# 算法介绍

SM4 算法于 2012 年被国家密码管理局确定为国家密码行业标准，最初主要用于 WAPI (WLAN Authentication and Privacy Infrastructure) 无线网络中。SM4 算法的出现为将我国商用产品上的密码算法由国际标准替换为国家标准提供了强有力的支撑。随后，SM4 算法被广泛应用于政府办公、公安、银行、税务、电力等信息系统中，其在我国密码行业中占据着及其重要的位置。类似于 DES、AES 算法，SM4 算法也是一种分组密码算法。

# 原理介绍

SM4 算法的原理可以参考该博文 点击此处跳转

SM4 的官方文档 点击此处跳转

# 具体代码(python)

class SM4Cipher:
def __init__(self, key: bytes):
if not len(key) == 16:
raise ValueError("SM4 key must be length of 16. ")
self._key_r = self._generate_key(key)
self.block_size = 16

def encrypt(self, plaintext: bytes):
return self._do(plaintext, self._key_r)

def decrypt(self, ciphertext: bytes):
return self._do(ciphertext, self._key_r[::-1])

def _do(self, text: bytes, key_r: list):
text_ = [0 for _ in range(4)]
# 将 128bit 转化成 4x32bit
for i in range(4):
text_[i] = int.from_bytes(text[4 * i:4 * i + 4], 'big')
for i in range(32):
box_in = text_[1] ^ text_[2] ^ text_[3] ^ key_r[i]
box_out = self._s_box(box_in)
temp = text_[0] ^ box_out ^ self._rot_left(box_out, 2) ^ self._rot_left(box_out, 10)
temp = temp ^ self._rot_left(box_out, 18) ^ self._rot_left(box_out, 24)
text_ = text_[1:] + [temp]
text_ = text_[::-1]  # 结果逆序
# 将 4x32bit 合并成 128bit
result = bytearray()
for i in range(4):
result.extend(text_[i].to_bytes(4, 'big'))
return bytes(result)

def _generate_key(self, key: bytes):
"""密钥生成"""
key_r, key_temp = [0 for _ in range(32)], [0 for _ in range(4)]
FK = [0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc]
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]
# 将 128bit 拆分成 4x32bit
for i in range(4):
temp = int.from_bytes(key[4 * i:4 * i + 4], 'big')
key_temp[i] = temp ^ FK[i]
# 循环生成轮密钥
for i in range(32):
box_in = key_temp[1] ^ key_temp[2] ^ key_temp[3] ^ CK[i]
box_out = self._s_box(box_in)
key_r[i] = key_temp[0] ^ box_out ^ self._rot_left(box_out, 13) ^ self._rot_left(box_out, 23)
key_temp = key_temp[1:] + [key_r[i]]
return key_r

@staticmethod
def _s_box(n: int):
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]
result = bytearray()
# 将 32bit 拆分成 4x8bit，依次进行S盒变换
for item in list(n.to_bytes(4, 'big')):
result.append(BOX[item])
return int.from_bytes(result, 'big')

@staticmethod
def _rot_left(n, m):
"""循环左移"""
return ((n << m) | (n >> (32 - m))) & 0xFFFFFFFF


# 测试样例及结果

key = bytes.fromhex("0123456789ABCDEFFEDCBA9876543210")  # 128bit密钥
plaintext = bytes.fromhex("00112233445566778899aabbccddeeff")  # 128bit明文
sm4 = SM4Cipher(key)
print(sm4.encrypt(plaintext).hex())  # 09325c4853832dcb9337a5984f671b9a

# 样例一
key = "0123456789ABCDEFFEDCBA9876543210"  # 16进制字符串
plaintext = "0123456789ABCDEFFEDCBA9876543210"  # 16进制字符串
ciphertext = "681edf34d206965e86b3e94f536e4246"  # 16进制字符串

# 样例二
key = "0123456789ABCDEFFEDCBA9876543210"  # 16进制字符串
plaintext = "00112233445566778899aabbccddeeff"  # 16进制字符串
ciphertext = "09325c4853832dcb9337a5984f671b9a"  # 16进制字符串

# 样例三
key = "456789ABCDEFFEDCBA98765432100123"  # 16进制字符串
plaintext = "2233445566778899aabbccddeeff0011"  # 16进制字符串
ciphertext = "58ab414d84fb3008b0bee987f97021e6"  # 16进制字符串

# 样例四
key = "89ABCDEFFEDCBA987654321001234567"  # 16进制字符串
plaintext = "445566778899aabbccddeeff00112233"  # 16进制字符串
ciphertext = "5937a929a2d9137216c72a28cd9cf619"  # 16进制字符串


posted @ 2021-07-20 11:59  kentle  阅读(4557)  评论(0编辑  收藏  举报