It is not that without a contract you would have no rights. Most rights (including rent protection) are in fact laid down by law. However, in order to be able to make a claim, you must prove that you rent the house or room in question. Witnesses or bank statements of three months rent payment are generally seen as proof of this. In any case, make sure you can prove that you have paid (a landlord is obliged to give you a receipt if you ask for one). Nevertheless, it is still advisable to sign a tenancy agreement. Standard contracts that you can fill in and use are listed below. This makes it clear to both parties what agreements have been made about payments, maintenance, use of communal areas, and so on. It is also advisable to make a record of the accommodation at the start of the lease. This can prevent a lot of trouble.
Other questions with this subject: