public function key($key)
    {
        $this->key = self::hkdf($key, 'KeyForEncryption');
        $this->authentication = self::hkdf($key, 'KeyForAuthentication');

        return $this;
    }
public function key($key)
    {
        $this->key = self::hkdf($key, 'KeyForEncryption');
        $this->authentication = self::hkdf($key, 'KeyForAuthentication');

        return $this;
    }
public function key ( $ key ) { $ this -> key = self :: hkdf ( $ key , 'KeyForEncryption' ) ; $ this -> authentication = self :: hkdf ( $ key , 'KeyForAuthentication' ) ; return $ this ; }
Set the keys to encrypt and authenticate.

@param string $key The binary key

@return self
Set the keys to encrypt and authenticate .