// HMAC encryption
//Use a secret key to encrypt the data and do two hashes
//The secret key comes from the server
//1, send an account, the server generates a key (secret key), the server saves the account, the key corresponding to the account, key Encrypt plaintext (HMAC password) for the client, send it to the server to save, and the registration is successful.
//2. Use the existing key (secret key) to encrypt the account, with the key, HMAC password, and account area server verification.
//3. Do: (1) Send an account to the server, request a key (2), encrypt and verify, and save the key locally.
// The key leak is only for one user.
//4. Use 32-bit string encryption, simulate login, 32-bit HMAC password + send time server to verify twice (1-2 minutes before the received time)
// MD5 query http://www.cmd5.com /
//Use a secret key to encrypt the data and do two hashes
//The secret key comes from the server
//1, send an account, the server generates a key (secret key), the server saves the account, the key corresponding to the account, key Encrypt plaintext (HMAC password) for the client, send it to the server to save, and the registration is successful.
//2. Use the existing key (secret key) to encrypt the account, with the key, HMAC password, and account area server verification.
//3. Do: (1) Send an account to the server, request a key (2), encrypt and verify, and save the key locally.
// The key leak is only for one user.
//4. Use 32-bit string encryption, simulate login, 32-bit HMAC password + send time server to verify twice (1-2 minutes before the received time)
// MD5 query http://www.cmd5.com /