In this paper, we propose an efficient scheme that utilizes symmetric-key-cryptography and hashing operations to collect consumption data. The idea is based on sending masked power consumption readings from the meters and removing these masks by adding all the meters' messages, so that the utility can learn the aggregated reading but cannot learn the individual readings. We also introduce a key management procedure that uses asymmetric key operations, but unlike the power consumption collection that is done very frequently, the key management procedure is run every long time for key renewals. Our evaluations indicate that the cryptographic operations needed in our scheme are much more efficient than the operations needed in the existing schemes. In addition, we have shown that the proposed scheme can preserve the consumers' privacy and provide high protection level against collusion attacks. Finally, ns-3 simulation results demonstrate that the network performance of the proposed scheme outperforms the performance of the existing schemes due to reducing the packet size and computational overhead.