The communication message between the access system and the XX characteristic prefix adopts the newspaper MAC signature, and the signature is used to identify the legitimacy of the source and whether the newspaper format has been tampered with or destroyed. The steps to generate the MAC signature value are as follows:

After consulting colleagues, the company has ready-made MD5 encryption method in crypt library;

Decisively reuse! ! !

Verification: According to the standard md5 algorithm, the string "123456" should be E10ad3949ba59abe 56E057F20F883e.

There are three related to MD5 in crypt library:

Verification 1:- is inconsistent.

Verification 2:- Continuous availability

Call encryption machine SM4 algorithm to encrypt and decrypt data.

Keyboard encoder

-every two bits of data are byte compressed.

-Compress data into bytes.

-decoding: the first 16 bytes obtained.

-decoding: the first 17-32 bytes are converted into bytes.