古典密码之凯撒密码

该密码以被古罗马皇帝凯撒使用而闻名,用于和将军们进行联系。其基本思想是:通过把字母移动一定的位数来实现加密和解密。

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class CaesarCipher:
def __init__(self):
self.letter_map = {'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'}

def encryption(self, plaintext, key):
'''
加密函数
'''
plaintext = plaintext.upper()
cyphertext = []
for i in plaintext:
if i.isalpha():
cyphertext.append(self.letter_map[(self.letter_map[i] + key)%26])
else:
cyphertext.append(i)
return ''.join(cyphertext)

def decryption(self, cyphertext, key):
'''
解密函数
'''
cyphertext = cyphertext.upper()
plaintext = []
for i in cyphertext:
if i.isalpha():
plaintext.append(self.letter_map[(self.letter_map[i] - key)%26])
else:
plaintext.append(i)
return ''.join(plaintext)

t_plain = '12.25 HappyBirthday!'
t_key = 3
t = CaesarCipher()
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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