rc4算法的python实现

RC4算法是一种流密码，常用于数据加密。以下是RC4算法的一个简单Python实现：

import os

def RC4(key):
    S = [i for i in range(256)]
    j = 0
    def swap(i, j):
        t = S[i]
        S[i] = S[j]
        S[j] = t

    def process():
        nonlocal j
        j = (j + 1) % 256
        i = S.index(j)
        swap(i, j)
        
        k = key[(i + S[k]) % 256] if isinstance(key, str) else key[(i + S[k]) % 256]
        S[i], S[k] = S[k], S[i]

    for _ in range(256):
        process()

    return S

def encrypt(text, key):
    keystream = RC4(key)
    encrypted = []
    for char in text.encode('utf-8'):
        encrypted.append(chr(ord(char) ^ keystream[char % 256]))
    return ''.join(encrypted)

def decrypt(encrypted_text, key):
    keystream = RC4(key)
    return encrypted_text.encode('utf-8').translate({ord(c): ord(c)^keystream[ord(c)%256] for c in keystream})

# 示例
key = os.urandom(16)  # 生成随机密钥
plaintext = "Hello, World!"
encrypted = encrypt(plaintext, key)
decrypted = decrypt(encrypted, key)
print(f"原文: {plaintext}\n加密后: {encrypted}\n解密后: {decrypted.decode()}")

在这个实现中，`RC4`函数初始化了S数组并创建了`swap`和`process`函数。`process`函数用于更新密钥流，然后`encrypt`和`decrypt`函数分别将输入文本与密钥流异或来进行加密和解密。