US whistleblower Edward Snowden voiced concerns over Bitcoin’s long-term prospects in an interview on March 22, saying the cryptocurrency’s public Blockchain made it susceptible to abuse.

Speaking via webcam in an interview with Coin Center director of research Peter Van Valkenburgh at the Blockstack Berlin 2018 conference, Snowden agreed Bitcoin’s ledger was “devastatingly public.”

“The much larger structural flaw, the long-lasting flaw, is its public ledger,” he said of Bitcoin, adding that he nonetheless “may” have used it to buy server infrastructure in 2013.

Bitcoin’s future remains a hot topic of debate this year as technical improvements to its network increasingly allow it to be used as an instant, near-free currency once again.

This week, Twitter CEO Jack Dorsey told mainstream media that he foresees a “single currency” for the internet coming within ten years. “I personally believe that it will be Bitcoin,” he added.

For Snowden, however, a true alternative to fiat currencies that balances mass appeal with lack of government control has yet to surface: