The high concentration in crypto trading on a handful of exchanges, with Binance alone accounting for about half the market, raises concerns about the impact of a failure on the sector, the EU's securities watchdog said on Wednesday.

The bloc is rolling out the world's first comprehensive set of rules to regulate trading in cryptoassets such as bitcoin, Ether and Tether, requiring exchanges to be authorised.

The European Securities and Markets Authority's detailed analysis of what's being traded and by whom found that so far the euro currency plays only a minor role.

Trading volumes are highly concentrated, with 10 exchanges processing about 90% of trades, and the largest, Binance, accounting for about half the market.

"While this might be advantageous from an efficiency standpoint due to economies of scale, it raises considerable concerns regarding the implications of a failure or malfunction at a major asset or exchange for the wider crypto ecosystem," ESMA said.

"We observe that the market concentration among exchanges has increased over time, and that Binance alone accounts for more than 50% of trading volume."

Binance said in a statement that it believes that the healthy and sustainable growth of the crypto industry is a key responsibility for the company and other players in the market.

"Our focus continues to be on... continuing to invest in compliance processes for a new era of regulatory certainty," Binance said.

Bitcoin hit an all-time high of $73,803.25 in March, but the total value of all cryptocurrencies - $2.7 trillion, according to CoinGecko - still represents a tiny fraction of the global financial system.

ESMA said identifying the origin of order flow or the geographic location of crypto exchanges remains problematic, with about 55% of current global trading volumes executed on exchanges that hold an EU licence.

Most transactions occur outside the bloc at exchanges domiciled in tax havens, ESMA said.

"Contrary to the frequent claim that crypto assets could represent a safe haven in times of wider market stress, we find a certain co-movement with equities and no stable relationship with gold," ESMA said.

ESMA will hold a webinar on April 25 to discuss its findings.

(Reporting by Huw Jones; Additional reporting by Elizabeth Howcroft; Editing by Alex Richardson, Jan Harvey and Jonathan Oatis)