SM4介绍
SM4算法是一种对称加密算法，也被称为国密算法。它是由中国密码学家设计的，已被列入国家密码局的标准。
SM4算法使用128位的密钥和分组大小，使用32轮迭代加密，可以用于加密数据和验证消息认证码。它的加密效率很高，安全性也很好，被广泛应用于各种安全领域，如电子商务、移动通信和云计算等。
算法实现流程图
加密算法
密钥扩展算法
其中，K0~K3的生成过程如下：
设输入的密钥为MK=（MK0，MK1，MK2，MK3），则（K0，K1，K2，K3）=（MK0 ^ FK0，MK1 ^ FK1，MK2 ^ FK2，MK3 ^ FK3）
注：
- CKi以及FKi为常数；
- i 的取值为 i=0,1,…31,共生成32个子密钥。
源码
加密
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
]
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
]
def wd_to_byte(wd, bys):
bys.extend([(wd >> i) & 0xff for i in range(24, -1, -8)])
def bys_to_wd(bys):
ret = 0
for i in range(4):
bits = 24 - i * 8
ret |= (bys[i] << bits)
return ret
def s_box(wd):
"""
进行非线性变换，查S盒
:param wd: 输入一个32bits字
:return: 返回一个32bits字 ->int
"""
ret = []
for i in range(0, 4):
byte = (wd >> (24 - i * 8)) & 0xff
row = byte >> 4
col = byte & 0x0f
index = (row * 16 + col)
ret.append(S_BOX[index])
return bys_to_wd(ret)
def rotate_left(wd, bit):
"""
:param wd: 待移位的字
:param bit: 循环左移位数
:return:
"""
return (wd << bit & 0xffffffff) | (wd >> (32 - bit))
def Linear_transformation(wd):
"""
进行线性变换L
:param wd: 32bits输入
"""
return wd ^ rotate_left(wd, 2) ^ rotate_left(wd, 10) ^ rotate_left(wd, 18) ^ rotate_left(wd, 24)
def Tx(k1, k2, k3, ck):
"""
密钥扩展算法的合成变换
"""
xor = k1 ^ k2 ^ k3 ^ ck
t = s_box(k1 ^ k2 ^ k3 ^ ck)
return t ^ rotate_left(t, 13) ^ rotate_left(t, 23)
def T(x1, x2, x3, rk):
"""
加密算法轮函数的合成变换
"""
t = x1 ^ x2 ^ x3 ^ rk
t = s_box(t)
return t ^ rotate_left(t, 2) ^ rotate_left(t, 10) ^ rotate_left(t, 18) ^ rotate_left(t, 24)
def key_extend(main_key):
MK = [(main_key >> (128 - (i + 1) * 32)) & 0xffffffff for i in range(4)]
# 将128bits分为4个字
keys = [FK[i] ^ MK[i] for i in range(4)]
# 生成K0~K3
RK = []
for i in range(32):
t = Tx(keys[i + 1], keys[i + 2], keys[i + 3], CK[i])
k = keys[i] ^ t
keys.append(k)
RK.append(k)
return RK
def R(x0, x1, x2, x3):
# 使用位运算符将数值限制在32位范围内
x0 &= 0xffffffff
x1 &= 0xffffffff
x2 &= 0xffffffff
x3 &= 0xffffffff
s = f"{x3:08x}{x2:08x}{x1:08x}{x0:08x}"
return s
def encode(plaintext, rk):
X = [plaintext >> (128 - (i + 1) * 32) & 0xffffffff for i in range(4)]
for i in range(32):
t = T(X[1], X[2], X[3], rk[i])
c = (t ^ X[0])
X = X[1:] + [c]
ciphertext = R(X[0], X[1], X[2], X[3])
# 进行反序处理
return ciphertext
def decode(ciphertext, rk):
ciphertext = int(ciphertext, 16)
X = [ciphertext >> (128 - (i + 1) * 32) & 0xffffffff for i in range(4)]
for i in range(32):
t = T(X[1], X[2], X[3], rk[31 - i])
c = (t ^ X[0])
X = X[1:] + [c]
m = R(X[0], X[1], X[2], X[3])
return m
def output(s, name):
out = ""
for i in range(0, len(s), 2):
out += s[i:i + 2] + " "
print(f"{name}:", end="")
print(out.strip())
if __name__ == '__main__':
plaintext = 0x0123456789abcdeffedcba9876543210
main_key = 0x0123456789abcdeffedcba9876543210
rk = key_extend(main_key)
print("加密:")
ciphertext = encode(plaintext, rk)
output(ciphertext, "ciphertext")
print("解密:")
m = decode(ciphertext, rk)
output(m, "plaintext")
解密
由于SM4算法是对合运算，因此解密算法与加密算法相同，只是轮密钥的使用顺序相反。
运行结果
加密:
ciphertext:68 1e df 34 d2 06 96 5e 86 b3 e9 4f 53 6e 42 46
解密
plaintext:01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 10
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