*7.2. Computation Overhead*

The suggested system is lightweight in terms of communication costs since we only use the time-consuming modulo operation, and each node in the network, such as a sink node, a smart meter, and a home appliance, has at least one modulo operation. The proposed approach will become more efficient if the modulo exponent is computed ahead of time.

**Figure 3.** Communication overhead from sink node to smart meter.

### **8. Future Directions and Challenges**

In this paper, we have discussed smart grids and the relation among different entities of the smart grid and how they interact with each other. After that, we reviewed the literature regarding countermeasures to the posed threats and discussed some promising solutions that are suggested in order to overcome privacy related issues and threats. Lastly, we proposed a novel privacy preservation scheme for HANs. To complete the effort, we have devised a direction for future research and challenges, which are discussed below.

#### *8.1. A Safe and Secure Trust Mechanism for Home Incumbents in Smart Grid*

As discussed in Section 1, smart grids work through the coordination of different entities. The smart gird is a network of different entities and different subnetworks working together. Each entity and subnetwork has its own requirements. The continuous communication is essential to ensure the smart grid remains active. Iinteroperable and uninterrupted communication between the different subnetworks is an intimidating task. Therefore, a universal standardized trusted framework is essential for any communication.

#### *8.2. Government Authorities to Regulate and Maintain Smart Grids*

Most of the research work performed is voluntary and in order to make smart grids a success, it is necessary to have a governmen<sup>t</sup> authority to evaluate the standard and conformity of the research undertaken on smart grids. Thus, the authorities can make the necessary decisions and improvements needed to regulate smart grids.

#### *8.3. New Goals and Standards to Evaluate Privacy Preserving Mechanism and Solution*

The authorities should set standards and new metrics to evaluate any new research or protocols. Each new research idea should be evaluated on common standards and then a decision should be made whether to make it a standard or revise an old standard.

### *8.4. Legal Code for Preserving the Privacy*

A legal framework through the contributions of both governments and business authorities should be made to protect the privacy of consumers and other network entities. The legal framework would help to set the standard to what extent a user's data can be collected and how it can be manipulated to further increase the efficiency of the smart grid. In cases of breach of this contract, the legal framework should outline what the consequences would be faced by the entity breaching the contract.

### *8.5. A Framework for Aggregation without Third Party Involvement*

The third-party involvement in the aggregation can be compromised anytime. A scheme should be devised that could aggregate the data without knowing the meaning of the aggregated data that could not harm or lead the smart grid to instability.
