With the development of high speed computer networks, video service on the Web has huge market potential in that the video service can be provided to subscribers with greater time and schedule exibility compared to the current cable TV system. Under the pay-perview (PPV) scheme, subscribers only need to pay for the programs that they have watched. A critical issue on PPV service is the capability of settling disputes over PPV service charges. This is especially important in the case that the Internet communication could be interrupted (by accident or deliberately) in the middle of a viewing session. This paper proposes a fair PPV billing protocol for web-based video service. With this protocol, a video service will be divided into small units, and a subscriber needs to submit cryptographic evidence which enables fair billing based on the number of units being provided in a viewing session. In addition, by the establishment of a one-way sequential link, the validity of evidence is maint...