在密码学中，RC4（来自Rivest Cipher 4的缩写）是一种流加密算法，密钥长度可变。它加解密使用相同的密钥，因此也属于对称加密算法。RC4是有线等效加密（WEP）中采用的加密算法，也曾经是TLS可采用的算法之一。本文直接给出加密解密代码，看图，看注释！
运行结果：
捕获.PNG
加密源码：
import base64
def rc4_main(key = "init_key", message = "init_message"):
# print("RC4加密主函数")
s_box = rc4_init_sbox(key)
crypt = str(rc4_excrypt(message, s_box))
return crypt
def rc4_init_sbox(key):
s_box = list(range(256)) # 我这里没管秘钥小于256的情况，小于256不断重复填充即可
# print("原来的 s 盒：%s" % s_box)
j = 0
for i in range(256):
j = (j + s_box[i] + ord(key[i % len(key)])) % 256
s_box[i], s_box[j] = s_box[j], s_box[i]
# print("混乱后的 s 盒：%s"% s_box)
return s_box
def rc4_excrypt(plain, box):
# print("调用加密程序成功。")
res = []
i = j = 0
for s in plain:
i = (i + 1) % 256
j = (j + box[i]) % 256
box[i], box[j] = box[j], box[i]
t = (box[i] + box[j]) % 256
k = box[t]
res.append(chr(ord(s) ^ k))
# print("res用于加密字符串，加密后是：%res" %res)
cipher = "".join(res)
# print("加密后的字符串是：%s" %cipher)
# print("加密后的输出(经过编码):")
# print(str(base64.b64encode(cipher.encode('utf-8')), 'utf-8'))
return (str(base64.b64encode(cipher.encode('utf-8')), 'utf-8'))
# rc4_main("123456sh","123456sh")
解密源码：
import base64
def rc4_main(key = "init_key", message = "init_message"):
# print("RC4解密主函数调用成功")
s_box = rc4_init_sbox(key)
crypt = rc4_excrypt(message, s_box)
return crypt
def rc4_init_sbox(key):
s_box = list(range(256)) # 我这里没管秘钥小于256的情况，小于256不断重复填充即可
# print("原来的 s 盒：%s" % s_box)
j = 0
for i in range(256):
j = (j + s_box[i] + ord(key[i % len(key)])) % 256
s_box[i], s_box[j] = s_box[j], s_box[i]
# print("混乱后的 s 盒：%s"% s_box)
return s_box
def rc4_excrypt(plain, box):
# print("调用解密程序成功。")
plain = base64.b64decode(plain.encode('utf-8'))
plain = bytes.decode(plain)
res = []
i = j = 0
for s in plain:
i = (i + 1) % 256
j = (j + box[i]) % 256
box[i], box[j] = box[j], box[i]
t = (box[i] + box[j]) % 256
k = box[t]
res.append(chr(ord(s) ^ k))
# print("res用于解密字符串，解密后是：%res" %res)
cipher = "".join(res)
# print("解密后的字符串是：%s" %cipher)
# print("解密后的输出(没经过任何编码):")
return cipher
# rc4_main("123456sh", "ABHCum92PMOXwqI=")
