Investors frustrated by the absence of cryptocurrency exchange traded funds can try the next best thing -- funds investing in blockchain, the ledger technology at the heart of all digital coins. Canada has approved its first blockchain ETF, joining a handful already trading in the U.S. Harvest Portfolios Group's Blockchain Technology ETF (HBLK) is listed on the Toronto Stock Exchange and charges a management fee of 0.65%. The fund tracks a proprietary index of large and emerging companies working with blockchain technology. Four blockchain-oriented ETFS are available in the U.S, although regulations there prevent them from using the term in the name. Reality Shares NexGen Economy ETF (BLCN) and Amplify Transformational Data Sharing ETF (BLOK) launched in mid-January, and have already attracted more than $100 million in investment. The First Trust Indxx Innovative Transaction & Process ETF (LEGR) and Innovation Shares NextGen Protocol ETF (KOIN) launched more recently. Management fees for the four ETFs range between 0.65% and 0.70%. At this point, there are no pure-play blockchain technology companies that are publicly traded. Instead, the ETFs invest in big tech firms such as Nvidia (NVDA), whose chips are used to mine cryptocurrencies, and Microsoft (NASDAQ:MSFT), which has a number of blockchain initiatives underway. U.S. regulators have withheld approval of cryptocurrency ETFS because of concerns about volatility and liquidity.