Bitcoin Free Cash (BFC) is a new cryptocurrency based on the Cuckoo Cycle algorithm and the Mortgage business model.The main feature of the project is the introduction of the Mortgage mechanism, based on traditional mining, to limit the participation threshold. Thanks to this mechanism, it is possible to effectively avoid the monopoly on electricity, reduce the amount of digital money entering the market, and increase the income of retail miners.Ecosystem safety and reliability provoke stable BFC growth. Thus, the BFC mining mechanism can effectively curb the price drop caused by excessive liquidity.The BFC side mining mechanism allows users to increase retention time and prevent fraudulent activity. Compared to traditional POW mining, BFC can effectively inhibit too fast computing power growth.BFC developed innovative smart contracts based on the Mortgage mechanism to ensure that the blockchain is applied to the real business environment.