python如何实现sm4-ofb加解密算法

SM4是一种国密算法，OFB是一种加密模式，可以将SM4算法和OFB模式结合起来实现SM4-OFB加密算法。下面是一个简单的Python实现：

from Crypto.Cipher import AES
from Crypto.Util.Padding import pad, unpad
import binascii

# SM4算法的S盒
SboxTable = [
    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
]

# SM4算法的T盒
FK = [
    0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc
]

# SM4算法的S盒变换
def Sbox(x):
    return (SboxTable[(x >> 24) & 0xff] << 24) | (SboxTable[(x >> 16) & 0xff] << 16) | \
           (SboxTable[(x >> 8) & 0xff] << 8) | SboxTable[x & 0xff]

# SM4算法的L函数
def L(x):
    return x ^ ((x << 2) | (x >> 30)) ^ ((x << 10) | (x >> 22)) ^ ((x << 18) | (x >> 14)) ^ ((x << 24) | (x >> 8))

# SM4算法的轮函数
def F(x0, x1, x2, x3, rk):
    return x0 ^ L(x1 ^ x2 ^ x3 ^ rk)

# SM4算法的密钥扩展函数
def KeySchedule(key):
    rk = [0] * 32
    k = [0] * 4
    for i in range(4):
        k[i] = (key[(i << 2)] << 24) | (key[(i << 2) + 1] << 16) | (key[(i << 2) + 2] << 8) | key[(i << 2) + 3]
    for i in range(32):
        if i < 16:
            rk[i] = k[i]
        else:
            tmp = rk[i - 1]
            if i % 4 == 0:
                tmp = Sbox(tmp) ^ FK[(i // 4) - 1]
            rk[i] = rk[i - 16] ^ tmp
    return rk

# SM4算法的加密函数
def Encrypt(input, key):
    rk = KeySchedule(key)
    ct = [0] * 4
    pt = [0] * 4
    for i in range(4):
        pt[i] = (input[(i << 2)] << 24) | (input[(i << 2) + 1] << 16) | (input[(i << 2) + 2] << 8) | input[(i << 2) + 3]
    for i in range(32):
        ct[0], ct[1], ct[2], ct[3] = F(pt[0], pt[1], pt[2], pt[3], rk[i])
        pt[0], pt[1], pt[2], pt[3] = ct[0], ct[1], ct[2], ct[3]
    output = [0] * 16
    for i in range(4):
        output[(i << 2)] = ct[i] >> 24
        output[(i << 2) + 1] = (ct[i] >> 16) & 0xff
        output[(i << 2) + 2] = (ct[i] >> 8) & 0xff
        output[(i << 2) + 3] = ct[i] & 0xff
    return output

# SM4算法的解密函数
def Decrypt(input, key):
    rk = KeySchedule(key)
    ct = [0] * 4
    pt = [0] * 4
    for i in range(4):
        ct[i] = (input[(i << 2)] << 24) | (input[(i << 2) + 1] << 16) | (input[(i << 2) + 2] << 8) | input[(i << 2) + 3]
    for i in range(31, -1, -1):
        pt[0], pt[1], pt[2], pt[3] = F(ct[0], ct[1], ct[2], ct[3], rk[i])
        ct[0], ct[1], ct[2], ct[3] = pt[0], pt[1], pt[2], pt[3]
    output = [0] * 16
    for i in range(4):
        output[(i << 2)] = ct[i] >> 24
        output[(i << 2) + 1] = (ct[i] >> 16) & 0xff
        output[(i << 2) + 2] = (ct[i] >> 8) & 0xff
        output[(i << 2) + 3] = ct[i] & 0xff
    return output

# OFB加密模式
def OFB_Encrypt(data, key, iv):
    cipher = []
    block = iv
    for i in range(len(data) // 16):
        block = Encrypt(block, key)
        cipher_block = [data[j] ^ block[j] for j in range(16)]
        cipher.extend(cipher_block)
    return cipher

# OFB解密模式
def OFB_Decrypt(cipher, key, iv):
    data = []
    block = iv
    for i in range(len(cipher) // 16):
        block = Encrypt(block, key)
        data_block = [cipher[j] ^ block[j] for j in range(16)]
        data.extend(data_block)
    return data

# 测试代码
if __name__ == '__main__':
    key = binascii.unhexlify('0123456789abcdeffedcba9876543210')
    iv = binascii.unhexlify('0123456789abcdef')
    data = b'This is a test message'
    data = pad(data, 16)
    cipher = OFB_Encrypt(data, key, iv)
    print(binascii.hexlify(cipher))
    plain = OFB_Decrypt(cipher, key, iv)
    plain = unpad(plain, 16)
    print(plain)

以上代码实现了SM4算法和OFB加密模式的结合，可以进行SM4-OFB加解密。