The ProShares Bitcoin Strategy ETF /zigman2/quotes/230440344/composite BITO +0.37% was trading higher Tuesday morning, in its debut on the New York Stock Exchange, marking a milestone for the nascent crypto sector. The ProShares fund, up 2.6%, is the first ETF that offers exposure to bitcoin /zigman2/quotes/31322028/realtime BTCUSD -2.79% , a virtual asset that has only existed since 2009. The offering from ProShares comes after a number of proposals to launch a bitcoin ETF that were rejected by the Securities and Exchange Commission. Comments in the summer from SEC Chairman Gary Gensler, suggesting that he might be receptive to approving an ETF that was pegged to futures contracts, paved to way for fund providers to propose a futures-linnked ETF. Gensler has said that futures offer investors greater protections than a fund that is linked to bitcoin directly. Futures are derivative financial contracts that provide investors exposure to price moves in an underlying asset. However, the value of futures contracts sometimes diverge from the underlying asset, which is one of a number of criticisms of a bitcoin futures ETF.