How are these two lines of PHP different?

Question

Assuming that we have salt, which was generated in the database as follows

$salt = time();

What is the difference between these two lines.

$pass1 = hash('sha1', $password . $salt);

$pass2 = hash_hmac('sha1', $password, $salt);

They do not give the same result. The first function hashtakes 2 parameters, and hash_hmac3 parameters. Therefore, you might think that we can get this third additional parameter using $saltseparately (to execute the third parameter), and not concatenate it with the password ( $password . $salt), as in line 2. But this is not so simple, the two results are different. What for? What's going on here?

Answer 1

HMAC SHA-1 SHA-1 . HMAC sha1($salt . sha1($salt . $password)), . Wikipedia HMAC.