用python实现sm4

SM4是一种对称加密算法，主要用于数据的加密和解密。下面是一个Python实现SM4加密算法的示例代码：

# -*- coding: utf-8 -*-
"""
SM4加密算法实现
"""

import struct


# S盒
S_BOX = [
    0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7, 0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05,
    0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3, 0xaa, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99,
    0x9c, 0x42, 0x50, 0xf4, 0x91, 0xef, 0x98, 0x7a, 0x33, 0x54, 0x0b, 0x43, 0xed, 0xcf, 0xac, 0x62,
    0xe4, 0xb3, 0x1c, 0xa9, 0xc9, 0x08, 0xe8, 0x95, 0x80, 0xdf, 0x94, 0xfa, 0x75, 0x8f, 0x3f, 0xa6,
    0x47, 0x07, 0xa7, 0xfc, 0xf3, 0x73, 0x17, 0xba, 0x83, 0x59, 0x3c, 0x19, 0xe6, 0x85, 0x4f, 0xa8,
    0x68, 0x6b, 0x81, 0xb2, 0x71, 0x64, 0xda, 0x8b, 0xf8, 0xeb, 0x0f, 0x4b, 0x70, 0x56, 0x9d, 0x35,
    0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, 0xd1, 0xa2, 0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, 0x87,
    0xd4, 0x00, 0x46, 0x57, 0x9f, 0xd3, 0x27, 0x52, 0x4c, 0x36, 0x02, 0xe7, 0xa0, 0xc4, 0xc8, 0x9e,
    0xea, 0xbf, 0x8a, 0xd2, 0x40, 0xc7, 0x38, 0xb5, 0xa3, 0xf7, 0xf2, 0xce, 0xf9, 0x61, 0x15, 0xa1,
    0xe0, 0xae, 0x5d, 0xa4, 0x9b, 0x34, 0x1a, 0x55, 0xad, 0x93, 0x32, 0x30, 0xf5, 0x8c, 0xb1, 0xe3,
    0x1d, 0xf6, 0xe2, 0x2e, 0x82, 0x66, 0xca, 0x60, 0xc0, 0x29, 0x23, 0xab, 0x0d, 0x53, 0x4e, 0x6f,
    0xd5, 0xdb, 0x37, 0x45, 0xde, 0xfd, 0x8e, 0x2f, 0x03, 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b, 0x51,
    0x8d, 0x1b, 0xaf, 0x92, 0xbb, 0xdd, 0xbc, 0x7f, 0x11, 0xd9, 0x5c, 0x41, 0x1f, 0x10, 0x5a, 0xd8,
    0x0a, 0xc1, 0x31, 0x88, 0xa5, 0xcd, 0x7b, 0xbd, 0x2d, 0x74, 0xd0, 0x12, 0xb8, 0xe5, 0xb4, 0xb0,
    0x89, 0x69, 0x97, 0x4a, 0x0c, 0x96, 0x77, 0x7e, 0x65, 0xb9, 0xf1, 0x09, 0xc5, 0x6e, 0xc6, 0x84,
    0x18, 0xf0, 0x7d, 0xec, 0x3a, 0xdc, 0x4d, 0x20, 0x79, 0xee, 0x5f, 0x3e, 0xd7, 0xcb, 0x39, 0x48
]

# 系统参数
FK = [
    0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc
]

# 固定参数
CK = [
    0x00070e15, 0x1c232a31, 0x383f464d, 0x545b6269,
    0x70777e85, 0x8c939aa1, 0xa8afb6bd, 0xc4cbd2d9,
    0xe0e7eef5, 0xfc030a11, 0x181f262d, 0x343b4249,
    0x50575e65, 0x6c737a81, 0x888f969d, 0xa4abb2b9,
    0xc0c7ced5, 0xdce3eaf1, 0xf8ff060d, 0x141b2229,
    0x30373e45, 0x4c535a61, 0x686f767d, 0x848b9299,
    0xa0a7aeb5, 0xbcc3cad1, 0xd8dfe6ed, 0xf4fb0209,
    0x10171e25, 0x2c333a41, 0x484f565d, 0x646b7279
]


