Edward Snowden, who is known for revealing sensitive information about the U.S. National Security Agency’s (NSA), said that he believes Bitcoin will eventually be replaced by another cryptocurrency which does not use a public ledger.

Snowden, who made this statement earlier in March at a Blockstack event in Berlin, disclosed to the audience via webcam what he thought were Bitcoin’s main flaw, which has nothing to do with its transaction rate limitations, but rather its lack of privacy.

“Everybody is focused on the transaction rate limitations of bitcoin being its central flaw, and that is a major one, but I would argue that the much larger structural flaw, the long-lasting flaw, is its public ledger,” said Snowden. “That is simply incompatible with having an enduring mechanism for trade, because you cannot have a lifelong history of everyone’s purchases, all of their interactions be available to everyone and have that work out well at scale.”

“I don’t think Bitcoin will last forever,” stated Snowden, who implied that he was using Bitcoin in 2013 to hide his identity during preparations for the release of the National Security Agency (NSA) files which documented privacy abuses — including those that showed NSA’s surveillance activity on Bitcoin users.

“Bitcoin does important work and I do think it will have enduring value for a long time, but particularly when we look at the core development team and their rate of improvement to the protocol, they simply need to better or they will not be able to compete,” he continued.

The whistleblower said that he is most interested in cryptocurrencies that are more focused on privacy, such as Zcash, which obfuscate blockchain data to enable users to check the validity of transactions while keeping them away from prying eyes.

“When we talk about which cryptocurrencies are interesting to me, I’ve said it before and I’ll say it again, Zcash for me is the most interesting right now, because the privacy properties of it are truly unique, but we see more and more projects that are trying to emulate this and I think this is a positive thing.”

Snowden also mentioned that he also tested Monero and other privacy-centric crypto coins, though in past statements he said he preferred Zcash seeing as it was developed by academic cryptographers.