The Citadel CEO spoke with CNBC about GameStop and bitcoin. : Ken Griffin, who runs a sprawling Wall Street empire that includes market making operations and a hedge fund, was dismissive of cryptocurrencies even as some see the emerging asset as the future of finance. "I just don't spend much time thinking about cryptocurrencies ... I don't see the economic underpinning of cryptocurrencies. I understand how to value a stock -- the net present value of earnings -- I understand how to think about currency exchange rates around the world," Griffin said to Andrew Ross Sorkin on CNBC's "Squawk Box."