Vigenere加密/解密时,把英文字母映射为0-25的数字再进行运算,并按n个字母为一组进行变换.算法定义如下:
设密钥 k =(k1,k2,k3…,kn),明文 m = (m1,m2,….mn)，则加密算法为:
Ek(m) = (c1,c2,…cn)
其中:c1 = (mi+ki)(mod 26),i=1,2,3…..n
解密算法为:
mi = (ci - ki)(mod 26), i = 1,2,…..n。
import string,os def 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 cipher if __name__=="__main__": main()
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