The rising cryptocurrency boom has sparked a fundraising scheme called initial coin offerings that have become a money-pumping machine for startups but also have a problematic reputation.

Masahiro Yasu, 29, chief executive officer of Tokyo-based startup Alis Co., experienced the power of the ICO when his firm raised ?100 million in virtual currencies in just four minutes last March.

¡°We were confident of our business plan . . . but we were surprised when we could actually attract that much money that quickly,¡± Yasu said in an interview last month, adding that his firm successfully raised its goal of over ?400 million in about 10 days.