In multihop networks such as mobile ad hoc networks (MANETs), a node can misbehave by selfishly dropping others' packets to save battery life. This selfishness or misbehaviour can disrupt the whole network functionality and can severely degrade network performance. Reputation based models have been developed to discourage node misbehaviour. However, these models are vulnerable to whitewashing attacks. Whitewashing occurs when a node having poor reputation/trust changes its identity to start afresh and escape from the consequences of its bad actions. This attack can significantly affect the performance of reputation based models. We propose a reputation based scheme for MANETs that acts as a deterrent for whitewashing attacks. Rather than trying to detect whitewashing attacks, we approach the problem in a novel way by removing the advantages that whitewashing can provide. In our proposed scheme, each node must pay an entry fee to consume network services. As monetary fees are not suitable for MANETs due to fee management complications, instead of a monetary fee we use a fee in the form of cooperation. A node will receive services from the network after it cooperates until its reputation is increased to a certain level Y. For a normal selfish node, it is no longer beneficial to perform a whitewash because it will be required to pay the entry fee each time it enters into the network. Simulation results show that our scheme performs well in reducing evil throughput and evil nodes' utility as compared to the CONFIDANT scheme in the presence of whitewashing nodes.