Summary: The retailers within a supply chain management are the most important player as it has direct contact with the customers. Customers are the source of the money and information for the entire supply chain management. The equilibrium condition of the forward and backward supply chain is tight until it is reliable. But sometimes the retailers hide information from the manufacturer and this unreliability starts to propagate to the entire supply chain management. Blockchain technology is one of the secure decentralized systems to prevent unreliability. This study eliminates the unreliability of the system. A mathematical model is derived where the vendor-managed inventory policy is used by the single manufacturer to deal with multiple unreliable retailers. The entire process of manufacturing emits carbon. The carbon emission is controlled by the cap and trade policy and by paying the carbon tax. The results are found by the classical optimization technique and the numerical studies open up a way to the blockchain to deal with unreliable retailers. The decentralized system is a probable choice to prevent unreliability and thus the blockchain.