Hedge fund billionaire Ken Griffin and former U.S. President Donald Trump have both slammed digital currencies as a threat to the U.S. dollar. Griffin, the founder of the $38 billion hedge fund Citadel LLC, told the Economic Club of Chicago on Oct. 4, that crypto is "a jihadist call that we don't believe in the dollar."  He expressed his dismay over the younger generation working on dollar alternatives in the crypto sector: "I wish all this passion and energy that went to crypto was directed towards making the United States stronger," he added.