A micropayment scheme is proposed to enable transactions of different denominations and to eliminate possibilities that either the vendor or the user in a payment system misbehaves to get illegal profit. The proposed offers a solution while keeping transactions efficient.
Hwang, Jing-Jang and Li, Jung-Bin, "A Loss-Free Micropayment Protocol for Multimedia Services" (2002). ICEB 2002 Proceedings. 64.