Energy market trading systems are undergoing rapid transformation due to an increasing demand for renewable energy sources to be integrated into the power grid, coupled with the dynamic and evolving needs of future energy customers. In the current energy trading system, which is based on mega power generation, energy is traded by insecure means of communication based on mutual trust. In addition, electricity from both renewable and non-renewable sources is mixed in the grid, impeding customers' ability to definitively track the source of energy dispatched to their premises. Although blockchain technology has been studied for energy trading on a peer-to-peer microgrid trading, to our knowledge none of the previous work focused on using blockchain for trading energy in a national wholesale energy market in macrogrid. In this paper, we address security architectures required of the energy market trading system in an Australian context, we propose a cryptocurrency token-based structure and a smart contract that provides data confidentiality that verifies and audits transactional records. The proposed trading system architecture not only enhances overall system security but provides additional capabilities in the operation of the scheme so that sources of energy dispatched to customer premises are known. The energy market trading system we propose also presents higher security compared to existing trading systems.