RC4

直接贴脚本了，非常简单且经典的加密算法

def rc4_ksa(key):
    """Key Scheduling Algorithm (KSA)"""
    key = [ord(c) for c in key]
    S = list(range(256))
    j = 0
    for i in range(256):
        j = (j + S[i] + key[i % len(key)]) % 256
        S[i], S[j] = S[j], S[i]
    return S

def rc4_prga(S, data_len):
    """Pseudo-Random Generation Algorithm (PRGA)"""
    i = j = 0
    keystream = []
    for _ in range(data_len):
        i = (i + 1) % 256
        j = (j + S[i]) % 256
        S[i], S[j] = S[j], S[i]
        K = S[(S[i] + S[j]) % 256]
        keystream.append(K)
    return keystream

def rc4_crypt(data: bytes, key: str) -> bytes:
    """Encrypt or decrypt data using RC4"""
    S = rc4_ksa(key)
    keystream = rc4_prga(S, len(data))
    return bytes([b ^ k for b, k in zip(data, keystream)])

key = "secretkey"
plaintext = "Hello, RC4!".encode()

# 加密
ciphertext = rc4_crypt(plaintext, key)
print("Ciphertext (hex):", ciphertext.hex())

# 解密（再次调用 rc4_crypt）
decrypted = rc4_crypt(ciphertext, key)
print("Decrypted:", decrypted.decode())