python实现维吉尼亚加密法

import string,osdef   vigenereEncrypt(msg,key):    size = len(key)    result = []    cnt = 0    for i in msg:      if i.upper() in string.uppercase:        #offset相当于是 ki        offset = string.uppercase.find(key[cnt%size])        t = string.uppercase[(string.uppercase.find(i.upper())+offset)%26] #这里相当于是c1 = (mi+ki)(mod 26) ,t = c1        if i.isupper():          result.append(t)        else:          result.append(t.lower())        cnt+=1      else:        result.append(i)    return "".join(result)def   main():    msg = "Common sense is not so common"    cipher = vigenereEncrypt(msg,"PIZZA")#key = "PIZZA:    print cipherif   __name__=="__main__":    main()

##########Vigenere密码############ letter_list='ABCDEFGHIJKLMNOPQRSTUVWXYZ' #字母表 #根据输入的key生成key列表def Get_KeyList(key): key_list=[] for ch in key:  key_list.append(ord(ch.upper())-65) return key_list #加密函数def Encrypt(plaintext,key_list): ciphertext=""  i=0 for ch in plaintext: #遍历明文  if 0==i%len(key_list):   i=0  if ch.isalpha(): #明文是否为字母,如果是,则判断大小写,分别进行加密   if ch.isupper():     ciphertext+=letter_list[(ord(ch)-65+key_list[i]) % 26]    i+=1   else:    ciphertext+=letter_list[(ord(ch)-97+key_list[i]) % 26].lower()    i+=1  else: #如果密文不为字母,直接添加到密文字符串里   ciphertext+=ch return ciphertext #解密函数def Decrypt(ciphertext,key): plaintext=""  i=0 for ch in ciphertext: #遍历密文  if 0==i%len(key_list):   i=0  if ch.isalpha(): #密文为否为字母,如果是,则判断大小写,分别进行解密   if ch.isupper():    plaintext+=letter_list[(ord(ch)-65-key_list[i]) % 26]    i+=1   else:    plaintext+=letter_list[(ord(ch)-97-key_list[i]) % 26].lower()    i+=1  else: #如果密文不为字母,直接添加到明文字符串里   plaintext+=ch return plaintext if __name__=='__main__': print("加密请按D,解密请按E:") user_input=input(); while(user_input!='D' and user_input!='E'):#输入合法性判断  print("输入有误!请重新输入:")  user_input=input()  print("请输入密钥:") key=input() while(False==key.isalpha()):#输入合法性判断  print("输入有误!密钥为字母,请重新输入:")  key=input()  key_list=Get_KeyList(key)  if user_input=='D':  #加密  print("请输入明文:")  plaintext=input()  ciphertext=Encrypt(plaintext,key_list)  print("密文为:/n%s" % ciphertext) else:  #解密  print("请输入密文:")  ciphertext=input()  plaintext=Decrypt(ciphertext,key_list)  print("明文为:/n%s" % plaintext)