When you say contract trading I assume you mean leverage trading, through longs and shorts and such.
Anyway, sure! You can short bitcoin on leverage exchanges like BitMEX, and potentially make money when the price drops. If you think it's that easy though? You're wrong. Majority of people trading bitcoin/cryptocurrencies lose their money, and especially when trading on leverage. You might as well go to a casino instead.
Contract trading doesn't mean leverage trading! It means derivative trading which is essentially a contract executed between exchange and the trader where a trader assumes the future price of the underlying assets and locks the contract with the exchange. Read more on the below link,
https://www.investopedia.com/terms/d/derivative.aspTo op, contract trading is mainly used by the seasoned traders. It is structurally more complicated and comes with a fixed date of expiry. It is definitely a good method of speculative trading only if you know the nitty gritties of it!