Is subscribing to a pension scheme, in which you pay an annual sum and then receive a larger sum upon retirement age, impermissible?

Insurance is of two types: Commercial, which is forbidden, based on gharar (excessive uncertainty/risk) and profiteering; and Takaful (cooperative), which is permissible, based on cooperation and collective bearing of risks, and not for the purpose of profiteering. If the company is commercial, it is not permissible to subscribe to it, but if it is Takaful, then it is permissible.