python gmssl SM4不填充加解密

问题描述

 使用gmssl(python版本)进行SM4加/解密时结果与国标(GMT0002)不符，或解密失败，原因是gmssl默认使用PKCS7填充，国标文档里的样例是没有填充的。

解决方法

方法一：创建CryptSM4对象时将填充模式设为-1。这是笔者推荐的方法。

方法二：使用CryptSM4.one_round。这是个底层函数，每次只能加/解密一个分组。

例程

from gmssl import sm4, func
 
g_sData = '0123456789abcdeffedcba9876543210'
g_sKey = '0123456789abcdeffedcba9876543210'
 
 
def main():
    bufData = bytes.fromhex(g_sData)
    bufKey = bytes.fromhex(g_sKey)
 
    oSM4 = sm4.CryptSM4()
    oSM4.set_key(bufKey, sm4.SM4_ENCRYPT)
    r = oSM4.crypt_ecb(bufData)
    print(f'enc:{r.hex()}')
 
    oSM4 = sm4.CryptSM4(sm4.SM4_ENCRYPT, sm4.PKCS7)
    oSM4.set_key(bufKey, sm4.SM4_ENCRYPT)
    r = oSM4.crypt_ecb(bufData)
    print(f'enc:{r.hex()}')
 
    oSM4 = sm4.CryptSM4(sm4.SM4_ENCRYPT, sm4.ZERO)
    oSM4.set_key(bufKey, sm4.SM4_ENCRYPT)
    r = oSM4.crypt_ecb(bufData)
    print(f'enc:{r.hex()}')
 
    oSM4 = sm4.CryptSM4(sm4.SM4_ENCRYPT, -1)  # 方法1
    oSM4.set_key(bufKey, sm4.SM4_ENCRYPT)
    r = oSM4.crypt_ecb(bufData)
    print(f'enc:{r.hex()}')
    oSM4.set_key(bufKey, sm4.SM4_DECRYPT)
    r = oSM4.crypt_ecb(r)
    print(f'dec:{r.hex()}')
 
    oSM4 = sm4.CryptSM4()  # 方法2
    oSM4.set_key(bufKey, sm4.SM4_ENCRYPT)
    r = oSM4.one_round(oSM4.sk, bufData)
    r = func.list_to_bytes(r)
    print(f'enc:{r.hex()}')
    oSM4.set_key(bufKey, sm4.SM4_DECRYPT)
    #r = func.bytes_to_list(r)
    r = oSM4.one_round(oSM4.sk, r)
    r = func.list_to_bytes(r)
    print(f'dec:{r.hex()}')
 
    return
 
 
if __name__ == '__main__':
    main()

例程输出：

enc:681edf34d206965e86b3e94f536e4246002a8a4efa863ccad024ac0300bb40d2
enc:681edf34d206965e86b3e94f536e4246002a8a4efa863ccad024ac0300bb40d2
enc:681edf34d206965e86b3e94f536e42462677f46b09c122cc975533105bd4a22a
enc:681edf34d206965e86b3e94f536e4246
dec:0123456789abcdeffedcba9876543210
enc:681edf34d206965e86b3e94f536e4246
dec:0123456789abcdeffedcba9876543210

注意事项

sm4.ZERO是一个名字叫“ZERO”的填充模式，不是不填充。

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