Edward Snowden, who became notorious for exposing the U.S. National Security Agency’s (NSA) massive surveillance agenda in 2013, has said bitcoin’s central flaw may not lie in its transaction rate limitations, but in its public ledger.

Speaking to the audience via webcam at a Blockstack event in Berlin early March, Snowden for the first time gave the audience his detailed views on the emerging technology. While agreeing that bitcoin will endure for a long period of time, Snowden argued that he does not believe “bitcoin will last forever.”

“Everybody is focused on the transaction rate limitations of bitcoin being its central flaw, and that is a major one,” he said, adding that, actually, “the much larger structural flaw, the long-lasting flaw, is its public ledger.”

The whistleblower further explained that the existing mechanism of the bitcoin blockchain has the problem of balancing recording every transaction history with attempting to scale its capacity in processing these transactions.

“That is simply incompatible with having an enduring mechanism for trade, because you cannot have a lifelong history of everyone’s purchases, all of the interactions be available to everyone and have that work out well at scale,” he told the audience.

Talking of his own personal preference in terms of cryptocurrencies, Snowden said:

“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 aired the concern that having a public ledger that documents every transaction history, while it may appeal to a global consumer base, could also draw interest from governments that wish to outlaw the technology.

The comments coincide with reports yesterday of leaked documents suggesting that the NSA may be using its powerful surveillance technology to track, not just the blockchain ledger, but also individual bitcoin users of the distributed network.

Elsewhere, Snowden also raised the issue of cryptocurrency technology being used by dictators in launching state-run projects, such as the Petro token recently issued by the Venezuelan government.

Answering a question over whether he is worried about emerging technologies like blockchain “being co-opted by dictators, by powerful entities, corrupt entities,” Snowden said:

“It’s not a question of if they will be, it’s a question of when they will be. It’s a question of how do we design competing systems that are simply so attractive that they will not be ignored by the global consumer base, but also the governments themselves who are seeking to compete against them will not simply be able to outlaw them and have that be meaningful.”

Edward Snowden image via Blockstack/YouTube