Digital-asset exchange Quadriga CX has a $200 million problem with no obvious solution — just the latest cautionary tale in the unregulated world of cryptocurrencies.

The online startup can't retrieve about 190 million Canadian dollars ($145 million) in bitcoin, Litecoin, Ether and other digital tokens held for its customers, according to court documents filed Jan. 31 in Halifax, Nova Scotia. Nor can Vancouver-based Quadriga CX pay the CA$70 million in cash they're owed.

Access to Quadriga CX's digital "wallets" — an application that stores the keys to send and receive cryptocurrencies — appears to have been lost with the passing of Quadriga CX Chief Executive Officer Gerald Cotten, who died Dec. 9 in India from complications of Crohn's disease. He was 30.