Former U.S. Trading Commissioner Bart Chilton has said that bitcoin isn’t a fraud, but that it’s a sustainable currency.

His comments are in response to former Federal Reserve Chairman Alan Greenspan who recently raised concerns about the digital currency’s sustainability. According to Fox Business, Greenspan said:

Human nature is such that if you get something such as Bitcoin, you think there is some value there, whether there is or there isn’t.

Chilton, however, believes in the cryptocurrency. So much so, that he responded by saying:

I do think it’s sustainable, I don’t know if it’s sustainable at these prices. I mean, the only difference is, with Chairman Greenspan is that, you know, people are willing to pay for it and so if they’re willing to pay for it there is a demand.

Critics, though, have spoken out against bitcoin. The most famous is Jamie Dimon, JPMorgan Chase CEO, who said in September that the digital currency was ‘a fraud,’ adding that it was ‘worth nothing.’

Chilton added:

I don’t think it’s, you know, a fraud, like Jamie Dimon said, or a pyramid scheme like President Putin said, I mean, people are actually using Bitcoins to purchase things. So, that’s not a scam or a fraud.

Over the last week, bitcoin has seen its value fall from $7,800 down to $5,500. Yet, despite dropping in price by 29 percent, it has since recovered. According to CoinMarketCap, it is currently trading at over $6,600. However, Chilton believes that when the CME Group launch their bitcoin futures by the end of the year it will bring regulation to the cryptocurrency market.

He stated:

The CME group which has done a great job. You know I used to regulate them all the time so I have a pretty good sense of what they do, you know, that is actually going to go ahead and regulate these things, put some side boards on it.

Despite this, though, the CEO of Societe Generale doesn’t believe bitcoin has no future due to its anonymity and because governments are continually working at regulating them.