Jim Chanos, who predicted the fall of Enron, has serious doubts about the legitimacy of bitcoin.

"This is simply a security speculation game masquerading as a technological breakthrough in monetary policy," Chanos in an interview with the Institute for New Economic Thinking published this week.

Chanos, who teaches a course on the history of financial fraud at Yale University, says the mania around cryptocurrency following bitcoin's rise near $20,000 last year fits into what he calls the "fraud cycle."

Bitcoin has been compared it to "digital gold," because some see it as a store of value, and it has a limited supply. Apple co-founder Steve Wozniak told CNBC in an interview this week that he "totally buys into" that comparison and the phrase "pure digital gold."

Chanos challenged that store-of-value case, saying that in an "apocalypse" food would actually function better as a currency.

"In the worst-case scenario, that's exactly the case in which a digital currency will work the least," Chanos said. "The last thing I'd want to own is bitcoin if the grid goes down."

Others see bitcoin as a viable currency, with no lender of last resort or third party adjudicator. While it can be used to transact, it's more appealing to those looking to dodge government oversight, he said.

"Bitcoin is still the area for people who are trying to avoid taxation or other examinations of their transactions," said Chanos, who founded New York-based Kynikos Associates. "That's one thing where I think it probably still has utility, but the governments have figured that out."

Some fraudsters have been emboldened by the fundraising craze known as initial coin offerings, or ICOs. The SEC has cracked down on the process with subpoenas and charges against some celebrity-backed projects this year. ICOs raised $6.6 billion in 2017 and have hit $9.1 billion this year, according to the most recent research firm Autonomous Next.

"I suspect going forward we're going to see more and more evidence of questionable companies as this bull market keeps advancing and aging," Chanos said.

The short-seller has rallied against bitcoin before, calling it "speculative mania."

"It's Beanie Babies," he said at a Schechter event in Detroit, Michigan, referring to the collectible toy craze during the 1990s.