用python实现并打包成一个接口函数 基于Feistel结构构造一个分组密码算法。要求： 1、 分组长度 = 128 bit 2、 主密钥长度 >= 128 bit 3、 轮数 >= 8 4、 轮函数的设计要用到LFSR

由于该算法需要使用到伪随机数生成函数和LFSR算法，所以需要先安装相应的Python库，比如NumPy和BitVector。以下是实现分组密码算法并打包成接口函数的代码示例：

import numpy as np
from BitVector import BitVector

# Feistel结构的轮函数，使用LFSR算法生成伪随机数序列
def round_function(right, round_key):
    lfsr = BitVector(bitstring=round_key)
    for i in range(8):
        lfsr.shift_left(1)
        lfsr[-1] = lfsr[0] ^ lfsr[2] ^ lfsr[3] ^ lfsr[5]
    return lfsr.get_bitvector_in_hex()[:16] ^ right

# Feistel结构的加密函数
def feistel_encrypt(block, sub_keys, rounds):
    left = block[:64]
    right = block[64:]
    for i in range(rounds):
        round_key = sub_keys[i]
        temp = right
        right = left ^ round_function(right, round_key)
        left = temp
    return right + left

# Feistel结构的解密函数
def feistel_decrypt(block, sub_keys, rounds):
    left = block[:64]
    right = block[64:]
    for i in range(rounds-1, -1, -1):
        round_key = sub_keys[i]
        temp = left
        left = right ^ round_function(left, round_key)
        right = temp
    return left + right

# 加密文件
def encrypt_file(input_file, output_file, key):
    with open(input_file, 'rb') as f:
        plaintext = f.read()
    blocks = [BitVector(bytes=plaintext[i:i+16]) for i in range(0, len(plaintext), 16)]
    sub_keys = [BitVector(intVal=int(key[i:i+16], 16), size=64) for i in range(0, len(key), 16)]
    ciphertext = b''
    for block in blocks:
        ciphertext += feistel_encrypt(block, sub_keys, 8).get_bytes_from_bitvector()
    with open(output_file, 'wb') as f:
        f.write(ciphertext)

# 解密文件
def decrypt_file(input_file, output_file, key):
    with open(input_file, 'rb') as f:
        ciphertext = f.read()
    blocks = [BitVector(bytes=ciphertext[i:i+16]) for i in range(0, len(ciphertext), 16)]
    sub_keys = [BitVector(intVal=int(key[i:i+16], 16), size=64) for i in range(0, len(key), 16)]
    plaintext = b''
    for block in blocks:
        plaintext += feistel_decrypt(block, sub_keys, 8).get_bytes_from_bitvector()
    with open(output_file, 'wb') as f:
        f.write(plaintext)
        
# 打包成接口函数
def feistel_cipher(input_file, output_file, key, mode='encrypt'):
    if len(key) < 16:
        raise ValueError('Key length should be at least 16 hex digits')
    if len(key) % 16 != 0:
        key = key.ljust(len(key) + 16 - len(key) % 16, '0')
    if mode == 'encrypt':
        encrypt_file(input_file, output_file, key)
    elif mode == 'decrypt':
        decrypt_file(input_file, output_file, key)
    else:
        raise ValueError('Invalid mode: ' + mode)

这个接口函数提供了加密和解密两种模式，可以根据参数`mode`来选择不同的模式。其中，输入文件的格式应为二进制文件，输出文件同样是二进制文件。主密钥应该以16进制字符串的形式传入，长度应该至少为16个字符，如果长度不是16的整数倍，则会自动补齐。