The mastermind of one of the biggest ever cryptocurrency heists should be jailed for five years for a money laundering conspiracy linked to a $6 billion hack on the Bitfinex exchange, U.S. prosecutors told a judge. The government said in a court filing on Tuesday that Ilya Lichstan, who pleaded guilty last year, should spend more time in prison than his rapper wife and co-conspirator, Heather Morgan, who prosecutors said last week should be sentenced to 18 months in prison. Prosecutors said Mr. Lichenstein fit the profile of young cybercriminals whose online activities were "normalized in a way that downplayed the impact on victims."