def get_u32_be(data):
    """
    获取4字节的大端序整数
    """
    return struct.unpack('>I', data)[0]


def put_u32_be(num):
    """
    将4字节的整数转换成大端序字节数组
    """
    return struct.pack('>I', num)


def sm4_key_schedule(key):
    """
    SM4密钥扩展
    """
    rk = [0] * 32
    k = [0] * 4

    k[0] = get_u32_be(key[0:4])
    k[1] = get_u32_be(key[4:8])
    k[2] = get_u32_be(key[8:12])
    k[3] = get_u32_be(key[12:16])

    for i in range(32):
        if i < 16:
            rk[i] = k[i % 4] ^ FK[i]
        else:
            a = rk[i - 2]
            b = rk[i - 1]
            c = rk[i - 15]
            d = rk[i - 16]
            tmp = (a ^ b ^ c ^ CK[i - 16]) & 0xffffffff
            rk[i] = (tmp << 13 | tmp >> 19) ^ (rk[i - 7] << 3 | rk[i - 7] >> 29) ^ (rk[i - 14] << 9 | rk[i - 14] >> 23)

    return rk


def sm4_f(x0, x1, x2, x3, rk):
    """
    SM4轮函数
    """
    # T盒变换
    t = x1 ^ x2 ^ x3 ^ rk
    a = b = c = d = 0

    for i in range(8):
        a = (t >> 24) & 0xff
        b = (t >> 16) & 0xff
        c = (t >> 8) & 0xff
        d = t & 0xff
        index = (a << 16 | b << 8 | c) << 1
        y = S_BOX[index] << 24 | S_BOX[index + 1] << 16 | S_BOX[index + 2] << 8 | S_BOX[index + 3]
        t = y ^ ((t << 13 | t >> 19) ^ (t << 23 | t >> 9))

    # 线性变换
    r = (t >> 24) & 0xff | (t >> 8) & 0xff00 | (t << 8) & 0xff0000 | (t << 24) & 0xff000000
    return r ^ x0


def sm4_encrypt_block(input_data, rk):
    """
    SM4加密单个分组
    """
    x = [0] * 4
    x[0] = get_u32_be(input_data[0:4])
    x[1] = get_u32_be(input_data[4:8])
    x[2] = get_u32_be(input_data[8:12])
    x[3] = get_u32_be(input_data[12:16])

    for i in range(32):
        tmp = x[1] ^ x[2] ^ x[3] ^ rk[i]
        x[0] = sm4_f(x[0], x[1], x[2], x[3], rk[i])
        x[0], x[1], x[2], x[3] = tmp, x[0], x[1], x[2]

    # 将加密后的4个32位整数转换成16字节的字节数组
    return put_u32_be(x[3]) + put_u32_be(x[2]) + put_u32_be(x[1]) + put_u32_be(x[0])


def sm4_encrypt(key, input_data):
    """
    SM4加密
    """
    rk = sm4_key_schedule(key)
    input_data_len = len(input_data)
    block_count = (input_data_len + 15) // 16  # 计算分组数量
    output_data = b''

    # 对每个分组进行加密
    for i in range(block_count):
        block_data = input_data[i * 16:(i + 1) * 16]
        if len(block_data) < 16:
            padding_len = 16 - len(block_data)
            block_data += bytes([padding_len] * padding_len)
        output_data += sm4_encrypt_block(block_data, rk)

    return output_data


if __name__ == '__main__':
    key = b'0123456789abcdef'
    input_data = b'Hello, SM4!'
    output_data = sm4_encrypt(key, input_data)
    print(output_data.hex())

示例中实现了SM4加密算法的核心部分，使用时需要调用 `sm4_encrypt` 函数，传入密钥和要加密的数据。加密后的数据以字节串的形式返回。