You want to set a new application key.
php artisan key:generate command.
$ php artisan key:generate Application key [Idgz1PE3zO9iNc0E3oeH3CHDPX9MzZe3] set successfully.
You shouldn't need to do this.
When you first create your Laravel application,
key:generate is automatically called.
So it should already be set for you.
If you change it by executing the command again, be aware that passwords saved with
Hash::make() will no longer be valid.