The nature of mobile ad hoc networks (MANET), demands stringent requirements on primitives that could be used to secure such networks. Mobility imposes restrictions on memory and processor requirements due to limited battery life. The ad hoc nature warrants schemes that could operate for extended periods without referring to a trusted authority (TA). Additionally, any enabling scheme for security should be able to scale well. We introduce a novel key management scheme, RPS - random preloaded subset key distribution - which satisfies all the above requirements. More specifically, RPS is an n-secure r-conference key predistribution scheme. While most of the previously reported key predistribution schemes also meet all the stringent requirements, RPS has many inherent advantages. In this paper we investigate the applicability of RPS in securing MANETs.