
                    cyphertext.append(self.letter_map2[(self.letter_map2[i] + self.letter_map2[key_list[cnt].lower()])%26])
                cnt += 1
            else:
                cyphertext.append(i)
        return ''.join(cyphertext)

    def decryption(self, cyphertext, key):
        '''
        解密函数
        '''
        plaintext = []
        key_list = list(key)
        cnt = 0
        for i in cyphertext:
            if cnt % len(key_list) == 0:
                cnt = 0
            if i.isalpha():
                if i.isupper():
                    plaintext.append(self.letter_map1[(self.letter_map1[i] - self.letter_map1[key_list[cnt].upper()])%26])
                if i.islower():
                    plaintext.append(self.letter_map2[(self.letter_map2[i] - self.letter_map2[key_list[cnt].lower()])%26])
                cnt += 1
            else:
                plaintext.append(i)
        return ''.join(plaintext)

t_plain = '12.25 HappyBirthday!'
t_key = 'AMAZE'
t = VigenereCipher()
print('明文是：', t_plain)
t_cypher = t.encryption(t_plain, t_key)
print('密文是：', t_cypher)
t_result = t.decryption(t_cypher, t_key)
print('解密结果是：', t_result)
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