Short Sale Attack: A PoW-blockchain-aimed attacking model via short sale

The 51% attack was generally considered to occur at a very small probability when it was first proposed. However, there are more 51% attacks happening recently. With the market price of cryptocurrencies continues to hit a new record recent years, we should also pay attention the higher potential risks accompanied. In this paper, we introduce a new kind of potential 51% attact risk using short sales on PoW-based blockchains and cryptocurrencies. We come out with a model to estimate the upper limit price for a certain cryptocurrency. In particular, we consider the influence of marketing fluctuation and introduce ARIMA to amend the model. Moreover, we discuss some more threatened scene using this kind of attack. Finally, based on the model, we conduct experiments to estimate the price limit and the risk of cryptocurrencies circulating in the current market. Results show that whether large blockchain system(like Bitcoin) or small one (like Ravencoin), they all have varying degrees of risk of being attacked.