1、ceasar


cipher="zhongguo"   #明文
move=3              #移位数
t=""                #密文
for i in cipher:
    if 'a'<=i<='z':
        t+=chr(ord('a')+((ord(i)-ord('a')+move)%26))
    elif 'A'<=i<='Z':
        t+=chr(ord('A')+((ord(i)-ord('A')+move)%26))
    else:
        t+=i
print(t)
        
#如果要解密的话，秘钥变为负数
#如zhongguo加密后得到ckrqjjxr
#现需要解密，则直接将move取-3即可

2、affine

#加密
cipher='zhongguo'#明文
t=''#密文
a=3
b=4 #E(x)=ax+b,gcd(a,26)
for i in cipher:
    if 'a'<=i<='z':
        t+=chr(ord('a')+((a*(ord(i)-ord('a'))+b)%26))
    elif 'A'<=i<='Z':
        t+=chr(ord('A')+((a*(ord(i)-ord('A'))+b)%26))
    else:
        t+=i
print(t)


#解密
t = 'bzurwwmu'  # 密文
cipher = ''  # 明文
a = 3
b = 4
for i in range(1, 26):
    if (i*a) % 26 == 1:
        a1 = i
        break
for i in t:
    if 'a' <= i <= 'z':
        cipher += chr(ord('a')+((a1*(ord(i)-ord('a')-b)) % 26))
    elif 'A' <= i <= 'Z':
        cipher += chr(ord('A')+((a1*(ord(i)-ord('A')-b)) % 26))
    else:
        cipher += i
print(cipher)