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function is not described

PHPMailer\PHPMailer

SMTP::hmac() protected WP 1.0

Calculate an MD5 HMAC hash. Works like hash_hmac('md5', $data, $key) in case that function is not available.

{} It's a method of the class: SMTP{}

No Hooks.

Return

String.

Usage

// protected - for code of main (parent) or child class
$result = $this->hmac( $data, $key );
$data(string) (required)
The data to hash
$key(string) (required)
The key to hash with

Code of SMTP::hmac() WP 5.7.2

<?php
protected function hmac($data, $key)
{
    if (function_exists('hash_hmac')) {
        return hash_hmac('md5', $data, $key);
    }

    //The following borrowed from
    //http://php.net/manual/en/function.mhash.php#27225

    //RFC 2104 HMAC implementation for php.
    //Creates an md5 HMAC.
    //Eliminates the need to install mhash to compute a HMAC
    //by Lance Rushing

    $bytelen = 64; //byte length for md5
    if (strlen($key) > $bytelen) {
        $key = pack('H*', md5($key));
    }
    $key = str_pad($key, $bytelen, chr(0x00));
    $ipad = str_pad('', $bytelen, chr(0x36));
    $opad = str_pad('', $bytelen, chr(0x5c));
    $k_ipad = $key ^ $ipad;
    $k_opad = $key ^ $opad;

    return md5($k_opad . pack('H*', md5($k_ipad . $data)));
}