Depending on the target weight

Restrict carbohydrates to 20 grams per day or less - a strict low carb diet. No need to restrict fiber, this can be even beneficial.

Restricts the protein to moderate levels. It is possible to keep us in 1 gram of protein per day, per kilo of weight. If you weigh 70 kilos (https://fitcrasher.com), the equivalent would be about 70 grams of protein.

It could be beneficial in fact to decrease it even more, especially for people with some overweight, targeting 1 g of protein per kilo depending on the target weight https://fitcrasher.com. The main error that prevents many people from remaining in optimal state of ketosis is consuming too much protein.